Unit One Chapter Four 3rd SEC. Quiz 3

The immune system carries out defense by producing antibodies. Antibodies are proteins that are produced by specialized cells in the immune system called B cells. These antibodies bind to specific foreign substances, such as bacteria or viruses, and help to neutralize or eliminate them from the body. This is an important mechanism of defense in the immune system, as it helps to identify and target harmful invaders. Secretion of toxins, camouflage, and running to escape are not specific mechanisms of defense carried out by the immune system.

T-suppressor cells, also known as CD8+ T cells, play a role in regulating the immune response. They can bind to CD8 receptors found on the surface of T-helper cells, plasma cells, and T-cytotoxic cells. This binding allows T-suppressor cells to interact with these cells and modulate their activity, helping to maintain immune balance and prevent excessive immune responses.

Plasma cells are a type of white blood cell that produce and secrete antibodies, not interferon protein. Interferon is a protein that is released by cells in response to viral infection, and it plays a key role in the body's immune response to viruses. T-lymphocytes, macrophages, and viral infected-cells are all capable of secreting interferon protein as part of the immune response. Therefore, the correct answer is plasma cells.

Antibodies are proteins produced by plasma cells in response to an infection. They work by binding to specific antigens on the surface of pathogens, such as viruses, and marking them for destruction by the immune system. However, in the case of viral infections, antibodies may not be able to destroy infected cells because they are too large to enter the cells and directly neutralize the virus. Instead, other immune cells, such as cytotoxic T cells, are needed to recognize and eliminate the infected cells. Therefore, the correct answer is that antibodies are relatively large sized molecules that cannot reach the virus inside the cell.

When a cell is infected by a virus, it releases interferon as a defense mechanism to inhibit the replication of the virus in neighboring cells. Interferon is a type of protein that is produced by cells in response to viral infection. It acts by binding to neighboring cells and inducing a series of antiviral responses, such as inhibiting viral protein synthesis and activating immune cells to attack the virus. This helps to limit the spread of the virus to other cells and prevent further infection.

Humoral-mediated immunity refers to the immune response that involves the production of antibodies by B cells. These antibodies are then released into the body fluids, such as blood and lymph, to target and neutralize antigens and pathogens. This type of immunity is particularly effective against extracellular pathogens, which are present in body fluids rather than inside cells. Therefore, the correct answer is body fluids.

The primary immune response is the initial response of the immune system to an antigen. It involves the activation and proliferation of B cells, which then differentiate into plasma cells that produce antibodies. This process takes time as the immune system needs to recognize the antigen, activate the appropriate immune cells, and generate a sufficient number of antibodies. Therefore, it is reasonable to expect that the primary immune response would take several days to a few weeks to reach peak antibody production.

Lymphokines increased by decreasing plasma B cells because lymphokines are signaling molecules produced by activated T cells, and they play a role in regulating the immune response. When plasma B cells decrease, it means that there is a decrease in the production of antibodies. Lymphokines are involved in the activation and differentiation of B cells, so when plasma B cells decrease, the production of lymphokines increases to compensate and stimulate the immune response.

Humoral-mediated immunity is a type of immune response that involves the production and circulation of antibodies. Antibodies are proteins produced by specialized cells called B cells, which are part of the immune system. These antibodies are released into the bloodstream and other body fluids, such as saliva and mucous, to help neutralize and eliminate pathogens. Therefore, the correct answer is "The antibodies" because they play a crucial role in humoral-mediated immunity.

Ts-cells start their action at point (B).

After being activated by Helper T-cells, B-cells undergo a process called clonal expansion, where they divide and multiply rapidly. This allows for the production of a large number of B-cells, which can then differentiate into plasma cells or memory B-cells. The plasma cells are responsible for producing and secreting antibodies, while the memory B-cells help to provide long-term immunity by "remembering" the specific antigen and quickly responding to future infections.

Perforin is the correct answer because it is a protein released by the immune system cell (such as a cytotoxic T cell or natural killer cell) to destroy infected cells. It creates pores in the cell membrane of the infected cell, leading to its destruction and elimination. In the given figure, X is most likely representing the release of perforin by the immune system cell to attack and destroy the virus-infected body cell.

The correct sequence of the immune response is as follows: Activated helper T-cells release interleukin, which activates B-cells. Activated B-cells then differentiate into plasma cells, which produce antibodies. Therefore, the correct sequence is Activated helper T-cells – interleukin – activated B-cells – plasma cells – antibodies.

B-cells adhere to their antigen by immune receptors. Immune receptors are proteins on the surface of B-cells that recognize and bind to specific antigens. When an immune receptor on a B-cell binds to its corresponding antigen, it triggers a series of events that activate the B-cell and initiate an immune response. This binding is crucial for the B-cell to recognize and respond to foreign invaders, such as bacteria or viruses, and produce antibodies to neutralize them. MHC (major histocompatibility complex) molecules are involved in presenting antigens to T-cells, not in the direct adherence of B-cells to antigens. CD4 is a protein found on helper T-cells, which plays a role in the immune response, but it is not directly involved in the adherence of B-cells to antigens.

The diagram shows the beginning of an immune response, which involves T lymphocytes. Among the given options, Helper-T cells are the ones that play a crucial role in coordinating and regulating the immune response. They help activate other immune cells, such as B cells and cytotoxic T cells, by releasing chemical signals called cytokines. This activation is important for the immune system to effectively eliminate pathogens. Therefore, the correct answer is Helper-T cells.

In a non-specific immune response, the correct sequence of events is as follows:
A (Recognition of pathogen or antigen) ⟶ D (Activation of immune cells) ⟶ B (Inflammatory response) ⟶ C (Phagocytosis) ⟶ E (Elimination of pathogen or antigen). This sequence represents the correct order of events in a non-specific immune response.

B-lymphocytes are an example of specific immunity because they are a type of white blood cell that plays a key role in the adaptive immune response. B-lymphocytes are responsible for producing antibodies, which are proteins that specifically target and neutralize pathogens or foreign substances in the body. This targeted response is characteristic of specific immunity, as it allows the immune system to recognize and respond to specific threats in a highly specific manner.

Activated helper T-cells secrete proteins called interleukins. Interleukins are a group of cytokines that act as signaling molecules between immune cells. They play a crucial role in regulating the immune response by promoting the activation, proliferation, and differentiation of other immune cells. Interleukins also help in coordinating the immune response by mediating communication between different types of immune cells. Therefore, the secretion of interleukins by activated helper T-cells is essential for the proper functioning of the immune system.

Cytokines are small proteins that play a crucial role in cell signaling during immune responses. They are involved in various functions such as attracting immune cells to the site of infection, activating immune cells like natural killer cells and macrophages, and coordinating the immune response. However, stimulating plasma cells to produce antibodies is not a function of cytokines. Plasma cells are activated by B lymphocytes through a process called antigen presentation and T cell help. Cytokines may indirectly support this process by promoting the activation and proliferation of B lymphocytes, but they do not directly stimulate plasma cells to produce antibodies.

B-lymphocytes are a type of white blood cell that are responsible for producing antibodies. They have the ability to divide and differentiate into two types of cells: plasma cells, which produce and secrete antibodies, and memory cells, which "remember" a specific pathogen and provide long-term immunity. This division and differentiation process allows B-lymphocytes to effectively respond to and eliminate infections in the body. Natural killer cells, monocytes, and macrophages do not undergo this type of division and differentiation.

Macrophages and B-cells are capable of binding to the CD4 receptors found on the surface of T-helper cells. This binding is important for the activation of T-helper cells and the initiation of an immune response. Macrophages are antigen-presenting cells that can present antigens to T-helper cells, while B-cells can interact with T-helper cells to receive signals for antibody production. Therefore, both macrophages and B-cells play crucial roles in the immune response by binding to CD4 receptors on T-helper cells.

Tears possess a defense mechanism that protects the body because they contain antimicrobial substances. These substances help to kill or inhibit the growth of microorganisms, such as bacteria, on the surface of the eye. This defense mechanism helps to prevent eye infections and maintain the overall health of the eye.

Fragments of antigens will bind to a protein called Major histocompatibility complex inside the macrophage. The Major histocompatibility complex is responsible for presenting the antigen fragments to T cells, which triggers an immune response. This process helps the immune system identify and eliminate foreign substances in the body.

T-helper cells are activated when they bind to an antigen-presenting cell that displays a specific processed antigen on its surface. This interaction is crucial for the immune response as it allows the T-helper cell to recognize the antigen and initiate a cascade of immune reactions. The other options, such as bacterial toxins, mast cells, complement proteins, and extracellular antigens, are not directly involved in the activation of T-helper cells.

The nonspecific immune response refers to the general defense mechanisms that the body has in place to prevent and fight against infections, such as inflammation and fever. These responses are not specific to a particular antigen and can be activated quickly. On the other hand, the specific immune response is a targeted response that is tailored to a specific antigen, such as a virus or bacteria. This response takes longer to develop as it involves the production of specific antibodies and immune cells. Therefore, the nonspecific immune response is faster than the specific immune response.

The correct answer states that humoral immunity responds to extracellular pathogens, while cell-mediated immunity responds to intracellular pathogens. This means that humoral immunity is responsible for targeting pathogens that are outside of the body's cells, such as bacteria and viruses in the bloodstream or tissues. On the other hand, cell-mediated immunity is involved in targeting pathogens that have infected the body's cells, such as viruses that have entered and replicated within a host cell. This differentiation in the type of pathogens targeted is a key difference between the two types of immunity.

The correct answer is that cloned T cells cannot differentiate into histamine-producing cells and help regulate the inflammatory response. T cells are primarily involved in cell-mediated immunity and do not produce histamine. Histamine is mainly released by mast cells and basophils during an inflammatory response. T cells can perform various functions such as activating cytotoxic T cells, stimulating B cells, and stimulating phagocytes, but they do not play a role in producing histamine.

The figure shows that the peak of the primary immune response to antigen A occurs at a later time compared to the peak of the secondary immune response to antigen A. Therefore, the primary response takes approximately twice as long to peak as the secondary response.

Plasma cells are the end-stage effector cells of B-cells, which means they are responsible for producing and secreting antibodies. The B-cell is indeed the precursor of the plasma cell, as it undergoes differentiation to become a plasma cell. However, plasma cells do not have surface receptors. Instead, they are specialized for antibody production and secretion, and their cytoplasm is filled with rough endoplasmic reticulum (RER) to support high levels of protein synthesis.

Histamine is released during an inflammatory response to an injury. It causes dilation of blood vessels, leading to increased blood flow to the injured area. This increased blood flow helps to deliver immune cells and nutrients to aid in the healing process. Histamine also increases capillary permeability, allowing fluid and immune cells to move out of the blood vessels and into the surrounding tissues. This helps to create an inflammatory response and promote healing.

T-cytotoxic cells, also known as cytotoxic T cells or killer T cells, are the most effective immune cells at destroying intracellular pathogens. These cells are able to recognize infected cells and directly kill them by releasing toxic substances. T-cytotoxic cells play a crucial role in the body's immune response against viral infections and other intracellular pathogens. They are able to identify and destroy infected cells, preventing the spread of the pathogen and promoting the clearance of the infection.

Cytotoxic (Killer) T cells are a type of immune cell that specifically target and destroy virally infected cells. These cells recognize the infected cells by detecting the presence of viral antigens on their surface. Once identified, the cytotoxic T cells release toxic substances that induce cell death in the infected cells, effectively eliminating the virus from the body.

After clonal selection, T-helper cells do not directly ingest extracellular pathogens by phagocytosis. Their main functions include forming memory cells, stimulating clonal proliferation of specific B cells, stimulating macrophages to carry out phagocytosis, and activating cytotoxic T cells to attack infected body cells.

Memory T-helper cells provide protection against a second infection of the same virus by rapidly stimulating cell-mediated and humoral immune responses. This means that they activate both the cellular and antibody-mediated immune responses, which work together to eliminate the virus and prevent its spread in the body. By doing so, memory T-helper cells help to mount a faster and more effective immune response, leading to a quicker clearance of the virus and providing long-term immunity against future infections.

The statement "Cells of this system are antigen-specific" does not describe the response of the nonspecific (innate) immune system. The nonspecific immune system does not rely on antigen specificity and instead provides a generalized defense against a wide range of pathogens. This system includes inflammation following tissue injury, an immediate response to infection, triggering complement proteins in the blood plasma, and the involvement of neutrophils and macrophages.

T-lymphocytes are a type of white blood cell that play a crucial role in cell-mediated immunity. They directly attack and destroy infected cells or cancer cells in the body. This type of immune response does not involve the production of antibodies by plasma cells or the release of antigens by bacteria. The reaction between antigens and antibody molecules is part of the humoral immune response, which is mediated by B-lymphocytes. Therefore, the correct answer is cell-mediated immunity.

The second line of defense starts by a severe inflammation. This suggests that there are multiple lines of defense, and the second line is initiated by inflammation. This implies that the first line of defense is something other than inflammation, and the third line of defense is not mentioned as starting with inflammation. Therefore, the correct answer is Second.

Ciliated epithelial cells in the respiratory tract have tiny hair-like structures called cilia that beat in coordinated waves. This movement helps to move mucus, dust particles, and pathogens out of the respiratory system. By continuously moving these substances away from the lungs, ciliated epithelial cells play a crucial role in preventing infections and maintaining the health of the respiratory system.

Activated T-cells are a type of immune cell that plays a crucial role in the body's defense against viral infections. When T-cells encounter viral infected cells, they release interferons. Interferons are proteins that help to inhibit viral replication and spread by interfering with the virus's ability to infect new cells. They also stimulate the immune response by activating other immune cells and enhancing their ability to kill virus-infected cells. Therefore, the correct answer is Interferon.

The secondary immune response occurs when the body is exposed to a pathogen that it has encountered before. During the primary immune response, memory cells are created to "remember" the pathogen. When the body is exposed to the same pathogen again, the memory cells quickly recognize it and initiate a rapid and more effective immune response. This is why the secondary immune response is much faster than the first immune response. Additionally, the presence of memory cells allows for a quicker elimination of the pathogen, resulting in little to no symptoms of the disease.

Graph A expresses the relation between the amount of mucus and the amount of antibodies when we caught flu.

When an organism's body cells have been infected by a virus, cell-mediated immunity would be initiated. This is because cell-mediated immunity is the branch of the immune response that involves the activation of T cells, which are responsible for directly attacking infected cells. In this situation, the infected body cells would present viral antigens on their surface, which would be recognized by specific T cells. These T cells would then be activated and differentiate into cytotoxic T cells, which can directly kill the infected cells and prevent the spread of the virus.

Lysozyme is an enzyme that is found in saliva and tears. Its function is to hydrolyze or break down the cell wall of invading bacteria. This helps to weaken and destroy the bacteria, preventing them from causing infection or spreading further in the body.

When a memory B cell encounters a complementary antigen, it undergoes both multiplication and differentiation. It multiplies to produce more memory B cells, which helps to enhance the immune response. Additionally, it also differentiates into plasma cells, which are responsible for producing large amounts of antibodies to neutralize the antigen. This dual response of multiplication and differentiation ensures a robust and effective immune response against the specific antigen.

Cell X in the figure is a neutrophil. Neutrophils are a type of white blood cell that are part of the immune system's response to infection and tissue injury. They are typically the first cells to arrive at the site of injury and are responsible for engulfing and destroying bacteria and other foreign substances. Neutrophils are characterized by their multi-lobed nucleus and granular cytoplasm. In the given figure, cell X exhibits these characteristics, indicating that it is a neutrophil.

Antibodies are found in level (C) of immunity. Antibodies, also known as immunoglobulins, are proteins produced by the immune system in response to the presence of foreign substances called antigens. They play a crucial role in the adaptive immune response by recognizing and binding to specific antigens, thereby marking them for destruction by other immune cells. Antibodies are an essential component of humoral immunity, which is one of the two main branches of the immune system. They are produced by B cells and are capable of neutralizing pathogens, promoting their elimination from the body.

Histamine is a substance released by cells in response to injury, infection, or allergic reactions. It is known to cause inflammation by dilating blood vessels and increasing blood flow to the affected area. This increased blood flow leads to redness, swelling, and warmth, which are characteristic signs of inflammation. Therefore, histamine is one of the inflammation-generating substances mentioned in the question.

The correct answer is "Activates the T-helper cells, and they divide rapidly by mitosis." When the T-helper lymphocyte binds to the antigen presented by the MHC on the macrophage, it activates the T-helper cells. This activation leads to the rapid division of these cells through mitosis. This division allows for the production of more T-helper cells, which play a crucial role in coordinating the immune response against the pathogenic bacteria.

Subcellular structure X in the process of phagocytosis in a macrophage contains hydrolytic enzymes. These enzymes are responsible for breaking down the engulfed pathogens or foreign particles during phagocytosis. They help in the digestion and degradation of the internalized material, allowing the macrophage to eliminate the threat effectively.

Memory cells are a type of immune cell that are formed during the first immune response. They can live for tens of years and may survive until death. Memory cells do not function in each of the first and the second immune response. Instead, they remain dormant until they encounter the same pathogen again, at which point they quickly divide to produce large amounts of antibodies to fight off the infection.

Cell-mediated immunity is carried out by T cells, while humoral immunity is mainly carried out by B cells. T cells play a crucial role in cell-mediated immunity by directly attacking and destroying infected cells or cancer cells. They also help in the activation of other immune cells. On the other hand, B cells are responsible for humoral immunity, which involves the production of antibodies. B cells differentiate into plasma cells that secrete antibodies, which can neutralize pathogens and mark them for destruction by other immune cells. Therefore, T cells and B cells have distinct roles in the immune response, with T cells being involved in cell-mediated immunity and B cells in humoral immunity.

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Natural killer cells are a type of lymphocyte that play a role in the immune response against viral infections and tumors. They are able to kill target cells by releasing proteolytic proteins, such as perforin and granzymes, which induce apoptosis in the target cells. This ability to release proteolytic proteins is what allows natural killer cells to kill infected or abnormal cells.

During a non-specific immune response, T-cells do not produce any substances. Non-specific immune responses are the body's immediate defense mechanisms against pathogens and do not involve the production of specific antibodies or substances by T-cells. T-cells mainly play a role in specific immune responses, where they produce substances such as cytokines and cytotoxic molecules to target specific pathogens. Therefore, the correct answer is zero.

The diagram shows the interaction between B-cells, B-memory cells, and B-plasma cells. B-cells are a type of white blood cell that produce antibodies. B-memory cells are a type of B-cell that "remember" previous infections and can quickly produce antibodies upon re-exposure to the same pathogen. B-plasma cells are another type of B-cell that produce and secrete large amounts of antibodies. Therefore, the correct order of the cells in the diagram is B-cells, B-memory cells, and B-plasma cells.

Mast cells and basophils are both types of white blood cells that are involved in the immune response. They secrete inflammation-generating substances such as histamine and cytokines, which can cause redness, swelling, and pain at the site of an injury or infection. This inflammatory response is an important part of the body's defense against pathogens, but it can also contribute to tissue damage and disease if it becomes chronic or excessive.

NK cells, also known as natural killer cells, are lymphocytes that participate in innate immunity. They are a type of cytotoxic lymphocyte that play a crucial role in the early response to viral infections and tumors. NK cells are able to recognize and kill infected or abnormal cells without prior sensitization, making them an important component of the innate immune system. B-cells, TH cells, and TC cells are all involved in adaptive immunity rather than innate immunity.

Cytotoxic T cells are specialized immune cells that target and destroy infected or abnormal cells in the body. They recognize specific antigens displayed on the surface of these cells and initiate a response to eliminate them. In this case, a toxin released by a bacterium is not a target for cytotoxic T cells because it is not a living cell. Cytotoxic T cells primarily target cells that are infected with pathogens, cancerous, or transplanted cells, as they pose a threat to the body's health.

After reacting with antigen molecules, B-lymphocytes of the immune system undergo a transformation and convert into plasma cells. These plasma cells then secrete antibodies, which are proteins that help in neutralizing and eliminating the antigens from the body. This process is an essential part of the adaptive immune response to protect the body against pathogens.

The difference between cell-mediated and humoral immunity is that humoral immunity responds to extracellular pathogens, such as bacteria and viruses that are outside of cells, while cell-mediated immunity responds to intracellular pathogens, such as viruses that have entered and are replicating within cells. This is because humoral immunity primarily involves the production of antibodies that can neutralize or eliminate pathogens in the extracellular environment, while cell-mediated immunity involves the activation of T cells that can directly kill infected cells or activate other immune cells to eliminate intracellular pathogens.

The correct answer is "Memory cells that bind to antigen A and antigen B and plasma cells for antigen A." This is because the graph shows an increase in antibody concentration for both antigen A and antigen B at time (t). Memory cells are responsible for recognizing and binding to specific antigens, so memory cells that bind to both antigen A and antigen B would be present. Additionally, plasma cells are responsible for producing antibodies, so plasma cells for antigen A would also be present to account for the increase in antibody concentration for antigen A.

Cytotoxic T-cells use perforin to puncture the membrane of pathogens. Perforin is a protein that forms pores in the target cell's membrane, allowing for the entry of other molecules and ultimately leading to the destruction of the pathogen. This mechanism is an important defense mechanism of the immune system, as it allows the cytotoxic T-cells to directly attack and eliminate infected or abnormal cells.

From the figure, it can be deduced that a sample cultured from an infected animal causes a similar disease when injected into a healthy one. This suggests that the disease is caused by a pathogen, as the same pathogens, after growing in culture, can cause different diseases when injected into the same type of animals. This supports Koch's approach of identifying the cause of a disease by demonstrating that it can be reproduced in a healthy animal through injection of the cultured pathogen.

Histamine is a chemical compound released by mast cells and basophils in response to injury or inflammation. When released, histamine causes the blood vessels to dilate at the site of injury, leading to increased blood flow to the area. This increased blood flow helps to bring in immune cells and other factors necessary for the healing process. Therefore, histamine is responsible for dilating the blood vessels at the place of injury.

Cytotoxic T-cells induce "cellular suicide" to pathogen cells by secreting lymphatic toxins. These toxins are released by the T-cells and cause damage to the pathogen cells, leading to their destruction. This mechanism is an important part of the immune response and helps to eliminate infected cells from the body.

Helper T cells are a type of white blood cell that play a crucial role in activating both the humoral and cellular immune responses. They help coordinate and regulate the immune system by releasing chemical signals that stimulate other immune cells, such as B cells and cytotoxic T cells, to mount an immune response against pathogens. Helper T cells are essential for the production of antibodies by B cells, which is a key component of the humoral immune response. Additionally, they also help activate cytotoxic T cells, which are responsible for directly killing infected cells and enhancing the cellular immune response.

When the person is infected with the rhinovirus, their immune system will mount a primary immune response to fight off the infection. This response will produce antibodies that specifically target the rhinovirus. However, these antibodies will not be effective against the measles virus because it is a different pathogen with different antigens. Therefore, when the person is subsequently infected with the measles virus, their immune system will not be able to mount a secondary immune response, as it does not have memory cells or antibodies that are specific to the measles virus.

Raw A describes the features of passive immunity.

The lag phase of the secondary immune response is usually much shorter than the lag phase of the primary immune response. This is because during the primary immune response, the immune system is encountering the pathogen for the first time and needs time to recognize it and mount an effective response. However, during the secondary immune response, the immune system has already encountered the pathogen before and has memory cells that can quickly recognize and mount a response against it. Therefore, the lag phase is shorter in the secondary immune response.

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The primary immune response is slow because of the absence of T and B-memory cells. Memory cells are a crucial component of the immune system as they "remember" previous encounters with a specific pathogen. During a primary immune response, the body is encountering a pathogen for the first time, so there are no memory cells to quickly recognize and respond to the pathogen. This results in a slower immune response as the immune system needs time to identify the pathogen, activate the appropriate immune cells, and produce antibodies to fight off the infection.

Plasma cells are not involved in the cell-mediated immune response because they are responsible for producing and secreting antibodies, which are part of the humoral immune response. Cell-mediated immune response involves the activation of T cells, such as cytotoxic T cells, T memory cells, and T-helper cells, which directly target and destroy infected cells. Macrophages are also involved in the cell-mediated immune response as they phagocytize pathogens and present antigens to T cells.

The secondary immune response is faster and more efficient than the primary immune response because the body has already been exposed to the antigen before. During the secondary immune response, memory B cells quickly recognize the antigen and initiate antibody production. This process usually takes a few days to reach peak antibody production.

The correct answer is that the primary immune response occurs after a person is exposed to an antigen for the first time. This means that the immune system recognizes the antigen as foreign and mounts a response to eliminate it. This response includes the production of specific antibodies and the activation of immune cells to target and destroy the pathogen. Subsequent exposures to the same antigen will result in a secondary immune response, which is faster and more effective due to the presence of memory cells that were generated during the primary response.

The diagram illustrates the sequence of events in the immune response to the coronavirus. The first graph (A) represents the adaptive response, which is the body's specific immune response to the virus. This involves the production of antibodies and activation of T cells to target and eliminate the virus. The second graph (B) represents viral replication, which is the process by which the virus reproduces and spreads within the body. The third graph (C) represents the innate response, which is the body's immediate, non-specific defense mechanism against the virus. This includes the activation of natural killer cells and the release of inflammatory molecules. Therefore, the correct order of the graphs is adaptive response, viral replication, and innate response.

The presence of specific antibodies to the virus in a person's blood would be the best indicator that they have had a complete primary immune response to the virus. Antibodies are produced by the immune system in response to an infection, and they specifically target and neutralize the virus. Therefore, the presence of specific antibodies indicates that the person's immune system has recognized and successfully fought off the virus, making them potentially immune.

Histamine is an example of a chemical signal secreted by cells during the start of an immune response in the 2nd line of defense. Histamine is released by mast cells and basophils in response to injury or allergens, and it plays a role in inflammation and allergic reactions. It causes blood vessels to dilate, leading to increased blood flow to the area, and also increases the permeability of blood vessels, allowing immune cells to move more easily to the site of infection or injury.

After the early stage in the humoral immune response, the next step is that a T-helper cell binds to the MHC-antigen complex. This interaction is crucial for the activation of B cells. The T-helper cell recognizes the antigen presented by the MHC complex on the surface of an antigen-presenting cell (APC) and binds to it. This binding activates the T-helper cell, which then releases cytokines, such as interleukin 2, to stimulate the proliferation and differentiation of B cells. This ultimately leads to the production and secretion of antibodies by the B cells to target and neutralize the antigen.

T-cells are not phagocytic cells. Phagocytic cells are responsible for engulfing and destroying pathogens or foreign particles. Monocytes, B-cells, and macrophages are all examples of phagocytic cells. T-cells, on the other hand, are a type of lymphocyte that play a key role in the immune response by recognizing and attacking specific pathogens or infected cells. They do not have the ability to engulf and destroy particles like phagocytic cells do.

Natural killer cells and macrophages are involved in the second and third line of defense. Natural killer cells are a type of lymphocyte that can directly kill infected or cancerous cells. Macrophages are a type of white blood cell that engulfs and destroys pathogens. Both of these cells play important roles in the immune response and are part of the body's defense against infections and diseases.

The figure represents the immune response, with two different components represented by letters X and Y. The correct answer states that letter X represents the primary immune response, while letter Y represents perforin. Perforin is a substance involved in the secondary immune response, which plays a role in the destruction of infected cells. Therefore, the answer choice "Secondary - perforin" correctly identifies the substance represented by letter Y in the figure.

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The CD8 co-receptor is predominantly expressed on the surface of cytotoxic T-cells (CT cells) and natural killer (NK) cells. This co-receptor plays a crucial role in the immune response by binding to major histocompatibility complex class I (MHC-I) molecules on target cells. This interaction enhances the recognition and killing of infected or abnormal cells by CT cells and NK cells. Helper T-cells, on the other hand, primarily express the CD4 co-receptor and have a different role in the immune response.

Goblet cells are mucus-secreting cells that are present in mucus membranes throughout the body. The purpose of the mucus they release is to trap pathogens and other foreign particles. However, the skin is not a mucus membrane and does not contain goblet cells. Therefore, the correct answer is Skin.

The graph shows that the concentration of antibodies in the blood increases immediately after the first dose of vaccination and then gradually decreases over time. This indicates that memory cells are produced during the initial period of 0-7 days after the first dose, as the concentration of antibodies is highest during this time. Additionally, the graph shows a second increase in antibody concentration after the second dose of vaccination, which occurs between 28-35 days. Therefore, memory cells are also produced during this period.

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Graph A represents the steps of the adaptive immune response when a person is exposed to the same pathogen more than once. This is because the graph shows an initial response with low antibody levels, followed by a secondary response with higher antibody levels. This pattern is characteristic of the adaptive immune response, where the body's immune system remembers previous exposure to a pathogen and mounts a faster and stronger response upon re-exposure.

The innate defense system includes the inflammatory response, which is a non-specific defense mechanism that occurs in response to tissue injury or infection. During the inflammatory response, various cellular and chemical components are activated to eliminate the harmful stimuli and initiate the healing process. This response involves the release of inflammatory mediators, such as histamine and cytokines, which cause vasodilation, increased vascular permeability, and recruitment of immune cells to the site of injury or infection. The inflammatory response is an important component of the innate immune system and plays a crucial role in protecting the body from pathogens.

The correct answer is Macrophages and granulated cells. Macrophages are a type of immune cell that engulfs and destroys pathogens and cellular debris. Granulated cells refer to cells that contain granules in their cytoplasm, such as mast cells or eosinophils, which are involved in allergic reactions and defense against parasites. Monocytes are precursors to macrophages and are not the same as macrophages themselves. Cytotoxic T cells are a type of immune cell that directly kills infected or cancerous cells. Natural killer cells are another type of immune cell that kills infected or cancerous cells, while helper T cells assist in coordinating immune responses. Therefore, the correct answer is Macrophages and granulated cells.

The correct answer is "Third" because acquired immunity is the third line of defense against microbes. The first line of defense is the physical and chemical barriers of the body, such as the skin and mucous membranes. The second line of defense is the innate immune response, which includes inflammation and the activation of immune cells. Acquired immunity, also known as adaptive immunity, is the third line of defense and involves the production of specific antibodies and immune cells to target and eliminate specific pathogens.