Immunological reactivity in ankylosing spondylitis. Circulating immunoblasts, autoantibodies, and immunoglobulins

Circulating immunoblasts were studied in 39 cases of ankylosing spondylitis. The results were compared with 20 normal subjects and a group of 39 patients with rheumatoid arthritis, Immunoblasts were found to be increased in 11 patients with ankylosing spondylitis and in 22 patients with rheumatoid arthritis in contrast to the controls who were found to have a normal lymphoid cell population in the peripheral blood. Fifteen patients showed raised levels of one or more class of immunoglobulin. Autoantibodies, including antinuclear factors, were negative in all cases. There was a correlation between raised immunoblasts and plasma viscosity but not with clinical assessment of activity. The increase of immunoblasts in the peripheral blood, together with the raised immunoglobulins supports the suggestion of an immunological basis for ankylosing spondylitis.