IMMUNE-COMPLEX DETECTION AND COMPLEMENT ACTIVITY IN RHEUMATOID-ARTHRITIS - COMPARATIVE-STUDY OF A RADIOIMMUNOASSAY USING MONOCLONAL RHEUMATOID-FACTOR, GEL-DIFFUSION TECHNIQUES AND C4 ACTIVITY

Abstract

Paired sera and synovial fluids from 49 patients with rheumatoid arthritis [RA] and 25 with other forms of arthritis were tested for immune complexes by a radioimmunoassay using monoclonal rheumatoid factor and gel diffusion procedures with monoclonal rheumatoid factor and C1q [fragment of complement component 1]. Synovial fluid hemolytic C4 and C4 adjusted for Ig[immunoglobulin]G concentration were determined in both groups of patients. Immune complexes were detected at similar high frequencies in the rheumatoid synovial fluids by precipitin formation with monoclonal rheumatoid factor (68%) and C1q (71%). Immune complexes in rheumatoid sera were detected in low frequency by precipitin reactions with monoclonal rheumatoid factor (10%) and C1q (0%). Using the monoclonal rheumatoid factor radioimmunoassay, 31 (63%) synovial fluids exceeded the mean non-RA binding activity by 1 SD. Similarly, 24 (49%) rheumatoid sera exceeded the mean non-RA binding activity by 1 SD. Synovial fluid C4 adjusted for IgG and IgG alone distinguished between the 2 groups of patients whereas the C4 values did not. The C4/IgG value showed a strong negative correlation with the monoclonal rheumatoid factor radioimmunoassay and C1q precipitin formation.