Immune-complex-induced transglutaminase activation: its role in the Fc-receptor-mediated transmembrane effect on peritoneal macrophages

The binding of soluble immune complexes (IC) or haemolysin-sensitized erythocytes (EA) to the Fc receptor of rat peritoneal macrophages was followed by a rapid increase of macrophage transglutaminase activity measured in cell homogenates and a time-dependent incorporation of ¹⁴C-methylamine into proteins of the intact cells. Methylamine, a competitive substrate inhibitor of transglutaminase could inhibit EA rosette formation as well as the soluble IC- or EA-induced lipid reordering of the plasma membrane of macrophages. Cytochalasin B (CB) which prevents EA rosette formation as well as IC-induced lipid reordering did not affect the stimulation of transglutaminase activity by IC. The possible relation of transglutaminase activation, lipid reordering and the contractile system to each other in the IC (multivalent ligand)-induced Fc receptor redistribution is discussed.