[The significance of Fc-IgG and Fc-IgM receptors on human T-lymphocytes (author's transl)].

About 15-20% of human circulating T-cells express Fc-IgG receptors (TG cells), and about 70-80% have Fc-IgM receptors (TM cells). TM cell enriched fractions are functionally heterogenous cell populations. TM cells are able to mature into specific cytotoxic T-cells after mixed lymphocyte reaction; TM cell fractions also comprise the helper T-cells for pokeweed mitogen (PWM) induced B cell differentiation; and some TM cells can be induced to act suppressively on PWM induced B-cell differentiation and maturation. TG cells represent activated, relatively radiation resistant suppressor T-cells, and these cells are also active in natural cytotoxicity (NC), antibody dependent cellular cytotoxicity (ADCC) and mitogen induced cellular cytotoxicity (MICC). IgG-immune-complex interaction with the Fc-IgG receptor on TG cells modulates Fc-receptor expression as it leads to loss of Fc-IgG receptors and expression of Fc-IgM receptors on the original TG cells after culture. This modulation of surface markers is accompanied by functional changes since ADCC and suppressor cell activity is reduced following immunecomplex interaction. Fc-IgG and Fc-IgM receptor expression on human T cells seems therefore to characterize distinct functional stages of T cells. IgG immunecomplex interaction in vitro seems to be a potent tool to change the different functional stages.