[Comparative studies of Fc receptors for IgG on resting and activated mouse T lymphocytes using different methods]

Fc-receptors for IgG (Fc gamma R) on resting (i.e. freshly prepared) and mitogen (Con A) or alloantigen-activated mouse spleen T cells were compared using binding of different markers such as 125J-labelled immune complexes, 125J-labelled anti Fc gamma R monoclonal antibody, FITC-labelled aggr. IgG and sheep erythrocytes covered with specific antibody (EA rosetting). C3b receptors were detected by rosetting with sheep erythrocytes covered with antibody and complement (EAC rosetting). The electrophoretic mobility of the cells without or after binding of aggr. IgG was also tested. A number of differences between resting and activated T cells were found: After activation of T cells by mitogen or alloantigen, a proportion of Fc gamma R-positive cells increased two to four times. Fc gamma R number per Fc gamma R-positive cell seemed to be higher on activated then on resting cells. Fc gamma R-positive resting cells did not shed their Fc gamma R upon incubation at 4 degrees C followed by incubation at 37 degrees C, but Fc gamma R-positive activated cells shed a remarkable proportion of their Fc gamma R on the same conditions. Binding of aggr. IgG caused a decrease of electrophoretic mobility of activated but not resting cells. Fc gamma R-positive resting cells were also C3b receptor-positive, whereas Fc gamma R-positive activated cells had no detectable C3b receptors.