DIFFERENCES IN THE INGESTION MECHANISMS OF IGG AND C3B PARTICLES IN PHAGOCYTOSIS BY NEUTROPHILS

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  • 1 January 1982
    • journal article
    • research article
    • Vol. 45  (4) , 727-736
Abstract
A prominent feature of the surface interaction between the human phagocyte and particles coated with IgG and complement component C3b is its remarkably discriminatory character. IgG primarily promotes ingestion; C3b primarily promotes attachment. In several systems the C3b molecule causes membrane pertubation as efficiently as the IgG molecule. Yeast particles coated with specific IgG or C3b were used as prey in a newly developed phagocytic assay. The number of particles interacting with polymorphonuclear leukocytes (PMN) was correlated with effector responses monitored as percentage ingested particles, superoxide anion production and sensitivity of the ingestion process to cytochalasin B. During phagocytosis only 60% of PMN-associated yeast-C3b particles were ingested compared with 95% of yeast IgG. In cytochalasin B treated PMN, where ingestion was virtually abolished, attached yeast IgG induced superoxide anion production; the same number of attached yeast C3b did not. Attempts to induce superoxide anion production in the C3b system failed by increasing incubation time, number of added particles or by increasing the concentration of the opsonizing protein. A low concentration of cytochalasin B (1 .mu.g/ml) decreased the IgG-dependent ingestion to 65% without affecting the C3b-dependent ingestion. The existence of different ingestion processes in PMN, one more basal ingestion process represented by the C3b-promoted ingestion independent of membrane activation and another active ingestion process represented by the IgG-promoted ingestion dependent on membrane activation and an active response of the PMN is indicated.