Tolerance and Autoimmunity Flashcards
Tolerance
Needed because random generation of diversity is dangerous
Unresponsiveness to an antigen induced by previous experience to that antigen
Self-tolerance
Can distinguish self from non-self
Mechs that contribute to self tolerance
Neg B cell selection in BM Neg T cell selection in Thymus Exlusion of lymphos from tissues Induction of anergy in some cells that reach periphery Tregs
Central tolerance in the bone marrow
No self reaction - Mature B cell
Multivalent self molecule on a cell - Receptor editing/apoptosis
Soluble self molecule - Anergic B cell
Low-affinity, non-cross linking self - mature but clonally ignorant B cell
Peripheral tolerance in the spleen
Multivalent self molecule - apoptosis
Soluble self molecule - anergic B cell that undergoes apoptosis
Low-afinity, non-cross linking self molecule - Mature, clonlally ignorant B cell
No reaction - mature B cell
Affinity model of T cell selection
Positive selection to make sure that they can recognize self MHC molecules
Negative selection - if they recognize self antigens, they die
If TCR is low then
Cells undergo apoptosis because can’t bind to the MHC molecule to undergo positive sleection
Central T cell tolerance
3 way - recognition of self antigen on cortical OR medullary epithelial cell
Recgonition of self antigen on thymic bone marrow derived cell (dendritic cells, macrophages)…these cells die
How are self antigens presented in the thymus?
AIRE controls expression of a lot of these proteins
APECED
Defective AIRE gene…destruction of endocrine tissues including pancreatic islets and susceptibility to fungal infections like Candida
Immunologically privileged sites
Brain, eye, testis, uterus
Regulatory tolerance
T cell specific for self antigen in the thymus becomes a Treg
T cell specific for self or commenssal microbiota antigen in periphery in presence of TGFbeta becomes Treg
IL-10 and TGFbeta from Tres inhibit other self-reactive T cells
Lymphoproliferative dz can be from
Absence of Tregs
Autoimmunity is combination of
Infection/environmental exposre and genetic factors
Graves dz mech and consequence
Antibody against cell surface or matrix antigen (type 2)
Autoantibodies against TSHR
Hyperthyroidism
SLE mech and consequence
Immune complex dz
Autoantibodies and autoreactive T cells to nuclear contents
Glomerulonphritis, vasculitis, rash
HLA associated risk factor for Graves
DR3 - not everyone will have it but 4X as likely to have graves
Men or women more likely for autoimmune?
Women
Graves symptoms
Heat intolerance Nervousness Irratability Warm and moist skin Weight loss with increased appetite Enlarged thyroid Optho problems
Genetics of Graves
Polymorphim in TSHR gene can result in decreased thymic expression (lose central tolerance)
Mutation in Foxp3 and CD25 associated with Tregs
CTLA4 mutation
CD40 mutation changes translation efficiency
HLA-DR3 increased ability to present thyroglobulin antigens
BAFF and APRIL
SLE symptoms
Joint/muscle pain Fever Red rash Chest pain Hair loss Puprle or pale fingers/toes Sensitivity to sun Edema in legs/eyes Oral ulcers Swollen glands Fatigue
Genetic and environmental for SLE
Anti-DNA antibodies
C1q, C4, C2 changes mean can’t clear immune complex
Sunlight, smoking, alcohol, female
HLA DR3, DR2, and DR5
Abberant DNA methylation (like Foxp3)
BCR signaling genes
IRF5 expressed increases cytokines that impair B cell selection and modulate differentiation
Giant cell arteritis
Vasculitis of arteries combined with polymylagia rheumatica
Granuloma formation in the mural layers of inflamed arteries (macrophages form and fuse urrounded by CD4 cells)
Clinical features of giant cell arteritis
Fever of unknown origin HEadache Scalp and temporal artery tenderness Jaw muscle ischemia Vision impairment can include blindness Aortic anyeurysm
