Circulating immune complexes in the seronegative spondyloarthropathies

Abstract

Circulating immune complexes (CIC) were determined in a large population of patients with seronegative spondyloarthropathies. In addition, we attempted to correlate the presence and levels of CIC with other parameters of disease activity in a serial fashion. CIC were measured using the Raji cell assay and the solid-phase Clq assay. A total of 92 patients were studied. These included 30 with ankylosing spondylitis (AS), 30 with psoriatic arthritis (PsA), 20 with Reiter's syndrome, and 12 patients with Crohn's arthritis (CA). Elevated levels of CIC were found in 73.3% (22 of 30) of AS patients, 60% (18 of 30) of PsA patients, 80% (16 of 20) of Reiter's patients, and 67% (8 of 12) of Crohn's patients studied. Both assays yielded concordant results. There was a significant correlation with disease activity, in particular arthritis, and the levels and incidence of CIC markedly declined in all groups when disease activity was under better control. Density gradient analysis of several sera revealed immune complex reactive material mainly in the 19 S region. This study suggests that CIC may play a role in the pathogenesis of some of the clinical manifestation of these conditions.