MCAT Biology : Immune System
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Example Questions
Example Question #23 : Antibodies And Antigens
Which immunoglobulin is the predominant subclass that can cross the placenta?
IgM
IgD
IgE
IgG
IgA
IgG
IgG (exists as a monomer in the blood) and IgE are both small enough to cross the placenta however, IgE is present in very low levels in the plasma.
Example Question #21 : Antibodies And Antigens
Allergies are conditions caused by hypersensitivity by the immune response and typically develop upon first encounter with the foreign antigen. The onset of the allergic response is typically fast and acute. Symptoms include shortness of breath, runny nose, red eyes, swelling, etc. Mast cells are found in skin, mucosal tissue and the gastrointestinal tract and play a significant role in the inflammatory response and in immediate allergic reactions.
Upon exposure to allergen bound by antibody, mast cells are able to release potent inflammatory mediators, such as histamine, proteases, chemotactic factors, and cytokines act on the vasculature, smooth muscle, mucous glands and inflammatory cells. Which antibody subclass is bound to the allergens and responsible for activating mast cells?
IgE
IgA
IgD
IgG
IgM
IgE
IgE is the subclass of immunoglobulins that plays a critical role in the allergy response. IgE binds to allergens which in turn bind to Fc receptors on the mast cells, triggering the release of numerous inflammatory mediators, including histamine.
Example Question #81 : Immune System
In what part of the body do T cells undergo maturation?
Tibia
Bone marrow
Spleen
Thymus
Liver
Thymus
T cells originate from hematopoietic stem cells in the bone marrow and migrate to the thymus where they undergo maturation.
Example Question #453 : Mcat Biological Sciences
The mechanisms of antibody-mediated antigen disposal occur in the what order?
Agglutination, opsonization, neutralization
Neutralization, agglutination, opsonization
Neutralization, opsonization, agglutination
Agglutination, neutralization, opsonization
Opsonization, agglutination, neutralization
Neutralization, agglutination, opsonization
The mechanisms of antibody-mediated antigen disposal occur in the order of neutralization, agglutination, and opsonization. During the process of neutralization, antibodies block pathogenic activity. During agglutination, antibody molecules aggregate multiple pathogens. Finally, during opsonization phagocytes engulf pathogens bound to antibodies.
Example Question #83 : Immune System
Which toll-like receptor (TLR) recognizes single-stranded RNA?
TLR4
TLR3
TLR9
TLR5
TLR7
TLR7
TLR7 recognizes single-stranded RNA while TLR9 recognizes DNA, TLR4 recognizes lipopolysaccharide from gram-negative bacteria, TLR5 recognizes flagellin, and TLR3 recognizes double-stranded RNA.
Example Question #454 : Mcat Biological Sciences
Major histocompatibility complex 1 (MHC-I) presents antigen to which T cell subclass?
Neither CD4+ nor CD8+ T cells
Both CD4+ and CD8+ T cells
CD8+ T cells
CD4+ T cells
A T cell subclass that is not listed in any of the other answer choices
CD8+ T cells
MHC-I on antigen-presenting cells (such as dendritic cells and macrophages) presents antigen to CD8+ T cells. MHC-II presents antigen to CD4+ T cells.
Example Question #455 : Mcat Biological Sciences
Naive T cells need to be initially presented with antigen in order to be activated. Which cell type is involved with this initial presentation?
Neutrophils
Basophils
Dendritic cells
NK cells
Platelets
Dendritic cells
Out of all of the possible choices, only dendritic cells can process and present antigen to T cells. B cells and macrophages are other possible cell types that can be antigen-presenting cells.
Example Question #1 : Immune Proteins And Signals
Toll like receptors (TLR's) are pattern recognition receptors that recognize specific pathogen-associated molecular patterns (PAMP's) on different pathogens and induce an immune response against the foreign pathogen. Numerous immune cell types express TLR's, including antigen-presenting cells and natural killer cells. TLR's play a critical role in the recognition and induction of the immune response against viruses.
A person that has a decreased inherent ability to detect RNA viruses such as influenza and hepatitis would presumably have a defect in which specific TLR?
TLR7
TLR9
TLR2
TLR4
TLR5
TLR7
TLR7 recognizes single-stranded RNA. TLR9 recognizes DNA, TLR4 recognizes lipopolysaccharide, TLR2 recognizes different bacterial components, TLR5 recognizes flagellin.
Example Question #7 : Immune Proteins And Signals
The complement system consists of plasma proteins that can directly or indirectly be activated by foreign pathogens. This leads to the induction of a signaling cascade of reactions that occurs on the surface of the pathogens, which leads to different effector functions including opsonization and neutralization. Deficiencies in different components of complement has been linked to an increased susceptibility to autoimmune diseases, including systemic lupus erythematosus (SLE).
Which of the following would be the most likely scenario regarding how a complement deficiency would result in an increased risk of developing autoimmunity?
Complement deficiency leads to increased killing of regulatory T cells, which allow autoreactive lymphocytes to escape apoptosis.
Complement deficiency leads to a decrease in the formation of antibody-antigen-complement immune complexes, resulting in decreased deposition on tissues.
Complement deficiency leads to increased apoptosis, which leads to a decrease in the presence of self-antigens, thus altering peripheral tolerance.
Complement deficiency leads to decreased binding to self-antigens from apoptotic cells, resulting in an increased amount of self-antigen present, thus increasing the chances of encountering autoreactive lymphocytes.
Complement deficiency leads to an increase in inflammatory monocytes, which leads to a chronic inflammatory state.
Complement deficiency leads to decreased binding to self-antigens from apoptotic cells, resulting in an increased amount of self-antigen present, thus increasing the chances of encountering autoreactive lymphocytes.
The complement system is able to protect against immune responses to autoantigens through the elimination of lymphocytes that are reactive against self antigens. Complement proteins are able to coat self antigens from apoptotic cells and deliver them to developing B cells (through binding to the B cell's complement receptors) and enhancing negative selection. A defective complement system increases the amount of self-antigen present, which can lead to increased chances of binding to autoreactive lymphocytes.
Example Question #81 : Immune System
The common precursor for all blood and immune cells, including red blood cells and lymphocytes, is found in what part of the body?
Spleen
Kidney
Bone marrow
Liver
Bone marrow
All blood cells, including erythrocytes and lymphocytes, come from the same stem cell precursor in the bone marrow. These hematopoietic stem cells give rise to both the myeloid and lymphoid progenitor cells, which are responsible for all blood cells and immune cells. This common precursor spawns cells that then differentiate into the various components of humoral, cell-mediated, and innate immunity.
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