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J. Biochem, 1988, Vol. 104, No. 3 383-387
© 1988 Japanese Biochemical Society

research-article

The Different Roles of Two Distinct Fc{gamma} Receptors on Guinea Pig Macrophages in the Phagocytosis of Sensitized Sheep Erythrocytes1

Tohoru Nakamura, Hideki Sato, Toshiro Shimamura and Jiro Koyama2

Department of Hygienic Chemistry, Faculty of Pharmaceutical Sciences, Hokkaido University Kita-ku, Sapporo, Hokkaido 060

2To whom correspondence should be addressed

The functional roles of two distinct types of Fc{gamma} receptors (Fc{gamma}1/{gamma}2R specific for both IgG1 and IgG2, and Fc{gamma}2R specific for IgG2 alone) on the surface of guinea pig macrophages in the phagocytosis of sensitized sheep erythrocytes (EA) were investigated by the use of two Fab's of monoclonal anti-Fc{gamma}1/{gamma}2R and anti-Fc{gamma}2 R antibodies. The binding and subsequent ingestion of IgG1 antibody-sensitized erythrocytes (EA{gamma}1) by macrophages were completely inhibited by anti-Fc{gamma}1/{gamma}2R Fab', indicating that the reactions are mediated only by Fc{gamma}1/{gamma}2R. On the other hand, the binding and subsequent ingestion of IgG2 antibody-sensitized erythrocytes (EA{gamma}2) were substantially inhibited by anti-Fc{gamma}2R Fab', but not by anti-Fc{gamma}1/{gamma}2R Fab'. The inhibitory activities of anti-Fc{gamma}2R Fab' were dependent upon the amount of IgG2 antibody bound on erythrocytes; increasing the amount of bound IgG2 antibody from 0.15 to 0.91 µg/2×108 erythroeytes resulted in a decrease in the inhibition of binding of EA{gamma}2 by anti-Fc{gamma}2R Fab' from 50 to 0%, and also a decrease in the inhibition of ingestion of EA{gamma}2 from 100 to 50%. Since the binding and the ingestion of EA{gamma}2 by macrophages were completely inhibited in the presence of both anti-Fc{gamma}2R and anti-Fc{gamma}1/{gamma}2R Fab', Fc{gamma}2 seems to preferentially operate in these reactions, and Fc{gamma}1/{gamma}2R does not seem to operate unless the Fc{gamma}2R on the same macrophage is blocked by anti-Fc{gamma}2R Fab'. The finding that the avidity and ingestive activity of macrophages for EA{gamma}2 are higher than those for EA{gamma}1 also indicates that Fc{gamma}2R functions more effectively in the binding and ingestion of EA than Fc{gamma}1/{gamma}2R. These different abilities of Fc{gamma}2R and Fc{gamma}1/{gamma}2R do not seem to be caused by any difference in their affinities for EA, since ovalbumin-complexed IgG2 antibody was found to bind to Fc{gamma}2R with an association constant essentially equal to that to Fc{gamma}1/{gamma}2R.

1This work was supported in part by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture of Japan.


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