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10 Cards in this Set

  • Front
  • Back
What is the general definition of tolerance
State where a potentially reactive cell is made unresponsive by initial contact with antigen so that if a cell encounters antigen a second time, it will not respond to antigen
What is central tolerance
Denotes the mechanisms whereby self-antigens are discriminated from non-self antigens during ontogenetic development (immature cells)
What is peripheral tolerance
Denotes mechanisms by which adult cells fail to respond to self-antigens in the periphery (mature cells)
How is central T cell tolerance induced
Occurs during T cell ontogenetic development. Positive and negative selection occurs in the thymus as T cells recongnize MHC molecules
How is central B cell tolerance induced
Can occur in immature B cells in the bone marrow and the secondary lymphoid tissues. B cells pass through a stage of development in which they are exquisitely susceptible to tolerance induction. B cell contact with antigen during this time makes it tolerant.
What are three mechanisms responsible for B cell tolerance induction
Clonal deletion, Clonal anergy, Receptor editing
What are the two major classification schemes for categorizing autoimmune diseases
1. By organ-specific diseases vs. systemic diseases (Grave's and Systemic lupus erythematosus)
2. By type of immunological effector mechanisms (Type 2,3,or 4 hypersensitivity)
What is an immunologically priviledged site
Any of those locations in the body where immune responses to antigens are not destructive to tissue or are suppressed. Major sites are brain, anterior chamber of the eye, testis, renal tubule, uterus, and possible joint and adrenal glands
What are some potential mechanisms for induction of autoimmunity
Disruption of tissue barrier; Inappropriate expression of MHC class II; Suppression of Regulatory T cell (CD25 CD4); molecular mimicry; superantigens; binding of pathogen to self-protein
What are the effector mechanisms of allograft rejections
Hyperacute rejection (mediated by preformed antibodies); Acute rejection
(mediated by T cells, macrophages, and antibodies); Chronic rejection (alloantibodies that result from stimulation by the indirect pathway of allorecognition)