Association of C1q- and conglutinin-binding immune complexes with high consumption of alpha-2-macroglobulin in synovial fluids of patients with rheumatoid arthritis.

The consumption of alpha-2-macroglobulin (a2M) by proteinases in synovial fluids (SF) was indirectly measured by determining trypsin binding to solid-phase immunoadsorbed SF-a2M. In addition immune complexes (IC) were assessed by the solid-phase C1q-binding assay as well as the solid-phase conglutinin binding assay in rheumatoid (RA; n = 25) and osteoarthritic (OA; n = 9) SF. Elevated levels were found as follows: a2M X proteinase complexes (a2M X P) in 73.5% (RA, n = 20; OA, n = 5), solid-phase C1q-binding IC (C1q-IC) in 52% (13 out of 25 RA-SF) and bovine conglutinin binding IC (KgB-IC) in 54% (13 out of 24 RA-SF). All OA-SF were in either IC assay negative. Consumption of a2M in OA-SF and seronegative RA-SF was not more than 15% of total SF-a2M, showing a mean value of 19.5 and 13.5 micrograms a2M X P/ml SF. Seropositive RA-SF had an a2M X P mean value of 96.4 micrograms/ml SF, which differed significantly (p less than or equal to 0.05) from the former two groups. Similarly, RA-SF which were negative in either IC assay had a low a2M X P mean value (20.0 micrograms/ml SF). This contrasted sharply with the a2M X P means obtained in IC-positive RA-SF, which amounted to 131.5 micrograms a2M X P/ml SF in C1q-IC positive RA-SF and to 110.4 micrograms a2M X P/ml SF in KgB-IC positive RA-SF, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)