6533b820fe1ef96bd127a328

RESEARCH PRODUCT

The Receptor Functions of Endogenous C1q, a Subcomponent of the First Component of Complement, on Peritoneal Macrophages

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Abstract C1q, the Fc recognizing subcomponent of the first complement component was shown to be synthesized by peritoneal macrophages. Evidence is presented that C1q serves during the secretion phase as Fc binding protein on the membrane of these macrophages. A dose-dependent inhibition of Fc rosette formation occured when the macrophages were pretreated with anti-C1q -F(ab') 2 . The C3b rosette formation was not affected. In addition, preincubation of peritoneal macrophages with anti-C1q -F(ab') 2 abolished specifically the polyanion mediated stimulation to secrete dose and time dependently lysosomal enzymes. There was no polyanion-induced enzyme release after incubation of polyanions with highly purified C1q. These findings are compatible with the hypothesis that C1q produced by macrophages may serve in the macrophage membrane as an endogeneous receptor for Fc- and polyanionic molecules.