Abstract
The chronic production of IgM and IgG antiglobulins is a major feature of rheumatoid arthritis. This implies an abnormal interaction between rheumatoid leucocytes and IgG. A novel rosette assay employing rabbit Facb-coated calf red blood cells has been developed to study receptors for IgG on peripheral blood lymphocytes. Cells were obtained from groups of patients with rheumatoid arthritis (RA), osteoarthritis (OA), ankylosing spondylitis (AS), and healthy control subjects. Receptors for Facb were found on an increased proportion of lymphocytes from RA patients compared with the other groups tested. It has been shown that the Facb rosette assay detects a subpopulation of lymphocytes bearing receptors for the Fc region of IgG. This receptor is clearly capable of recognising and binding only the C gamma 2 domain within the Fc region. As such it shows different specificity from some other Fc receptors detected on mononuclear cells. The number of Facb rosette-forming lymphocytes in an individual sample correlated well with the number of cells bearing 'high avidity' Fc receptors. However, the incidence of these cells in RA patients could not be correlated with disease activity, disease duration, or levels of IgM and IgG rheumatoid factor. Thus increased Facb rosette cells may represent a fundamental imbalance of the immune response in patients with rheumatoid arthritis.