CROSS-REACTIVE HLA-ANTIGENS IN B27-NEGATIVE REITERS SYNDROME AND SACROILIITIS

Abstract

Proposed mechanisms to explain the association of HLA-B27 with Reiter''s syndrome (RS) and ankylosing spondylitis (AS) include abnormal immune response genes linked to HLA or a direct role for HLA antigens in disease pathogenesis. These studies provide indirect evidence to support the latter hypothesis. Seventy-nine patients (44 with RS, 27 with AS and 8 with idiopathic sacroiliitis [SI]) were evaluated clinically and by HLA phenotyping. Of the 10 patients with RS who were B27-negative, 7 (70%) had another B locus antigen that was immunologically cross-reactive with B27 (B7-group antigen). These included B7 in 2, Bw22 in 4, and Bw42 in 1. Four of 8 patients with sacroiliitis alone had B27, but the remaining 4 all had B7. Two B27-negative AS patients had no B7-group antigens. Thus, 69% of B27-negative patients had cross-reactive HLA antigens.