MCAT Biology : Other Immunity Principles

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

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Example Question #1 : Other Immunity Principles

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:

Liver

Spleen

Kidney

Bone marrow

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 #3 : Animal Biology

Which types of leukocytes are granular?

Possible Answers:

Basophils, eosinophils, neutrophils

Neutrophils, basophils, lymphocytes

Lymphocytes, basophils, eosinophils

Basophils, lymphocytes, monocytes

Monocytes, neutrophils, eosinophils

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 #2 : Other Immunity Principles

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

Possible Answers:

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

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 are sites where peripheral tolerance occurs.

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

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

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 #3 : Other Immunity Principles

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

Possible Answers:

IgM

IgD

IgG

IgA

IgE

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 #12 : Animal Biology

Which is not a function of B cells?

Possible Answers:

Ability to form memory cells

Presentation of antigen to T cells

Secretion of extracellular traps

Cytokine and chemokine production

Antibody 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 #4 : Other Immunity Principles

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

Possible Answers:

TGF-beta

IL-17

IFN-gamma

IL-4

IL-9

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 #5 : Other Immunity Principles

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

Possible Answers:

X-linked lymphoproliferative disease

Allergies

X-linked autosomal recessive diseases

Hypersensitivity

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 #5 : Other Immunity Principles

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

Possible Answers:

Myocytes

NK cells

B cells

Memory cells

T cells

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. 

Example Question #6 : Other Immunity Principles

Which of the following group of cells are of the myeloid lineage?

Possible Answers:

Some dendritic cells

B cells

NK cells

T cells

All of the above

Correct answer:

Some dendritic cells

Explanation:

Cells of myeloid lineage include dendritic cells, monocytes, macrophages, neutrophils, basophils, and eosinophils, while cells of lymphoid lineage include NK cells, B cells and T cells.

Example Question #7 : Other Immunity Principles

Which of the following statements is true?

Possible Answers:

In the prevention of autoimmunity, T cell tolerance is more critical than B cell tolerance against self-nuclear antigens.

Naive B cells need more than one signal to become activated towards a specific antigen.

Healthy individuals do not have any B cells that are reactive against self-antigen.

Female sex hormones do not play an important role in the pathogenesis of autoimmune disease.

The elimination of autoreactive lymphocytes during central tolerance is more important in the prevention of autoimmunity than peripheral tolerance.

Correct answer:

Naive B cells need more than one signal to become activated towards a specific antigen.

Explanation:

Naive B cells (and most other immune cell subtypes) need more than one signal to become activated. They normally need B cell receptor signaling (signal 1), costimulation by other receptors (signal 2), and cytokines/chemokines (signal 3). This system is necessary in order to prevent aberrant activation of lymphocytes (safeguard against autoimmunity).  

In regards to the other statements, there are numerous autoreactive B cells at any given time due to the stochastic nature of VDJ recombination and germinal center reactions. Therefore, tolerance mechanisms and checkpoints are incredibly important to keep these cells in check; central and peripheral tolerance are equally important. Self-nuclear reactive B cells and T cells are both necessary and critical in autoimmune pathogenesis. Female sex hormones are definitely believed to contribute greatly to autoimmune disease pathogenesis (e.g. estrogen). Over 75% of autoimmune patients are women.

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