Clinical correlates of circulating immune complexes in patients with recent yersiniosis.

Circulating immune complexes (CICs) and rheumatoid factor were studied in 31 patients with serologically confirmed yersiniosis (12 in a pilot series and 19 in a prospective series). Yersiniosis is an intestinal infection complicated occasionally by extraintestinal symptoms such as aseptic arthritis. Four tests representing three main principles (affinity of human platelets and of C1q for complexed IgG and of conglutinin for C3) were used for the detection of CICs, which were found in all patients. Fifty-five of 62 specimens of serum from the prospective series of 19 patients reacted positively in at least one test. The conglutinin-binding assay and the platelet-125I-labeled staphylococcal protein A test gave positive results most frequently (74% and 84% of the time). Mean levels of CICs were significantly higher in patients with prolonged gastroenteritis than in those with histocompatibility leukocyte antigen B27-positive arthritis. During follow-up, the mean level of CICs (as measured by the platelet-protein A test) decreased significantly in patients with arthritis, while CICs and rheumatoid factor persisted in patients with prolonged gastroenteritis.