MCAT Biology : Immune and Lymphatic Systems
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Example Questions
Example Question #2 : Other Immunity Principles
Which of the following group of cells are of the myeloid lineage?
NK cells
All of the above
B cells
T cells
Some dendritic cells
Some dendritic cells
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 #5 : Other Immunity Principles
Which of the following statements is true?
Healthy individuals do not have any B cells that are reactive against self-antigen.
The elimination of autoreactive lymphocytes during central tolerance is more important in the prevention of autoimmunity than peripheral tolerance.
Naive B cells need more than one signal to become activated towards a specific antigen.
Female sex hormones do not play an important role in the pathogenesis of autoimmune disease.
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.
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.
Example Question #11 : Other Immunity Principles
Somatic hypermutation of B cell receptor (BCR) genes in immature, developing B lymphocytes generates numerous specificities that are useful against a specific foreign antigen, however the process generates many more specificities that are either low affinity or reactive against self-antigens. Tolerance mechanisms, which include apoptosis or anergy, are in place in the bone marrow to prevent these "non-useful" or "harmful" B cells from exiting. However, these checkpoints are not 100% accurate and numerous B cells with autoreactive BCR's leave and travel to secondary lymphoid tissues.
Tolerance checkpoints exist in secondary lymphoid tissues to purge the repertoire of low-affinity or autoreactive B cells. What is the tolerance checkpoint mechanism in the secondary lymphoid tissues referred to as?
Central tolerance
Affinity maturation
Clonal deletion
Clonal expansion
Peripheral tolerance
Peripheral tolerance
Peripheral tolerance is the correct term for the tolerance checkpoint mechanisms that are instituted in the secondary lymphoid organs such as spleen and lymph nodes. B cells with BCR specificities that are low affinity or reactive against self-nuclear antigen will be purged from the repertoire.
Example Question #12 : Other Immunity Principles
Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by the loss of tolerance to self antigens leading to the presence of high autoantibody titers. There are several underlying causes behind SLE, one of which is a dysregulation in the clearance of apoptotic cells, which can lead to secondary necrosis. This leads to the leakage of danger signals which contributes to the loss of peripheral tolerance and chronic inflammation.
A deficiency in the clearance of apoptotic cells can be attributed to which immune cell type?
Natural killer cells
Germinal center B cells
Macrophages
Cytotoxic T cells
Plasma cells
Macrophages
The defect in clearance of apoptotic cells in SLE is mainly attributed to macrophages, which serve integral roles in phagocytosis of dead cells and debris. An inability to clear these apoptotic cells over time leads to secondary necrosis, which results in the production and release of several DAMPS or damage-associated molecular pattern molecules which are potent inducers of the immune response.
Example Question #123 : Immune And Lymphatic Systems
Bone marrow chimeric mice are an invaluable tool used by immunologists to elucidate specific mechanisms of the immune response. The generation of these chimeras involve whole body irradiation to eliminate the mouse bone marrow followed by adoptive transfer of bone marrow from a donor mouse (usually transgenic).
One critical step in the successful generation of bone marrow chimeric mice involves the depletion of T cells from the donor bone marrow. Which of the following is reason for this necessary step?
The donor T cells are unable to reconstitute, proliferate, and mature in the recipient mouse.
All of these
The donor T cells may be activated by the MHC antigens from the recipient's cells, resulting in a graft versus host response.
The donor T cells have an inherently reduced cytotoxic killing ability.
The donor T cells are inherently defective in their ability to produce cytokines and growth factors needed in the bone marrow reconstitution.
The donor T cells may be activated by the MHC antigens from the recipient's cells, resulting in a graft versus host response.
T cells from the donor must be depleted due to the risk of incompatible MHC antigens on the recipient cells. If there is incompatibility, the donor T cells will attack and kill the host cells resulting in a graft versus host response.
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