Term
Role of
Major Histocompatability Complex
(MHC)
in Adaptive immunity
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Definition
- Self and non-self recognition
- Positive and negative selection in the thymus
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Term
Major Histocompatability Complex
(MHC)
Regions |
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Definition
(on chromosone 6)
- Class I: classical (HLA-A,B,C) and non-classical (HLA E, G and F--inhibition and tolerance related ) HLA genes
- Class II: (HLA DP, DQ and DR) expressed on APC
- Class III: complement and inflammatory related genes (C2, C4, TNF, Lymphotoxins)
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Term
Major Histocompatibility Complex
(MHC)
Class I description |
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Definition
- classical (HLA-A,B,C) HLA genes on ALL nucleated cells (not on RBCs) present INTRACELLULAR peptide Ag (ie viruses) to CD8
- non-classical (HLA E, G and F--inhibition and tolerance related ) HLA genes on extravillous and trophoblasts (protects fetus from maternal lympohcytes)
- alpha chain and beta-2 microglobulin
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Term
Major Histocompatibility Complex
(MHC)
Class II description
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Definition
- HLA DP, DQ and DR: expressed on APC
- ie B cells, dendritic cells, thymic epith, macrophages, activated T cells (up reg'd by gIFN
- Processes EXOGENOUS/extracellular proteins to CD4 Tcells
- Intrathymic selection of CD4 Tcells
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Term
Major Histocompatibility Complex
(MHC)
Genetics |
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Definition
- Extensive polymorphisms at all three (class I, II and II) loci, but tight linkage/low frequency of recombination ie inherited as a unit
- Autosomal Co-dominant inheritance (both maternal and papernal alleles are expressed)
- Inherited as a haplotype (single chromosone of gene cluster)
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Term
Major Histocompatibility Complex
(MHC)
Genetics
Potential sibling matching
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Definition
- 25% chance of full match
- 50% chance of half match
- 25% chance of no match
(inherit maternal or paternal haplotype or both)
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Term
Major Histocompatibility Complex
(MHC)
Clinical Relevance
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Definition
- Infectious disease pathogenesis
- Autoimmune disease pathogensis
- Primary Immune deficiency
- Cancer surveillance
- Transplant rejection/GVH
- Risk assessment (HLA predicts risk, natural history and clinical subtypes of many diseases)
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Term
Major Histocompatibility Complex
(MHC)
Linkage disequalibrium
(definition) |
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Definition
- chance that genesat different loci inherited together is greater than random (ie HLA allele and a gene for a specific disease inherited together)
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Term
Major Histocompatibility Complex
(MHC)
HLA Associations/Linkage disequalibrium
Examples 1
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Definition
Non-immune:
Narcolepsy DQB1*0602,DAQ10102
Hemachromatosis HLA-A*03
Infectious disease pathogenesis
Malaria (incr severity) HLA-B*53
HIV/AIDS (better prognosis) HLA B*51
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Term
Major Histocompatibility Complex
(MHC)
HLA Associations/Linkage disequalibrium
Examples 2
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Definition
Drug Hypersensitivity
TEN/SulfaHLA*A29, B812, DR7
Abacavir hypersensitivity HLA*B5701
Autoimmune Disease
Ankyl spondyl, Reactive Arthrit, Reiter's HLA B*27 RR100
Type I DM (HLA DR3, DR4, DQB1*0302 ) RR 5-25
Pemphigus Vulgaris DR4 (Ashkenazi Jews) RR 14
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Term
HLA Associations by Class |
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Definition
A3 - primary hemachromatosis
B8 - Graves' disease, celiac sprue
B27 - ankylosing spondylitis, inflammatory bowel, reiter, psoriatic arthritis
DR2: Goodpastures, allergy, MS, narcolepsy, SLE
DR3: celiac sprue, DM I, SLE, Sjögren's
DR4 - DM type 1, RA, pemphigus vulgaris, lyme disease
DR5 - Pernicious anemia, Hashimoto's thyroiditis
a few mnemonics. (Note from SVB-found these...not mine)
Shaq's (#34) ass so fat he looks like he should have diabetes (DR3/4). His weight is hard on his knees too, so arthritis (4)
DR2 is MS (two words), Goodpasture's (two organs), SLE (Duran duran, two words, sang hungry like the wolf), and hay fever (about which I don't give two sh!ts)
B8: you ate some wheat, now the situation is grave
DR7: is steroid sensitive nephrotic syndrome...steroids work you lucky duck (7)
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