Triggering effects of opsonized-IgG antibody on the superoxide release in the phagosome and phagosome-lysosome fusion by pulmonary alveolar macrophages in rabbits.

We studied the triggering effects of opsonized-IgG antibody on the superoxide (O2-) release and phagosome-lysosome fusion in the phagosome of pulmonary alveolar macrophages (PAM). Both were histochemically assayed in the same cell to enable simultaneous observation, using the qualitative superoxide dismutase (SOD)-inhibitable nitroblue tetrazolium (NBT) reduction test and the acridine orange (AO) method. When PAM from normal rabbit lungs were made to phagocytize the IgG-treated yeasts, the cells showed the enhanced release of O2- which acted directly on the antibody-coated yeasts as an oxidant, and the enhanced phagosome-lysosome fusion that was inhibited by SOD and was closely related to the enhanced release of O2- in the phagosomes. In contrast, neither enhanced O2- release nor phagosome-lysosome fusion was observed in the PAM which phagocytized saline-treated yeasts. These results may suggest that the opsonized-IgG antibody enhances the O2- release in the phagosome, resulting in the enhanced phagosome-lysosome fusion.