Regulation of macrophage migration by products of the complement system.

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Abstract
Agents that induce rapid macrophage spreading were examined for their ability to modify the migration of [mouse] macrophages in the capillary tube assay. Products of the activation of the contact phase of blood coagulation and the purified component Bb, the large cleavage fragment of factor B of the alternative complement pathway, produced a dose-dependent inhibition of migration. Inflammatory macrophages elicited with a lipopolysaccharide endotoxin or thioglycollate medium exhibited a rapid spreading and inhibited migration; resident cells did not. A close correlation existed between enhanced spreading and inhibited migration under in vitro induced and in vivo situations. Cleavage products of C5 [complement component 5] of the classical C pathway enhanced macrophage migration and did not alter spreading. In mixtures of C5 cleavage products and Bb, the predominant peptide determined the outcome of the reaction. Factor B, a normal secretory product of macrophages, may represent common substrate for several of the proteases that induce spreading, inhibit migration and lead to the generation of the enzymatically active fragment Bb.