Redistribution of mouse spleen cell Fc receptors following treatment with mouse or human aggregated immunoglobulin G

Mouse spleen cells treated with the Fc receptor ligands mouse IgG2b and human IgG, followed or not by a second antibody, exhibit different patterns of redistribution. In the work reported here we have examined the redistribution of Fc receptors (FcR) after binding of aggregated mouse IgG2b (Alg) or of Alg followed by anti-lg. We were particularly interested in learning whether binding of isologous Alg to FcR is followed by significant redistribution and shedding of Alg-FcR complexes. Mouse IgG2b alone will not induce capping even after 60 min at 37 degrees C. Human IgG induces some capping with minor shedding of complexes. Human IgG followed by anti-IgG readily induces capping by 15 min on 70% of the cells. This treatment also induces capping by 60 min at 20 degrees C on about 80% of the cells with a moderate degree of shedding of complexes. This is in agreement with the concept that the crosslinking required for FcR capping can be best induced with a second antibody. It is of interest, however, that heterologous IgG, unlike isologous, can induce a modest degree of capping and slight shedding even without the second antibody, suggesting that some crosslinking occurs with heterologous IgG.