Flashcards in Regulation of the Immune Response Deck (13):
What is immunological tolerance?
tolerance is the lack of response to a specific antigen
Immunological tolerance involves
elimination of cell populations reactive to that antigen, neutralization of reactive cell populations, generation of unique cell populations that can produce antigen specific tolerance
mechanisms of tolerance induction
deletion of reactive cells, inactivation of reactive cells (anergy)
immature or developing T cells are deleted. programmed cell death or apoptosis. eliminates autoreactive T cells in the thymus. result of tight association of the autoreactive TCR to MHC presented antigen on specialized thymic dendritic cells
immature cells, exposed to antigen in association with appropriate MHC can be functionally eliminated, especially if these cells do not receive appropriate co-stimulatory signal.
delete antigen specific helper cells and therefore lose CD8+ T cell cytotoxicity or B cell antibody formation that requires help
Generation of suppressor or regulatory T cells
active process involving antigen/MHC specific cells
Blocking of presentation or activation
directed at co-receptors (CD4 or CD8) or at MHC molecules so as to reduce effective presentation
mechanisms of tolerance in T cells
clonal deletion, clonal anergy, functional deletion, generation of suppressor or regulatory T cells, blocking of presentation or activation
mechanisms of tolerance in B cells
clonal deletion of B cells, clonal abortion/clonal anergy/functional deletion
inducing and maintaining tolerance depends on
maturity of host, immunogenicity of a substance, dose of the substance, form of the substance, immunosuppressive drugs
CD4+ T cells that can control autoreactive CD4+ T cells through the release of cytokines. They must be positively selected in the thymus on peptide loaded MHC class II molecules.