MCAT Biology › 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?
Macrophages
Cytotoxic T cells
Plasma cells
Natural killer cells
Germinal center B cells
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.
The common precursor for all blood and immune cells, including red blood cells and lymphocytes, is found in what part of the body?
Bone marrow
Liver
Kidney
Spleen
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.
Which of the following group of cells are of the myeloid lineage?
Some dendritic cells
B cells
T cells
NK cells
All of the above
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.
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?
Peripheral tolerance
Central tolerance
Affinity maturation
Clonal deletion
Clonal expansion
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.
Which of the following is not a true statement regarding germinal centers?
T cells are not critical for the formation and maintenance of the germinal center reaction.
They are transient microenvironments that ultimately produce long-lived plasma cells and memory B cells against a specific antigen.
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.
Germinal centers normally form in secondary lymph nodes but can form ectopic ones in other organs including the kidneys and liver.
T cells, especially CD4+ follicular helper T cells, are absolutely critical and necessary for the induction and maintenance of germinal centers.
Which cytokine is typically associated with the T helper 1 (Th1) response?
IFN-gamma
IL-17
IL-4
IL-9
TGF-beta
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
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 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 unable to reconstitute, proliferate, and mature in the recipient mouse.
The donor T cells are inherently defective in their ability to produce cytokines and growth factors needed in the bone marrow reconstitution.
All of these
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.
What is the group of diseases called when a person's immune system loses its ability to recognize its own MHC proteins?
Autoimmune
Hypersensitivity
Allergies
X-linked lymphoproliferative disease
X-linked autosomal recessive diseases
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.
Which of the following class of immunoglobulins is normally responsible for the promotion of the allergy response?
IgE
IgA
IgM
IgD
IgG
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).
Which of the following cell types is considered to be part of the innate immune response?
NK cells
B cells
T cells
Memory cells
Myocytes
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.