Effect of pregnancy on immune complexes and rheumatoid factors in patients with rheumatoid arthritis.

Rheumatoid arthritis is associated with circulating and intra-articular immune complexes and rheumatoid factors. The clinical activity of rheumatoid arthritis improves during pregnancy in the majority of women, with exacerbation following delivery. Concentrations of immune complexes, as detected by the Clq-binding assay, the Clq-solid phase assay, and the monoclonal rheumatoid factor-solid phase assay, decreased during gestation, with elevations following delivery. Concentrations of IgM-rheumatoid factor and IgG-rheumatoid factor, analyzed by radioimmunoassay, changed variably during pregnancy, increasing in some patients and decreasing in others. When examined serially before, during, and following pregnancy, changes in the concentration of circulating immune complexes and/or rheumatoid factors corresponded with the clinical changes in three patients. These observations document the significant effect of gestation on the concentration of circulating immune complexes in patients with rheumatoid arthritis. They also support the role of these laboratory tests in monitoring the clinical course of rheumatoid arthritis.