Block 2 Immunology Quiz Questions

Mucous membranes act as an important anatomical barrier to infection by microorganisms. They line various parts of the body such as the respiratory, digestive, and reproductive tracts. These membranes are covered with a layer of mucus that helps to trap and remove pathogens before they can enter the body. Additionally, mucous membranes contain specialized cells that produce antimicrobial substances and immune cells that can help to fight off infections. Therefore, mucous membranes play a crucial role in preventing the entry and spread of microorganisms in the body.

The specific part of an antigen that combines with a specific antibody or T cell receptor is called the epitope. Epitopes are unique regions on the surface of antigens that are recognized and bound by antibodies or T cell receptors. This binding is crucial for the immune response as it helps in the identification and neutralization of foreign substances in the body.

Phagocytosis, endocytosis, and inflammation are all examples of innate immunity. Innate immunity is the first line of defense against pathogens and is present from birth. These processes are part of the body's natural response to infection or injury and do not require prior exposure to the specific pathogen. In contrast, acquired specific immunity refers to the immune response that develops after exposure to a specific pathogen, while the anamnestic response is a term used in reference to the memory response of the immune system.

The complement system is a group of serum proteins that participate in an enzymatic cascade leading to cell lysis. This system plays a crucial role in the immune response by helping to destroy pathogens and infected cells. When activated, the complement system forms a membrane attack complex that inserts into the cell membrane, causing cell lysis and destruction. Therefore, the complement system is the correct answer as it directly relates to the process of cell lysis.

An opsonin is a substance that enhances phagocytosis, which is the process by which cells engulf and digest foreign particles or microorganisms. Opsonins coat the surface of these particles, making them more recognizable and easier for phagocytes to engulf and destroy. This process is an important part of the immune response and helps to eliminate pathogens from the body.

The thymus is considered a primary lymphoid organ because it is the site where T cells, a type of white blood cell involved in immune response, mature and differentiate. Primary lymphoid organs are responsible for the production and maturation of lymphocytes, while secondary lymphoid organs are involved in the activation of lymphocytes and immune response. The thymus plays a crucial role in the development of the immune system, particularly in the early stages of life.

The specific portion of an antigen that is recognized by an antibody or TcR is termed the epitope. An epitope is a small, specific region on the antigen's surface that binds to the antibody or TcR, triggering an immune response. The recognition of the epitope by the immune system is crucial for the immune response to occur and for the body to effectively defend against pathogens. The other options, agretope, MHC, and CD, are not directly related to the specific portion of an antigen recognized by an antibody or TcR.

Lysozyme is a hydrolytic enzyme that is found in mucous secretions. It has the ability to degrade the peptidoglycan cell wall of gram + bacteria. This means that lysozyme can break down the protective outer layer of these bacteria, leading to their destruction. This enzyme plays an important role in the body's defense against bacterial infections, as it helps to prevent the growth and spread of gram + bacteria.

CD8 is a glycoprotein that is primarily found on cytotoxic T cells. It plays a crucial role in the immune response by binding to major histocompatibility complex (MHC) class I molecules on target cells, facilitating the recognition and destruction of these cells. CD8 is not found on all lymphocytes, B cells, or helper T cells, making cytotoxic T cells the correct answer.

TcRs (T cell receptors) are present in the cell membrane of all mature T lymphocytes. T lymphocytes, also known as T cells, are a type of white blood cell that plays a crucial role in the immune response. TcRs are responsible for recognizing specific antigens presented by antigen-presenting cells and initiating an immune response. Therefore, all mature T lymphocytes possess TcRs on their cell membrane to enable them to identify and respond to foreign antigens.

Phagocytosis is the process by which a cell engulfs and internalizes solid particles, such as bacteria or debris. This process involves the formation of pseudopods that surround the particle and eventually fuse together, enclosing it within a membrane-bound vesicle called a phagosome. The phagosome then fuses with lysosomes, leading to the degradation of the engulfed material. This term is commonly used to describe the uptake of particulate material by immune cells, such as macrophages and neutrophils.

Interferons are proteins produced by virally infected cells as part of the immune response. They play a crucial role in inhibiting viral replication and spreading to other cells. Interferons activate the immune system and stimulate the production of other anti-viral proteins, helping to limit the spread of the infection. Therefore, interferons are the correct answer as they are specifically produced by virally infected cells.

Monocytes are a type of white blood cell that circulate in the blood. When they enter the tissues, they undergo a process called differentiation and transform into macrophages. Macrophages are large immune cells that play a crucial role in engulfing and destroying pathogens, dead cells, and other foreign substances in the body. They are also involved in initiating and regulating immune responses. Therefore, the correct answer is macrophages.

T cell receptors are not an example of an innate immune mechanism because they are part of the adaptive immune system. Innate immune mechanisms are the body's first line of defense and are present from birth, whereas adaptive immune responses are specific to particular pathogens and develop over time. T cell receptors are involved in recognizing specific antigens and triggering an adaptive immune response, making them distinct from the innate immune mechanisms listed in the other options.

Plasma cells are a type of antibody-secreting cells. They are derived from B lymphocytes and are responsible for producing and secreting large amounts of antibodies into the bloodstream. These antibodies play a crucial role in the immune response by recognizing and neutralizing foreign pathogens. T cell blasts are immature T cells, macrophages are phagocytic immune cells, and B lymphoblasts are activated B cells that have not yet differentiated into plasma cells.

The thymus would not be considered a secondary lymphoid organ because it is primarily involved in the development and maturation of T cells, which are a type of white blood cell involved in immune responses. Secondary lymphoid organs, on the other hand, are responsible for the initiation of immune responses and include lymph nodes, spleen, and tonsils.

Class II MHC proteins are produced only by antigen presenting cells. These cells, such as macrophages, dendritic cells, and B cells, play a crucial role in presenting antigens to T cells. Class II MHC proteins bind to antigens that have been internalized by the antigen presenting cells and present them on the cell surface to activate T cells. In contrast, Class I MHC proteins are present on the surface of all nucleated cells and present antigens derived from intracellular pathogens. Class III MHC proteins are involved in the complement system and inflammatory responses, but they are not specific to antigen presentation.

T lymphocytes undergo the process of negative selection in the thymus. This is because the thymus is a primary lymphoid organ where T cells mature and develop their antigen receptors. During negative selection, T cells that recognize self-antigens too strongly are eliminated to prevent autoimmunity. The thymus provides a controlled environment for this process to occur, ensuring that only T cells with appropriate antigen recognition are allowed to enter the circulation.

Neutrophils are the most abundant type of white blood cell in the blood of normal humans. They play a crucial role in the immune system by engulfing and destroying bacteria and other foreign substances. Neutrophils are highly mobile and are among the first cells to arrive at the site of infection or inflammation. They are characterized by their multi-lobed nucleus and granular cytoplasm.

B cells undergo a process of negative selection in the bone marrow. This is where immature B cells are screened for self-reactivity and those that recognize self-antigens too strongly are eliminated. This process helps to ensure that only B cells that can effectively recognize foreign antigens are allowed to mature and participate in the immune response. The spleen, thymus, and lymph nodes also play important roles in the immune system, but negative selection of B cells specifically occurs in the bone marrow.

lecture only mentions Macrophages but internet search reveals that all of the above is correct

Fibrin is produced during the clotting cascade. The clotting cascade is a series of reactions that occur in response to injury to form a blood clot. Fibrin is a protein that plays a crucial role in the formation of blood clots. It is formed from fibrinogen, which is activated by thrombin, an enzyme in the clotting cascade. Fibrin forms a mesh-like structure that helps to stabilize the blood clot and prevent excessive bleeding. Therefore, the production of fibrin is an important step in the clotting cascade.

The correct answer is bone marrow. The bone marrow is the primary site where myeloid cells differentiate from committed progenitors to mature cells. It is responsible for the production of red blood cells, platelets, and most white blood cells, including myeloid cells. The bone marrow contains the necessary microenvironment and stromal cells that support the differentiation and maturation of myeloid cells. The thymus is primarily involved in the maturation of T lymphocytes, while the spleen and lymph nodes play a role in immune responses but are not the primary sites for myeloid cell differentiation.

Kinins are not classified as cytokines because they are a group of small proteins that are involved in inflammation and blood vessel dilation, but they do not have the same signaling functions as cytokines. Cytokines are a broad category of proteins that are involved in cell signaling and communication, regulating immune responses and inflammation. Interleukins, tumor necrosis factors, and interferons are all examples of cytokines.

Neutrophils do not function as antigen-presenting cells (APCs). APCs are responsible for processing and presenting antigens to activate T cells in the immune response. B lymphocytes, macrophages, and interdigitating dendritic cells are all examples of APCs. Neutrophils, on the other hand, primarily function as phagocytes and are involved in the innate immune response by engulfing and destroying pathogens. They do not have the ability to present antigens to T cells.

C-reactive protein is classified as an acute-phase protein because it is produced by the liver in response to inflammation or infection. Acute-phase proteins are involved in the body's immune response and their levels increase during acute inflammation. C-reactive protein levels can be used as an indicator of inflammation in various conditions such as infections, autoimmune diseases, and cardiovascular diseases.

Prostaglandins and leukotrienes are classified as lipid inflammatory mediators because they are lipid molecules that are involved in the inflammatory response. They are produced by various cells in the body, including immune cells, and play a role in regulating inflammation and immune responses. These molecules are involved in the dilation and constriction of blood vessels, the recruitment of immune cells to sites of inflammation, and the production of pain and fever. Therefore, they are considered important mediators of inflammation.

The correct answer is "calor - heat." In medical terminology, calor refers to the symptom of heat or warmth in a specific area of the body. This is often associated with inflammation or infection. The other options mentioned, such as dolor, rubor, and tumor, are also medical terms, but they are not correctly matched with their corresponding definitions in this question.

In an inflammatory response, the first physiological event that occurs is vasodilation of the capillary network leading to the site of injury or infection. This is because vasodilation increases blood flow to the affected area, which helps to deliver immune cells and nutrients necessary for the inflammatory response. Increased blood flow also leads to redness and warmth at the site of injury or infection.

Cysteine-rich cationic peptides that circularize and form ion-permeable channels in bacterial and mammalian cell membranes are known as defensins. Defensins are a type of antimicrobial peptide that play a crucial role in the innate immune response by killing and neutralizing invading pathogens. They are produced by various cells in the body, including neutrophils, macrophages, and epithelial cells, and are highly effective against a wide range of microorganisms. Defensins work by disrupting the integrity of bacterial and mammalian cell membranes, leading to cell death.

The Bursa of Fabricius is an organ found in birds that plays a crucial role in their immune system development. In humans, there is no direct equivalent organ to the Bursa of Fabricius. However, the bone marrow is responsible for the production of immune cells, including B cells, which are also produced in the Bursa of Fabricius. Therefore, the bone marrow can be considered as the functional equivalent to the Bursa of Fabricius in humans.

Null cells refer to a category of lymphocytes that do not express markers for T cells or B cells. They are considered a part of the lymphocyte lineage because they originate from the same precursor cells as T cells and B cells. Null cells are also known as natural killer (NK) cells, which play a vital role in the innate immune response by recognizing and killing infected or cancerous cells. They are characterized by their ability to directly kill target cells without prior sensitization or activation.

Histamine is known to stimulate pain receptors in the skin during an inflammatory response. When released by mast cells during an immune response, histamine causes blood vessels to dilate, leading to increased blood flow to the affected area. This dilation and increased blood flow can activate pain receptors in the skin, resulting in pain and discomfort.

Superoxide anion (O2-) is a reactive oxygen species that can undergo dismutation to form hydrogen peroxide (H2O2). It can also react with other molecules to generate hydroxyl radicals (OH'), which are highly reactive and can cause damage to cellular components. Singlet oxygen is another reactive oxygen species that can be formed through the reaction of superoxide anion with molecular oxygen. However, superoxide anion does not directly lead to the formation of nitric oxide (NO), making it the correct answer. Nitric oxide is produced by the enzyme nitric oxide synthase in a separate pathway.

T cells that survive the process of negative selection are those that recognize self MHC molecules but are specific for foreign antigens. Negative selection is a process in the thymus where T cells that recognize self antigens too strongly are eliminated to prevent autoimmunity. T cells that recognize foreign antigens are necessary for immune responses against pathogens, so they are allowed to survive. In this case, the T cells that recognize self MHC + foreign antigen would survive because they are specific for foreign antigens while still recognizing self MHC molecules.

The paracortex is considered to be "T cell rich" in the lymph node. This is because it contains a high concentration of T cells, which are important for cell-mediated immune responses. The paracortex also contains high endothelial venules (HEVs), which allow T cells to enter the lymph node from the bloodstream. This area is crucial for the activation and proliferation of T cells, making it an important region for immune responses. The other options, primary follicles, medulla, and germinal centers, do not have as high a concentration of T cells as the paracortex.

Lymphocytes are not in the myeloid pathway of cellular differentiation. The myeloid pathway refers to the differentiation of cells that give rise to various types of white blood cells, including macrophages and basophils. Lymphocytes, on the other hand, are derived from the lymphoid pathway of cellular differentiation. They play a crucial role in the immune response and can be further classified into B cells, T cells, and natural killer cells.

The correct answer is "1-5% of the progenitor T cells which enter the thymus leave as mature T cells." This statement suggests that only a small percentage of progenitor T cells that enter the thymus go on to become mature T cells. This implies that the majority of progenitor T cells undergo processes such as positive and negative selection, differentiation, and maturation within the thymus before becoming mature T cells.

IL-3 is the hematopoietic growth factor that is believed to act at the level of the pluripotent stem cell. IL-3, also known as interleukin-3, is a cytokine that stimulates the production and differentiation of various blood cells. It plays a crucial role in the regulation of hematopoiesis, promoting the growth and development of pluripotent stem cells into different blood cell lineages, including red blood cells, white blood cells, and platelets. IL-3 acts as a survival factor for these stem cells, supporting their proliferation and preventing apoptosis. Therefore, IL-3 is considered to have a direct effect on pluripotent stem cells in the hematopoietic system.

The thymus is a gland located in the chest that plays a crucial role in the development and maturation of T-cells, which are important for immune system function. The thymus is largest at puberty because this is the time when the immune system is actively developing and maturing. As a person reaches puberty, the thymus gland gradually increases in size and reaches its maximum size. After puberty, the thymus begins to shrink and becomes less active, which is why it is at its largest actual size during this stage of life.

Mature T cells are found in the medulla of the thymus. The thymus is divided into two main regions, the cortex and the medulla. The cortex is where T cells undergo maturation and selection, while the medulla is where the mature T cells migrate to. Hassal's corpuscles, which are concentrically arranged epithelial cells, are also found in the medulla of the thymus. Therefore, the correct answer is medulla.

The red pulp of the spleen is primarily populated by erythrocytes and lymphocytes. Erythrocytes, also known as red blood cells, are responsible for carrying oxygen to the body's tissues. Lymphocytes are a type of white blood cell that play a crucial role in the immune response, helping to fight off infections and diseases. Together, erythrocytes and lymphocytes make up the majority of cells in the red pulp of the spleen, contributing to its important functions in oxygenation and immune response.

The T cell region of the spleen is known as the periarteriolar lymphoid sheath. This region is located around the central artery of the white pulp and consists mainly of T cells. It plays a crucial role in the immune response by facilitating the activation and proliferation of T cells. The periarteriolar lymphoid sheath is an important component of the spleen's immune function and helps in the recognition and elimination of pathogens.

The correct answer is Hageman Factor. The kinin cascade, clotting cascade, and fibrinolytic cascade are all activated by Hageman Factor. Hageman Factor is a protein involved in the coagulation system and plays a crucial role in initiating the clotting process. It activates other factors and pathways, leading to the formation of blood clots. Additionally, Hageman Factor is also involved in the kinin cascade, which produces bradykinin, a substance that causes blood vessels to dilate and increase permeability. Therefore, Hageman Factor is responsible for activating multiple cascades in the body.

When macrophages are activated with lipopolysaccharide and IFN-g, they produce high levels of hydrogen peroxide. This is because lipopolysaccharide and IFN-g stimulate the production of reactive oxygen species (ROS) in macrophages, including hydrogen peroxide. ROS, such as hydrogen peroxide, play a crucial role in the immune response by acting as signaling molecules and antimicrobial agents. They help to kill invading pathogens and regulate immune cell functions. Therefore, the activation of macrophages with lipopolysaccharide and IFN-g leads to the production of high levels of hydrogen peroxide.