The adherence of leucocytes and platelets induced by fixed IgG antibody or complement.

Human, rabbit and guinea-pig neutrophils and rabbit and guinea-pig macrophages were shown to adhere to sheep erythrocytes sensitized with isologous IgG antibody (EAIgG). IgM antibody, however, was less active and use of rabbit IgM antibody to fix complement from different species allowed the examination of neutrophil, macrophage and platelet adherence to alexinated erythrocytes (EAIgMC′). Complement from twelve mammalian species induced the adherence of isologous neutrophils. On the other hand, platelets showed some variability. Ox, goat, sheep and pig platelets, like those from man and the baboon, did not adhere to EAIgMC′, although adherence of platelets from the rabbit, guinea-pig, rat, mouse, horse and cat was observed. C′3 was the complement component implicated in these reactions. Treatment of the leucocytes with trypsin prevented the adherence to EAIgMC′ but not to EAIgG. Chelation of free magnesium with EDTA inhibited the adherence of rabbit neutrophils, but not of human neutrophils, to EAIgMC′. EDTA had no effect on the adherence to EAIgG. Rabbit and guinea-pig neutrophils exhibited some species specificity towards the antibody and complement which would induce their adherence. This was not shown by human neutrophils or by rabbit and guinea-pig macrophages. The adherence of particles to phagocytes comprises the first stage of phagocytosis and the role of antibody and complement in this process is discussed.