Comparison of immune complexes and complement components in arterial and venous blood of patients with rheumatoid arthritis.

Immune complexes (IC) are frequently found in the venous blood and synovial fluid of patients with rheumatoid arthritis (RA). Although IC are claimed to have a pathogenetic role in RA, there is generally poor correlation between different IC tests and between individual tests and clinical features. We have therefore sought differences in the levels of IC detected by the Clq binding assay (ClqBA) and the indirect polymorphonuclear phagocytosis test (IPPT) in the arterial and venous blood of 16 patients with RA and 6 disease control subjects to determine which IC are pathogenetically important. Complement components, IgA, IgG, and rheumatoid factor were also measured. Eight of 10 patients with clinically active RA had higher ClqBA results in arterial blood while IgA IC in the IPPT and most complement components were higher in venous blood. No such differences were seen in patients with inactive RA or controls. These results suggest that IC other than those containing IgA are not formed in limb tissues including the synovium and may explain the variable results previously seen in patients with RA.