Alteration of Fc-receptor phenotype and proliferative capacity of Fc-IgG-receptor positive lymphocytes through interaction with soluble immune complexes of patients with SLE or RA

Soluble circulating immune complexes (CIC) are a common finding in patients with systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) or other autoimmune diseases. The predominant immunoglobulin class of most CIC is IgG, which enables these CIC to bind to Fc-IgG-receptor expressing cells. In this study the interaction between soluble CIC from patients with SLE or RA and Fc-IgG-receptor positive lymphoid cells from healthy individuals was investigated. Similar to the effect observed with insoluble immune complexes, soluble CIC interact with Fc-IgG-receptor positive lymphoid cells and can induce a modulation of Fc-receptor expression. Fc-IgG-receptors are lost and Fc-IgM-receptors are expressed on the same cells after IC interaction and culturing the cells for 24 h. Simultaneously with this change of Fc-receptor phenotype the originally Fc-IgG-receptor positive cells demonstrate a decreased ability to proliferate upon mitogen stimulation. This change of phenotype and proliferative capacity correlates with the content of CIC in the sera of patients with SLE or RA.