Fcγ-receptor-bearing, non-B lymphocytes in human peripheral blood: Cytophilic immunoglobulin binds almost exclusively to large granular lymphocytes

Abstract

Cytophilic IgG (CYT-Ig) has previously been reported to bind to both the “T G” (E +, FcγR +) and “L” (E −, FcγR +) subsets of non-B lymphocytes in human peripheral blood. Present investigations show that IgG-binding cells, as detected by a sensitive antiglobulin resetting reaction, are contained almost entirely within the large granular lymphocyte (LGL) subpopulation, and that fewer than 5% of other non-B lymhocytes acquire IgG from serum. Cell membrane-bound IgG sterically blocks the reaction of LGL with sheep red blood cells and therefore influences the proportions of these cells characterized as T G (E +) or L (E −) lymphocytes. Although the majority of T G lymphocytes are LGL, a further subpopulation of E +, FcγR + cells are detectable under particular test conditions. Unlike LGL, these lymphocytes do not react with rabbit IgG-coated ox RBC (EA G) in saline, but will form EA G rosettes when the reaction is enhanced in the presence of Ficoll. These FcγR + cells are mostly of typical small-lymphocyte morphology and do not bind detectable amounts of CYT-Ig, nor do they express the monoclonal antibody-defined VEP 13 determinant associated with FcγR on LGL.