Lymphocytes bearing Fc gamma receptors in rheumatoid arthritis. III. Immunoregulatory function associated with Facb rosette-forming cells.

Abstract

SUMMARY A subpopulation of mononuclear cells (PBMNC) that express Fc receptors with specificity for the Cy2 region of IgG may be detected by rosette formation with calf erythrocytes coated with the Facb fragmenit of rabbit IgG. These Facb-R' cells are found in increased numbers in the peripheral blood of patients with rheumatoid arthritis (RA). Studies have been carried out to identify the functional properties of these cells in healthy and rheumatoid subjects. Facb-R+ cells were shown to lack both natural killer and antibody-dependent cytotoxic activity. Depletion of Facb-R' cells from both healthy and rheumatoid PBMNC resulted in a marked suppression of pokeweed mitogen (PWM) stimulated IgG synthesis but had no effect on T cell proliferation induced by phytohaemagglutinin, concanavalin A, or PWM. The addition of Facb fragments to PBMNC cultures also caused inhibition of PWM-driven IgG production. In this assay rheumatoid PBMNC were significantly less sensitive to Facb-mediated suppression than healthy control cells. Our results suggest that Facb-R' cells are involved in the antibody-mediated feedback regulation of immunoglobulin synthesis aind that this mechanism is impaired in patients with RA.

Lymphocytes bearing Fc gamma receptors in rheumatoid arthritis. IV. Increased numbers and activation of Facb-R+ cells after immunisation of healthy individuals.

“…Previous data have suggested that the major function of Facb-R+ cells is as accessory cells in antibody production. 6 The increase noted in Facb-R' cell numbers after immunisation may therefore have functional significance. The effective induction of an immune response to specific antigen requires an adequate supply of accessory cells presenting antigens.…”

“…lymphocytes but that they express certain monocyte related markers and class II MHC antigens.5 Functionally, Facb-R+ cells are non-phagocytic4 and lack cytotoxic activity but act as regulatory cells in pokeweed mitogen driven IgG synthesis. 6 The factors which promote the increase in Facb-R+ cells in rheumatoid peripheral blood are unknown. Experiments in mice have shown that splenic Facb-R+ cells increase in number after secondary but not primary immunisation with a specific antigen, sheep erythrocytes.7 In view of this, numbers of circulating Facb-R+ cells have been monitored in healthy volunteers undergoing immunisation procedures and in cultures of PBMNC stimulated in vitro with specific antigen.…”