Receptors for the Third Complement Component on a Proportion of Large Granular Lymphocytes from Human Peripheral Blood

Abstract

Large granular lymphocytes (LGL) are nonadherent cells with cytoplasmic azurophilic granules, avid receptors for the Fc portion of IgG, and a paranuclear localization of alpha-naphthyl acid esterase or acid phosphatasc. LGL constitute the bulk of T_G cells (cells with receptors for sheep erythrocytes and for IgG molecules) and null cells (non-T, non-B cells). In the present study we demonstrate that 20–33% of the circulating human LGL express receptors for the third complement component (C3R). When T_G cell or null cell fractions from normal individuals or non-T cells from a patient with infantile agammaglobulinaemia (which contained almost exclusively LGL) were rosetted with erythro cytes coated with antibody and complement, a variable number of C3R-bearing cells were detected. Such cells were isolated and analysed further; the great majority of them displayed the cytochemical and ultrastructural features of LGL.