I and i antigens of human peripheral blood lymphocytes cocap with receptors for concanavalin A

Abstract

Surface immunofluorescence experiments using a human anti-i and two anti-I antisera have been performed on human peripheral blood lymphocytes. These are known to contain cold-reactive monoclonal IgM antibodies against the carbohydratesequence: Galβ1→4G1cNAcβ1→3Galβ1domain (anti-I step) of another branched I-active structure, which is given in the text. A high proportion of B- and T-type lymphocytes express these I and i determinants. In the presence of anti-human immunoglobulin, the cold-reactive membrane-associated complexes of I-anti-I and i-anti-i become stabilized, and redistribution (with patching and capping) can be elicited at 37°C. Dual fluorescence experiments have shown striking concordant staining of I or i (fluorescein) caps and patches with concanavalin A (rhodamine) reactive sites on normal and leukemic cells, suggesting that a proportion of I and i active structures of lymphocyte membranes are structurally associated or physiologically coupled with glycoproteins carrying oligosaccharides with branched mannosyl cores.