Demonstration of a specific receptor for human C5a anaphylatoxin on murine macrophages.

Open Access
Publisher Website
Google Scholar
Abstract
Human C5a [complement component 5 a] anaphylatoxin is a potent mediator of the acute inflammatory response. It triggers a wide variety of neutrophil responses after binding to a specific cellular receptor. This bioactive glycopolypeptide is also bound to a specific receptor found on murine resident peritoneal macrophages, thioglycollate-induced exudate macrophages and the murine [macrophage like tumor leukemia]cell line P388D1. The apparent Kd of the C5a receptor for each cell type is .apprx. 2 nM, but each cell expresses a differing number of C5a receptors. Resident macrophages appear to have an average of 2 .times. 105 binding sites/cell; thioglycollate-induced cells have only 4-5 .times. 104 binding sites. The continuous cell line P388D1 is intermediate between these 2 cell types, exhibiting 8-10 .times. 104 C5a receptors/cell. Neither murine lymphocytes nor the parent [mouse leukemia] cell line P388 displays a measurable number of C5a receptors. Macrophage receptor-C5a binding interactions are followed by cellular uptake and degradation of 125I-C5a, much as is observed with neutrophils. Binding of C5a to macrophages results in augmentation of the primary humoral immune response as well as enhancement of mixed lymphocyte reactions. C5a should not only be considered as an acute inflammatory mediator but as an immunopotentiating modulator as well, thus serving as a critical link between complement activation and subsequent immune response.