Immune reactivity to native type II collagen in rheumatoid arthritis assessed by the leukocyte adherence inhibition assay and radioimmunoassay.

Cellular immunity to native type II collagen as well as to rheumatoid and osteoarthritic synovial membrane homogenates was assessed in a leukocyte adherence assay (LAI) in patients with rheumatoid arthritis (RA). Eleven out of 14 RA patients (79%) were positive in the LAI assay, demonstrating increased reactivity to rheumatoid over osteoarthritic synovial extracts. Increased reactivity to native type II collagen was not noted in the LAI assay. Radioimmunoassay studies demonstrated that 3 out of 14 RA patients (22%) had circulating IgG rheumatoid factor. None of the 11 patients with osteoarthritic or seronegative arthritis had antibodies to native type II collagen or circulating IgG rheumatoid factor, although 2 subjects with ankylosing spondylitis yielded positive LAI results. Our results suggest that type II collagen is not the important constituent in rheumatoid synovial membrane extract responsible for the positive LAI results observed in rheumatoid arthritis patients.