Characterization of Cytolytic Effector Cells in Peripheral Blood of Healthy Individuals and Cancer Patients

Abstract

Abstract Peripheral blood lymphocytes from patients with transitional cell carcinoma of the urinary bladder, from control tumor patients, and from healthy individuals were fractionated on columns retaining 1) cells with Fc-receptors for IgG, as defined by rosette formation with IgG-coated erythrocytes, 2) cells with surface-bound immunoglobulin, or 3) cells with both types of surface markers. The spontaneous cytotoxicity of these lymphocytes against allogeneic or autochthonous tumor cells of bladder carcinoma or unrelated origin was studied in a 51Cr-release assay. The cytotoxicity to allogeneic target cells of lymphocyte fractions depleted of B cells (SIg+ cells) was only slightly reduced, unchanged, or, occasionally, augmented when compared to that of unfractionated lymphocytes. Fractions containing the majority of the B cells present initially but depleted of most of the Fc-receptor-bearing lymphocytes (EA+ cells) displayed a strongly reduced cytotoxicity against the same tumor cells. These effector cell fractions were also depleted of a majority of the complement receptor-bearing lymphocytes (EAC+ cells) and of a minor but significant fraction of T cells (E+ cells) and of a minor but significant fraction of T cells (E+ cells). Removal of both SIg+- and Fc-receptor-bearing cells gave the same results. Thus, in most instances, the spontaneous cytotoxicity against allogeneic tumor cells of fractionated lymphocytes was similar to their K cell activity against chicken erythrocytes (Ec) in the presence of rabbit anti-Ec antibodies (preceding paper). In conjunction with other data on the immunoglobulin dependence of this spontaneous cytotoxicity these results suggest that a significant fraction of this reactivity, displayed by both tumor patients' and normal individuals' lymphocytes, may be antibody dependent. The antibodies may either be carried over cytophilically during lymphocyte isolation or may be formed and released by some antibody-producing cells during the in vitro incubation. In two cases, in which bladder cancer patients' lymphocytes were tested with both autochthonous and allogeneic target cells, the effector cells killing the autochthonous target cells were neither B cells nor Fc-receptor-bearing cells. These results suggest that different effector mechanisms were involved in these cases.