Immunology Multiple Choice Questions

Phagocytosis refers to the process in which cells engulf and destroy particulate matter. This process is commonly observed in immune cells, such as macrophages and neutrophils, which engulf and digest pathogens, cellular debris, and other foreign substances. Therefore, the statement that cellular ingestion and destruction of particulate matter are called phagocytosis is true.

Chemotaxis refers to the directed movement of cells in response to chemical signals. It allows cells to navigate towards or away from specific chemicals in their environment. This process is crucial for various biological processes such as immune response, wound healing, and embryonic development. Therefore, the statement that the directional movement of cells in response to chemicals is called chemotaxis is true.

The immune system is responsible for recognizing foreign molecules and taking appropriate actions to neutralize or destroy them. It plays a crucial role in defending the body against infections and diseases. The integumentary system is primarily responsible for protecting the body from external threats but does not specifically recognize and respond to foreign molecules. The renal system is responsible for filtering waste from the blood but does not have a direct role in recognizing and responding to foreign molecules. The lymphatic system is involved in immune responses, but it is not the specific system responsible for recognizing foreign molecules. Therefore, the correct answer is the immune system.

Antibodies are indeed soluble proteins that are secreted by plasma cells. They play a crucial role in the immune system by recognizing and binding to specific antigens, such as bacteria or viruses, to neutralize them and facilitate their elimination from the body. Antibodies are produced in response to the presence of foreign substances in the body and are an essential component of the adaptive immune response. Therefore, the statement that soluble proteins secreted by plasma cells are called antibodies is true.

The immune response is the third line of defense because it is a complex system that involves the activation of specialized cells and molecules to recognize and destroy pathogens. It is a specific response that targets specific antigens and can adapt to different pathogens. The immune response includes both innate and adaptive immunity, which work together to eliminate pathogens and prevent reinfection. This line of defense is crucial in protecting the body against various diseases and infections.

The first line of defense in the immune response includes the skin and mucous membranes. These physical barriers act as a protective barrier against pathogens, preventing them from entering the body. The skin acts as a physical barrier, while the mucous membranes produce mucus that traps pathogens and prevents them from entering the body. Both of these components work together to prevent the entry of harmful microorganisms and protect the body from infection.

T cells are a type of white blood cells that play a crucial role in the immune response. There are several types of T cells, including cytotoxic, helper, and regulatory T cells. Cytotoxic T cells are responsible for killing infected cells, while helper T cells assist in coordinating the immune response. Regulatory T cells help to suppress the immune response and maintain tolerance. Antigenic is not a recognized type of T cell. Antigens are molecules that can trigger an immune response, but they are not a specific type of T cell.

The correct answer is "Immune Response" because the adaptive defense system refers to the body's ability to recognize and respond to specific pathogens or foreign substances. This response involves the activation of immune cells, such as lymphocytes, which produce antibodies to target and neutralize the invaders. The immune response is a complex process that includes various mechanisms, such as the production of memory cells for long-term protection. While skin and mucous membranes are important physical barriers against pathogens, they are not specific to the adaptive defense system. Inflammatory response, on the other hand, is a general defense mechanism that can be triggered by various factors, including infections, injuries, or allergies.

IgE is involved in allergies because it is responsible for triggering an immune response to allergens. When a person with allergies is exposed to an allergen, IgE antibodies bind to mast cells and basophils in the body. This binding causes the release of inflammatory substances such as histamine, which leads to the symptoms of an allergic reaction, such as itching, swelling, and inflammation. IgE is specifically designed to target and respond to allergens, making it the key antibody involved in allergic reactions.

Cytotoxic cells are the only T cells that can directly attack and kill other cells. These cells are a type of white blood cell that play a crucial role in the immune response by identifying and destroying infected or abnormal cells in the body. Unlike regulatory cells, helper cells, and plasma cells, cytotoxic cells possess the ability to directly eliminate target cells through the release of toxic substances or by inducing apoptosis.

The statement is true because the mechanism of the "lethal hit" of cytotoxic T cells does involve a protein called perforin. Perforin is released by cytotoxic T cells and forms pores in the target cell's membrane, allowing entry of enzymes called granzymes. These granzymes then induce cell death by activating caspases, leading to apoptosis of the target cell. Therefore, perforin plays a crucial role in the cytotoxic activity of T cells.

Atopy refers to the genetic predisposition to develop allergies to environmental antigens. It is characterized by an exaggerated immune response, specifically type I hypersensitivity reactions, which cause immediate allergic reactions. These reactions can range from mild symptoms like itching and sneezing to severe symptoms like anaphylaxis. The statement correctly states that atopy is an inherited tendency, implying that individuals with a family history of allergies are more likely to develop allergic reactions to certain environmental triggers. Therefore, the correct answer is True.

Somatic recombination is a process that occurs in B cells, where segments of DNA encoding antibody genes are rearranged to create a unique antibody gene. This process allows each B cell to produce its own distinct antibody, enabling the immune system to recognize and respond to a wide range of antigens. Therefore, the statement that somatic recombination by B cells allows each B cell to form its own unique antibody genes is true.

Antibodies are composed of heavy and light polypeptide chains. These chains are produced by B cells in response to the presence of antigens. The heavy and light chains come together to form the Y-shaped structure of an antibody molecule. The heavy chain determines the class or isotype of the antibody, while the light chain is responsible for antigen recognition and binding. This characteristic composition of antibodies allows them to specifically recognize and bind to antigens, initiating immune responses to eliminate foreign substances from the body.

The statement is true because a transfusion reaction is indeed an acute hypersensitivity to foreign red blood cells. When a person receives a blood transfusion with incompatible blood, their immune system may recognize the foreign red blood cells as a threat and mount an immune response. This can lead to symptoms such as fever, chills, shortness of breath, and in severe cases, organ damage or even death. Therefore, it is important to carefully match blood types and perform compatibility tests before transfusions to prevent such reactions.

Perforins are cytolytic chemicals that are indeed used by NK cells. These chemicals are released by NK cells to create pores in the target cell's membrane, allowing for the entry of toxic enzymes called granzymes. This process ultimately leads to the destruction of the target cell. Therefore, the statement "Perforins are cytolytic chemicals used by NK cells" is true.

Antigens can be complete or incomplete, meaning they can either have all the necessary components to induce an immune response or lack some of these components. This statement is true because antigens can vary in their structure and composition, and not all antigens possess all the necessary features to stimulate an immune response. Incomplete antigens may still be recognized by the immune system, but they may not elicit a full immune response.

The respiratory burst is a process in which macrophages generate reactive oxygen species (ROS) to destroy pathogens. These ROS include free radicals such as superoxide anion (O2-) and hydrogen peroxide (H2O2). Therefore, it is true that the respiratory burst produced by some macrophages releases free radicals.

The statement suggests that tolerance for self-antigens is abnormal, but the correct answer is False. This means that tolerance for self-antigens is actually normal.

Autoimmune diseases are not more common in men than in women. In fact, autoimmune diseases are generally more prevalent in women compared to men. This may be due to hormonal differences, genetic factors, or other underlying mechanisms. Therefore, the statement "Autoimmune diseases are more common in men than in women" is incorrect.

The correct answer is disulfide. Disulfide bonds are strong covalent bonds that form between two cysteine amino acids in the antibody molecule. These bonds help to stabilize the structure of the antibody and are important for its function in recognizing and binding to specific antigens. Hydrogen bonds, on the other hand, are weaker and play a role in maintaining the overall shape of the antibody. Amino acids are the building blocks of proteins, including antibodies, but they do not directly hold the antibody molecule together. Sodium is not involved in the bonding of antibody molecules.

Some immunocompetent cells are specific to certain pathogens or antigens that may not be encountered during our lifetime. Therefore, these cells may never be activated or called to service in our immune system. This is why the statement is true.

B lymphocytes develop immunocompetence in the bone marrow. This is because the bone marrow is the primary site of B cell development and maturation. B cells, also known as B lymphocytes, are a type of white blood cell that plays a crucial role in the immune response. In the bone marrow, B cells undergo a process called V(D)J recombination, which allows them to generate a diverse repertoire of antigen receptors. Once they have developed immunocompetence, B cells can migrate to other lymphoid organs such as the spleen and lymph nodes to participate in immune responses.

Interferons are small proteins secreted by virus-containing cells. They play a crucial role in the immune response by inhibiting the replication of viruses and regulating the immune system. Interferons are produced and released in response to viral infections, and they help to activate other immune cells, such as natural killer cells and macrophages, to fight against the virus. Therefore, interferons are the correct answer as they are directly related to the secretion of small proteins by virus-containing cells.

Passive immunity refers to the transfer of ready-made antibodies to an individual, providing immediate but temporary protection against a specific pathogen. The passage of IgG antibodies from the pregnant mother to her fetus is an example of passive immunity. During pregnancy, the mother's antibodies cross the placenta and provide the fetus with temporary protection against various diseases. This transfer of antibodies helps to ensure that the newborn is initially protected until their own immune system develops fully.

The redness and heat of an inflamed area are caused by local hyperemia, which refers to an increased blood flow to the area. This increased blood flow is a result of vasodilation, the widening of blood vessels. Vasodilation allows more blood to flow into the area, leading to redness and heat.

The second line of defense in the immune response is the inflammatory response. This is a non-specific defense mechanism that occurs when tissues are injured or infected. It involves the release of chemical signals that attract immune cells to the site of infection or injury, causing redness, swelling, and heat. The inflammatory response helps to contain and eliminate pathogens, and also promotes tissue repair. Skin and mucous membranes are part of the first line of defense, which acts as a physical barrier against pathogens. However, they are not specifically part of the second line of defense, which is why the correct answer is the inflammatory response.

IgA is the correct answer because it is primarily found in mucosal areas such as the respiratory, gastrointestinal, and genitourinary tracts. It plays a crucial role in protecting these mucosal surfaces by preventing the attachment and entry of pathogens. IgA antibodies can neutralize viruses and bacteria, block their adhesion to epithelial cells, and promote their elimination through mechanisms like mucociliary clearance. This helps to prevent infections and maintain the integrity of the mucosal barriers.

Haptens are small molecules that bind with self-proteins to produce antigenic substances. They are not antibodies, ions, or reagins. Haptens are typically too small to elicit an immune response on their own, but when they bind to larger proteins, they can become antigens and trigger an immune response.

Our genes play a crucial role in determining the specific foreign substances that our immune system can identify and defend against. This is because our genes contain the instructions for producing proteins, including the receptors on immune cells that recognize antigens. Antigens are foreign substances that can trigger an immune response. Therefore, it is our genes, not antigens, that determine the range of substances our immune system can recognize and resist.

Chemotaxis is the process by which neutrophils and other white blood cells are attracted to an inflammatory site. During inflammation, damaged cells release chemical signals called chemotactic factors, which act as a gradient guiding the white blood cells towards the site of injury. This directional movement allows the immune cells to reach the site of inflammation and initiate the immune response, aiding in the clearance of pathogens and the promotion of tissue repair.

The innate defense system consists of various mechanisms that provide immediate protection against pathogens. One of these mechanisms is the inflammatory response, which is triggered by tissue damage or infection. It involves the release of chemical mediators that cause blood vessels to dilate and become more permeable, allowing immune cells and molecules to enter the affected area. This response helps to contain and eliminate the pathogens. Additionally, the skin and mucous membranes serve as physical barriers that prevent the entry of pathogens into the body. They contain antimicrobial substances and normal flora that further contribute to the innate defense system. Therefore, the correct answer is the inflammatory response and skin and mucous membranes.

Helper T cells play a crucial role in stimulating the proliferation of other lymphocytes. They are responsible for activating and coordinating the immune response by releasing cytokines and interacting with other immune cells. Helper T cells recognize antigens presented by antigen-presenting cells (APCs) such as macrophages and stimulate the proliferation of B cells and cytotoxic T cells, leading to an effective immune response against pathogens. Thus, helper T cells are essential for the activation and expansion of other lymphocytes, making them the correct answer in this context.

The statement implies that fever is not beneficial because it speeds up the cellular metabolic rate and prevents antigen-antibody reactions. However, this is incorrect. Fever is actually a beneficial response by the body to fight off infections. It activates the immune system, increases the production of white blood cells, and enhances the effectiveness of antigen-antibody reactions. Therefore, the correct answer is False.

IgD is a B cell receptor that is found on the surface of mature B cells along with IgM. It plays a role in the activation and differentiation of B cells. IgD is involved in the recognition and binding of antigens, which triggers an immune response. It is also involved in the regulation of B cell development and antibody production. IgD is less abundant than IgM but still plays a crucial role in the immune response.

An allograft refers to a transplant or graft between individuals of the same species but with different genetic makeup. In the given statement, a graft from a monkey to a human would be an example of a xenograft, as it involves transplantation between different species. Therefore, the correct answer is False.

IgG is the main antibody of both primary and secondary immune responses. IgG is the most abundant antibody in the bloodstream and it is able to cross the placenta, providing passive immunity to the fetus. It plays a crucial role in neutralizing toxins, opsonizing pathogens for phagocytosis, and activating the complement system. IgG is also responsible for long-term immunity as it can persist in the bloodstream for an extended period of time, providing protection against future infections.

During fetal development, lymphocytes that do not react to self-antigens are not destroyed. Instead, they undergo a process called positive selection, where only lymphocytes that can recognize self-antigens are allowed to mature. This helps ensure that the immune system can recognize and respond to foreign antigens while avoiding self-reactivity. Therefore, the correct answer is False.

Neutrophils are a type of phagocytic cell that play a crucial role in the immune response. When they encounter large quantities of a foreign substance, such as bacteria, neutrophils can undergo a process called phagocytosis to engulf and destroy the invaders. However, this process can lead to the release of toxic substances and enzymes, which can cause damage to the surrounding tissues and even result in the destruction of the neutrophils themselves. This self-destruction is known as neutrophil extracellular trap (NET) formation and is an important mechanism for eliminating pathogens, but it can also contribute to tissue damage in certain conditions.

The inflammatory response is a protective mechanism of the body that occurs in response to tissue injury or infection. It involves several functions such as preventing the spread of the injurious agent to nearby tissue, disposing of cellular debris and pathogens, and setting the stage for repair processes. However, replacing injured tissues with connective tissue is not a function of the inflammatory response. This process is typically carried out by the process of tissue regeneration or fibrosis, which occurs after the inflammatory response has subsided.

Macrophage APCs, or antigen-presenting cells, are responsible for presenting antigens to T cells. They capture antigens, process them, and present them on their surface along with major histocompatibility complex molecules. This presentation activates T cells, leading to an immune response. Therefore, macrophage APCs play a crucial role in presenting the double activation signal to T cells. Regulatory T cells, helper T cells, complement, and interferon do not directly present antigens to T cells and do not fulfill this role.

Monoclonal antibodies are produced from a single clone of cells and are highly specific for a single antigenic determinant. This means that they bind to a specific site on a single antigen molecule. They are designed to target and bind to a specific antigen, making them highly specific tools in various diagnostic and therapeutic applications. Therefore, the statement that monoclonal antibodies can be specific for several antigenic determinants is false.

Complement fixation is the correct answer because it is a chief antibody-mediated mechanism used against cellular antigens, such as bacteria. Complement fixation involves the activation of the complement system by antibodies, leading to the recruitment of immune cells and the destruction of the target cells. This mechanism plays a crucial role in eliminating pathogens and promoting an effective immune response.

The complement system is a major innate mechanism that mediates the destruction of foreign substances in the body. Complement proteins can directly kill pathogens, enhance phagocytosis by opsonization, and trigger inflammation. They form a cascade of reactions that leads to the formation of membrane attack complexes, causing lysis of target cells. This system plays a crucial role in the immune response against bacteria, viruses, and other pathogens, as well as in the clearance of immune complexes and damaged cells.

In clonal selection of B cells, the substance responsible for determining which cells will eventually become cloned is the antigen. Antigens are molecules that can bind to specific receptors on B cells, triggering their activation and proliferation. This process allows B cells to recognize and respond to specific pathogens or foreign substances in the body. By selecting and cloning B cells that can bind to the antigen, the immune system can mount a targeted and effective immune response.