HLA Class III Complement Genes and Susceptibility to Systemic Lupus Erythematosus (SLE)
Susceptibility to systemic lupus erythema (SLE) is partly governed by genetic factors. Among those implicated are genes within the HLA region. Originally, the strongest association between susceptibility to SLE and HLA gene products was with the class II HLA antigens, particularly DR3 and DR2 in Caucasoid populations. However, recent evidence indicates that the classical pathway complement genes located in the class III region (C2,C4A,C4B) are more closely associated. Among the polymorphic variants of these genes are so-called null or silent alleles, which result in non-expression of the relevant protein; some, but not all, null alleles are due to gene deletions. There is strong linkage disequilibrium between the class III alleles and those of HLA-B and DR. Therefore, an association between an HLA-B or DR antigen and SLE may well be secondary to one with a C4 or C2 polymorphism.
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