Receptors for the Chemoattractants C5a and IL-8 Are Clustered on the Surface of Human Neutrophils

Abstract

SUMMARYWe have used high-resolution field emission scanning electron microscopy with backscatter electron imaging to detect immunogold-labeled C5a and interleukin-8 (IL-8) receptors on human blood neutrophils. The receptors were labeled with receptor-specific antibodies in combination with secondary antibody conjugated to immunogold. When neutrophils were isolated in a "nonactivated" state, both of these receptor populations were expressed primarily in clusters on nonprojecting domains of the cell membrane. When these cells were double labeled for C5a and IL-8 receptors, intermixing of these receptor species in a common cluster was not found. When neutrophils were isolated in an "activated" state, by mixing the blood with N -formylmethionyl-leucyl-phenylalanine, the cells were seen to be elongated and ruffled at their anterior pole, but the C5a receptors did not disperse or redistribute on the surface of the peptide-activated cells. Analysis of the distribution of human C5a receptors expressed by transfected mouse L-cell fibroblasts showed the C5a receptors to be clustered, but expressed on nonprojecting and projecting domains of the cell surface. These observations provide new information on the topographical expression of leukocyte receptors involved in directing cell migration.

Staphylococcus aureusStaphopain A inhibits CXCR2-dependent neutrophil activation and chemotaxis

“…Staphopain A-treated neutrophils were stained with the three different antibodies and the membrane was stained using the lipophilic fluorescent carbocyanine membrane dye Did. In our buffer-treated controls, we observed that both CXCR2 and CXCR1 receptors are expressed in clusters on the neutrophil membrane, as described previously (Gray et al, 1997). In Staphopain A-treated cells, the N-terminus of CXCR2 was no longer detected, while the extracellular loop was intact ( Figure 5D).…”

Elastase Controls the Binding of the Vitamin D-Binding Protein (Gc-Globulin) to Neutrophils: A Potential Role in the Regulation of C5a Co-Chemotactic Activity

“…Indeed, it has been demonstrated recently that elastase localizes to the migrating front (pseudopod) of neutrophils responding to a gradient of platelet-activating factor (37). Chemoattractant receptors, including the C5a receptor, have been shown to cluster in the migrating front of leukocytes (61)(62)(63). However, we have never observed DBP-C5a receptor complexes by either co-immunoprecipitation or chemical cross-linking (R.R.K., unpublished observations), suggesting that the two proteins do not interact.…”

Defective Neutrophil Degranulation Induced by Interleukin-8 and Complement 5a and Down-Regulation of Associated Receptors in Children Vertically Infected with Human Immunodeficiency Virus Type 1

“…Other studies have demonstrated interactions between these receptors on PMNs. A study that used scanning electron microscopy to detect immunogold-labeled CD88 and IL-8 receptors showed that these receptor populations are expressed in clusters on nonprojecting domains on the PMN membrane (9). A unidirectional heterologous receptor desensitization between CD88 and the IL-8 receptors has been reported by Blackwood et al (3), in which prestimulation of PMNs with C5a resulted in a significant reduction in chemotaxis of these cells toward IL-8.…”