MCAT Biology : MCAT Biological Sciences

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

Example Question #461 : Mcat Biological Sciences

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?

Possible Answers:

TLR5

TLR9

TLR4

TLR2

TLR7

Correct answer:

TLR7

Explanation:

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?

Possible Answers:

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.

Correct answer:

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.

Explanation:

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?

Possible Answers:

Kidney

Bone marrow

Liver

Spleen

Correct answer:

Bone marrow

Explanation:

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.

Example Question #2 : Other Immunity Principles

Which types of leukocytes are granular?

Possible Answers:

Lymphocytes, basophils, eosinophils

Monocytes, neutrophils, eosinophils

Basophils, eosinophils, neutrophils

Basophils, lymphocytes, monocytes

Neutrophils, basophils, lymphocytes

Correct answer:

Basophils, eosinophils, neutrophils

Explanation:

The five types of leukocytes are: neutrophils, lymphocytes, monocytes, eosinophils, and basophils. Three of these (neutrophils, eosinophils, and basophils) contain granules, tiny sacs containing enzymes which can lyse microorganisms. The other two leukocytes (lymphocytes and monocytes) do not contain these granules.

Example Question #1 : Other Immunity Principles

Which of the following is not a true statement regarding germinal centers?

Possible Answers:

They are transient microenvironments that ultimately produce long-lived plasma cells and memory B cells against a specific antigen.

Germinal centers are sites where peripheral tolerance occurs.

B cells that have undergone a germinal center reaction should produce antibody against a specific antigen that is higher affinity than naive B cells.

Germinal centers normally form in secondary lymph nodes but can form ectopic ones in other organs including the kidneys and liver.

T cells are not critical for the formation and maintenance of the germinal center reaction.

Correct answer:

T cells are not critical for the formation and maintenance of the germinal center reaction.

Explanation:

T cells, especially CD4+ follicular helper T cells, are absolutely critical and necessary for the induction and maintenance of germinal centers.  

Example Question #431 : Systems Biology And Tissue Types

Which of the following class of immunoglobulins is normally responsible for the promotion of the allergy response?

Possible Answers:

IgE

IgG

IgA

IgM

IgD

Correct answer:

IgE

Explanation:

IgE plays a critical role in induction and promotion of type I hypersensitivity (allergy, asthma, etc.) normally through engagement of Fc receptors on the surface of basophils and mast cells, which primes them to produce large quantities of granules and chemical mediators (including histamines and cytokines).

Example Question #2 : Understanding Immunological Processes

Which is not a function of B cells?

Possible Answers:

Presentation of antigen to T cells

Antibody production

Secretion of extracellular traps

Ability to form memory cells

Cytokine and chemokine production

Correct answer:

Secretion of extracellular traps

Explanation:

B cells play numerous integral roles in the immune response against foreign pathogens (viruses, bacteria, and fungi), including forming transient microenvironments called germinal centers, where they produce long-lived plasma cells that are high affinity for specific antigen and memory B cells. They also serve as antigen-presenting cells and producers of cytokines and chemokines; However, B cells are not able to produce extracellular traps, which primarily are composed of DNA and work to trap pathogens. Neutrophils produce extracellular traps.

Example Question #114 : Immune And Lymphatic Systems

Which cytokine is typically associated with the T helper 1 (Th1) response?

Possible Answers:

IFN-gamma

IL-17

IL-9

IL-4

TGF-beta

Correct answer:

IFN-gamma

Explanation:

The following helper T cells are paired with the following cytokines:

Th1 - IFN-gamma

Th2 - IL-4

Th9 - IL-9

Th17 - IL-17

Tfh - IL-21

Example Question #432 : Systems Biology And Tissue Types

What is the group of diseases called when a person's immune system loses its ability to recognize its own MHC proteins?

Possible Answers:

Hypersensitivity

Allergies

X-linked lymphoproliferative disease

X-linked autosomal recessive diseases

Autoimmune

Correct answer:

Autoimmune

Explanation:

Autoimmunity arises when one's immune system is unable to recognize its own MHC proteins, which could potentially lead to aberrant activation of the immune response. Furthermore, autoreactive immune cells that are normally induced to undergo apoptosis may be able to escape these tolerance mechanisms and induce tissue damage.

Example Question #444 : Biology

Which of the following cell types is considered to be part of the innate immune response?

Possible Answers:

NK cells

Memory cells

T cells

B cells

Myocytes

Correct answer:

NK cells

Explanation:

Natural killer (NK) cells are prominent members of the initial innate immune response against foreign pathogens. They play numerous integral roles in the innate response including cytotoxic killing, cytokine production, and antibody-mediated cell cytotoxicity. 

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