Evidence to show MHC-linked factors other than HLA-B27 governing susceptibility to spondylo-arthropathies in Asian Indians.

The HLA antigen profile of 129 North Indian patients with ankylosing spondylitis, 66 patients with Reiter's syndrome and 57 patients with 'unclassifiable' arthritis was compared with 380 normal, healthy controls. Besides B27 which appeared with a significantly increased frequency in the three patient groups, other HLA antigens, viz. A2 and B35, showed deviated frequencies. The HLA supratype A2, B27 was found to be at an elevated frequency in patients with ankylosing spondylitis and unclassifiable arthritis whereas the B35, B27 combination showed a decreased frequency in our Reiter's syndrome sample. These data suggest that besides B27, other HLA-linked factors influence susceptibility to spondylitic disorders and might act as 'modifier' genes for the type and severity of spondylo-arthropathy in a B27-positive individual.