Distribution of MHC class II alleles in primary systemic vasculitis.

Previous studies have shown a number of different associations between major histocompatibility complex (MHC) alleles and primary systemic vasculitis. Disease heterogeneity and the lack of specificity of certain MHC typing techniques may have contributed to the lack of consistency in those studies. We therefore studied a relatively homogeneous group of 94 patients with Wegener's granulomatosis, microscopic polyangiitis, or renal-limited vasculitis using molecular techniques that allow more precise assignment of MHC genotype. DNA was prepared from peripheral blood and DRB1 genotype determined by Taq restriction fragment length polymorphism. DQB1 and DPB1 genotype were assigned by polymerase chain reaction amplification followed by probing with allele-specific oligonucleotides. Specificity of associated anti-neutrophil cytoplasm antibodies (ANCA) was determined where possible by solid phase immunoassays using purified proteinase 3 (PR3) and myeloperoxidase (MPO). After correction for multiple comparisons there were no significant differences in the distribution of DRB1, DQB1 and DPB1 alleles between a local control group (N = 90 for DRB1, N = 50 for DQB1 and DPB1) and the patient group as a whole (N = 94) or two a priori defined subgroups (anti-PR3 positive, N = 35; anti-MPO positive, N = 22). We have therefore found no significant association between primary systemic vasculitis and any MHC class II allele. This, together with the fact that previous smaller studies have shown no consistent association, suggests that any such association is very weak, if it exists at all.