Expression of HLA-B27 antigens on mononuclear leucocytes in ankylosing spondylitis.

Differences in expression of HLA-B27 antigens on immune competent cells might play a role in the susceptibility to environmental factors which may be responsible for the initiation of ankylosing spondylitis (AS). Using a quantitative complement-mediated lymphocytotoxity assay we determined the expression of HLA-B27 antigens on the membranes of mononuclear cells obtained from 20 patients with AS, four patients with other seronegative arthropathies and eight healthy controls. The variation in expression of B27 between individuals was quite extensive, but there was no significant difference in the mean titration curves obtained for each of the three groups. These findings suggest that the expression of HLA-B27 antigens on the membrane of mononuclear leucocytes does not play a role in the pathogenesis of AS.