Binding of Fc fragments of IgG from human and seven animal species to Mycoplasma salivarium cells

Abstract

Mycoplasma salivarium cells were demonstrated to bind human IgG Fc fragments. The binding capacity was 78.8% enhanced by incubation of the cell suspension in PBS with 0.25% trypsin at 37 degrees C for 1 h, but tended to fall after incubation with higher concentrations of the enzyme, and was 95.5% lower after incubation of the suspension without trypsin. Fc fragments of IgG from rat, swine, sheep, rabbit, goat, cow and mouse also bound to the organism cells with increasing affinity in this order. The affinity of human IgG Fc fragments was almost comparable with those of sheep and rabbit. Antigen specific IgG from goat (specific for gamma-chain of human IgG, and mu-chain of human IgM) and rabbit (specific for whole molecules of goat IgG) bound to the cells. Binding of goat IgG Fc fragment was inhibited in the presence of antigen specific goat IgG (specific for gamma-chain of human IgG). These results suggest that M. salivarium cells bind IgG from a variety of animal species via the Fc fragment.