Variants deficient in phagocytosis of latex beads isolated from the murine macrophagelike cell line J774.

Abstract

Variants that lack the ability to ingest latex beads were isolated from the mouse macrophagelike cell line )774. Carboxylated latex beads were derivatized with polylysine and then daunomycin by a carbodiimide method . Cells that ingested such beads were killed ; variants that survived were isolated . Variants were detected at very low frequency and only after nitrosoguanidine mutagenesis . Of 11 independent isolates, 10 showed a lowered rate of uptake of polystyrene beads (without daunomycin) . All of these proved normal in rate and extent of Fc-mediated phagocytosis. There was essentially no change in sensitivity to free daunomycin in the variants compared to the parent . These results support the previous hypothesis that there are differences in the metabolic routes of receptor-mediated and nonspecific phagocytosis.Phagocytosis, one ofthe important differentiated functions in macrophages, has been grouped into receptor-mediated and receptor-independent or general phagocytosis (1) . Among the receptors that mediate the former process are the Fc receptors which recognize the Fc portion of antibody (2, 3), the C3b receptor that recognizes the C3b fragment of the complement protein C3 (4, 5), and a receptor for fibronectin (6) ; some evidence suggests that the receptor for pinocytosis of mannose, fucose, and N-acetyl-glucosamine-terminated glycoconjugates (7, 8) can also function in phagocytosis (9) . Several previous studies suggest that there are some different essential metabolic steps for receptor-mediated and general phagocytosis, in addition to the obvious lack of receptors for the latter. Thus, Michl et al . (10) showed that under certain conditions 2-deoxyglucose inhibited receptor-mediated phagocytosis, in a mannose-reversible process, but did not inhibit either receptor binding or general phagocytosis . In other experiments, Muschel et al . (11) isolated variants of a macrophagelike cell line that were defective in Fc-mediated phagocytosis although they possessed Fc receptors; such variants were able to phagocytose via general phagocytosis . These findings suggest that some of the processes subsequent to receptor recognition differ for each type of phagocytosis. To study this phenomenon it would be helpful to have variants that are the reverse of the ones found by Muschel et al . (11); in other words, ones that cannot phagocytose via generalized phagocytosis, but can do so via receptor-mediated phagocytosis. We herein report 2198 SEIICHI TAKASAKI, FRANZ EMLING, and LORETTA LEIVE