Analysis of circulating immune complexes from patients with ankylosing spondylitis by gel electrophoresis and immunoblotting using antiserum against a psoriasis associated retrovirus-like particle.

Circulating immune complexes (CIC) were isolated from patients with ankylosing spondylitis (AS) and healthy blood donors by isopycnic ultracentrifugation in sucrose gradients. The CIC were analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. The major components of the CIC were identified as albumin, immunoglobulins, and complement factors. A 70 kD component and several low molecular weight components (Mr 19 kD and 14 kD (doublet] were detectable only in CIC from patients with AS. An antiserum raised against the envelope glycoprotein, gp70, of a psoriasis associated retrovirus-like particle was applied to check for cross reacting activity. This antiserum reacted with both a 70 kD and a 40-45 kD component in CIC from three out of six patients but not with CIC from any of the blood donors.