Major histocompatibility complex, Class mutations

Asn25 of SEA) and amino acids 60-64 as essential for interactions with the murine V/3 chain. Mutations within the binding domains of SEA for major histocompatibility complex class II differentially affect interactions with the V/3 region of a T-cell receptor. " ... 

Leder L, Llera A, Lavoie PM, Lebedeva MI, Li H, Sekaly RP, Bohach GA, GahrPJ, Schlievert PM, Kaijalainen K, Mariuzza RA A mutational analysis of the binding of staphylococcal enterotoxins B and C3 to the T cell receptor beta chain and major histocompatibility complex class II. J Exp Med 1998 187 823-833. 

Finally, in this brief overview of lymphocyte defects, mention should be made of mutations affecting major histocompatibility-complex (MHC) Class II molecules. These mutations affect a multiprotein transcription factor complex that regulates the expression of MHC Class II molecules (121). Affected patients have undetectable levels of MHC Class II antigens HLA-DP, DQ, and DR on the surface of monocytes and B cells. Lack of these antigen-presenting molecules leads to impaired immune response. Affected individuals have moderate lymphopenia with a severely reduced number of CD4+ T cells and normal or increased numbers of CD8+ T cells. Since MHC molecules in the thymic epithelium play a key role in positive and negative selection of primitive T cells, selection of competent T cells is also affected in the absence of MHC Class II antigens. 

Not until 1996 did Feder and colleagues identify a novel major histocompatibility complex (MHC) class I-like gene in which homozygosity for specific mutations were found in 83% of patients with hemochromatosis. 

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