Guinea pig peritoneal macrophages. Differential effects of lectins on interaction with IgG immunoglobulins.

Guinea pig peritoneal macrophages have on their surface two receptors, one (Fc gamma 1/gamma 2 R) binding both guinea pig IgG1 and IgG2 and the second (Fc gamma 2R) binding only IgG2 immunoglobulins. We have previously shown that treatment of macrophages with neuraminidase or glycosylation inhibitors affects, in a different way, the binding of guinea pig IgG1, IgG2, and rabbit IgG. In the present study we have shown that pretreatment of guinea pig macrophages with lectins (Con A, WGA, and PNA) also has a different effect on the interaction of the cells with IgG. The lectins increased the binding of guinea pig IgG1, whereas rabbit IgG and guinea pig IgG2 were bound with a lower efficiency than in the case of control cells. Since sialic acid residues seem to modulate the activity of receptors and WGA interacts with sialylated oligosaccharides, we determined the IgG-binding characteristics for WGA-pretreated macrophages. We found that the increase in IgG1-binding ability was caused by an increase in the value of Kapp, but the number of IgG-binding sites was lower than in the control cells. In the case of rabbit IgG and guinea pig IgG2 we observed a decrease of both the value of Kapp and the number of IgG-binding sites. WGA did not interact directly with the Fc gamma receptor. The results of our former papers and the different effects of lectins of various specificities described in this paper suggest different positions of Fc gamma 1/gamma 2 and Fc gamma 2R in the plane of the macrophage membrane in respect to various membrane glycoconjugates.(ABSTRACT TRUNCATED AT 250 WORDS)