A role for scavenger receptors in phagocytosis of protein-coated particlesin rainbow trout head kidney macrophages

In macrophages of higher vertebrates, Fc receptors and receptors for comple ment and other serum factors, are generally known to enhance the phagocytic process, In lower vertebrates like salmonid fishes, none of these or other phagocytic receptors have been thoroughly characterized, The purpose of th is study was to elucidate to what extent these and other receptors are invo lved in the process of phagocytosis in rainbow trout (Oncorhynchus mykiss) head kidney macrophages. We used tosyl activated, paramagnetic dynabeads (2 .8 mu m in diameter), specifically coated with I-125 labeled Atlantic salmo n (Salmo salar) IgM or bovine serum albumin (BSA) as phagocytic probes, The effect of complement opsonization was also investigated by incubating the beads in serum. Our results indicate that neither the Fc- nor the complemen t-receptor(s) were important for phagocytosis of these beads, Our data supp ort the idea that scavenger receptors are involved in phagocytosis in rainb ow trout head kidney macrophages, as the use of a competitive scavenger rec eptor ligand extensively decreased degradation of the labeled protein coat on the beads, (C) 1998 Elsevier Science Ltd. All rights reserved.