| Abstract: | Release of the lysosomal enzyme beta-glucuronidase from human neutrophils was induced by IgG or its Fc fragment, aggregated by immune precipitation or by coating on latex particles. Such release was inhibited when the cells were preincubated with free IgG or Fc fragments; F(ab')2 fragments were ineffective in both inducing and inhibiting beta-glucuronidase release. Neutrophils incubated with IgG or Fc fragments, when challenged with anti-IgG antibody, released lysosomal enzymes without the release of the cytoplasmic marker lactic dehydrogenase; These studies indicate that human neutrophils have surface receptors for the Fc portion of IgG. Neutrophils treated with IgG or its Fc fragment and subsequently with fluorescein- or ferritin-labeled anti-IgG showed binding of Fc or IgG to the cell membrane. Under suitable conditions, polar capping of labeled antibody was seen by fluorescence or electron microscopy. These studies suggest that the immunoglobulin receptors on neutrophils are redistributed when they are cross-linked with antibody. Fluidity of the membrane receptors appeared to be time and temperature dependent. Compounds such as 2-deoxyglucose, colchicine, and cyclic AMP, which inhibit the release of lysosomal enzymes, also inhibited the redistribution of the surface receptors. Cytochalasin B, an agent which increases the release, was found to increase the receptor redistribution; The relationship between the release of lysosomal enzymes and receptor mobility is discussed; |
