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MHC and disease association. Autoimmune disease Viral disease Neurologic disorders Allergic reactions. MHC genes and Pathogen defence. Significant associations of HLA Alleles with increased risk for various diseases.
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MHC and disease association • Autoimmune disease • Viral disease • Neurologic disorders • Allergic reactions
Significant associations of HLA Alleles with increased risk for various diseases
Population studies show association of susceptibility to IDDM with HLA genotype Affected siblings share 2 HLA haplotypes much more frequently than expected Certain HLA genotype are frequently found in diabetic patients DR3/4 tight linkage to DQb,
Position of the DQb chain affects susceptibility to insulin-dependent diabetes mellitus AA 57 forms a salt bridge Across the peptide binding cleft of DQ Possible explanation: 1.) Allelic variants of MHC molecules differ in ability to present the autoantigenic peptides to autoreactive T cells 2.) Shaping of the T cell repertoire
Hereditary hemochromatosis • Defective regulation of iron absorption • Disease associated with mutation in the nonclassical MHC class I gene HLA-H • Onset with 40 or 50 years, nonspecific symptoms • Iron overload and accumulation eg in the liver, leads to severe illness and cancer • HLA-H carries mutation at position 283 (no association with b2-microglobulin possible)
Significant associations of HLA Alleles with increased risk for various diseases • Both inherited and environmental factors play a role in the induction of autoimmune disease • Inbred mice show uniform susceptibility to autoimmune disease • But also other independly segregating disease susceptibility loci have been defined • Also amount of self antigen transcribed in the thymus plays a role
In the fight against viruses and tumors: high MHC I expression on target cells:good or bad ?? NK cell NK cell Lysis No lysis CD8 cell CD8 cell No Lysis Lysis Tumor cell: little MHC I Tumor cell: lots of MHC I