University:
York University
Course:
SC/BIOL 3120 | Immunobiology
Academic year:

2023
Views:

455

Pages:

4
Author:

Niklas

Mechanisms of Tolerance Hypersensitivity vs. Transplantation vs. Autoimmunity Type Mechanism Allergy Hypersensitivity Autoimmunity Type I Immediate Pollen, dust Anaphylaxis Allergic Asthma Type II Cytotoxic Drugs Hemolytic Anemia Autoimmune Hemolytic Anemia Type III Immune Complex Serum Sickness Glomerulonephritis SLE Type IV T-cell mediated Contact dermatitis Delayed-type hypersensitivity MS, RA Tolerance: The capacity of an immune system to prevent the reaction of its cells and antibodies against host components. Self-tolerance vs. non-self tolerance Immunity vs. Tolerance Immunity tends to favor immunity. Tolerance tends to favor community. What influences tolerance? Factors that Promote Tolerance: Persistent low-level stimulation of the immune system Exposure to antigens during fetal and neonatal development Immunosuppressive molecules Clonal deletion Anergy Factors that Impair Tolerance: Persistent high levels of inflammation Disruption of the balance between T helper and T regulatory cells Genetic predisposition Environmental factors How long will it be around? Control and Tolerance Peripheral Tolerance Anergy Clonal deletion Suppression by regulatory T cells Deviation of immune responses Antigen Sequestration: The partitioning of various self-antigens away from immune mediators (immune privilege). Antigen Segregation = Antigen Sequestration Examples: eyes, testis, CNS, or heart Central Tolerance: Deletion of self-reactive lymphocytes in their primary lymphoid organs. T-cell negative selection: Deletion of all clones that bind too tightly (or too weakly) to self-antigen. B-cell negative selection: Deletion of all clones that bind too tightly (or too weakly) to self-antigen. Peripheral Tolerance: Renders self-reactive lymphocytes non-responsive. Actively generates inhibitory cells (usually lymphocytes) outside primary lymphoid organs. Anergy: Signal 1, but no signal 2. Block in activation. Active Suppression by Tregs: Repeated stimulation leads to cell death by mitochondrial (intrinsic) or death receptor (extrinsic) pathways.