OPSONIC EFFECT OF THE ALTERNATIVE COMPLEMENT PATHWAY ON CHANNEL CATFISH PERIPHERAL-BLOOD PHAGOCYTES

This study determined the effect of the alternative complement pathway (ACP) on neutrophil and monocyte phagocytes from peripheral blood of channel catfish, Ictalurus punctatus. Fluorescent-labeled latex micros pheres, Edwardsiella ictaluri and Escherichia coli were used to quanti fy phagocytic attachment and ingestion. Activation of the ACP enhanced the attachment of bacteria and microspheres to neutrophils and monocy tes. Activation of the ACP by serum opsonization of Esherichia coil in creased its ingestion by neutrophils in comparison with Edwaidsiella i ctaluri and microspheres. Inactivation of the ACP and C3b diminished a ttachment by neutrophils and monocytes, and ingestion by neutrophils o f microspheres and bacteria. Ingestion by monocytes was not affected b y activation of the ACP. In the present study, we found that the ACP f unctions in opsonophagocytosis in catfish and that ingestion by neutro phils was especially enhanced.