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

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Abstract
To characterize the effector cells involved in ADCC in a model system (lysis of 51Cr-labeled chicken erythrocytes induced by rabbit IgG antibodies), in “spontaneous”, and in tumor-associated cytotoxicity, we prepared subpopulations of peripheral blood lymphocytes from healthy individuals and from cancer patients by fractionation on columns according to three different principles. Columns with anti-immunoglobulin activity but lacking Fc-structures (F(ab′)2/anti-F(ab′)2 columns) removed ∼99% of the SIg+ cells (B cells), but only ∼20% of the Fc-receptor-bearing cells, as characterized by rosette formation with IgG-coated bovine erythrocytes (EA+ cells), and ∼25% of the complement receptor-bearing cells (EAC+ cells). Cells with receptor for sheep erythrocytes (E+ cells) were enriched. The K cell activity of this fraction was unchanged. Columns charged with immune complexes (OA/anti-OA columns) which display no anti-immunoglobulin activity retained ∼70% of the EA+ cells but only ∼20% of the SIg+ cells. About 50% of the EAC+ cells and ∼10% of the E+ cells were also removed. The K cell activity of this fraction was strongly reduced. IgG/anti-IgG columns very efficiently remove SIg+ cells, EA+ cells, and EAC+ cells whereas E+ cells are enriched. Again K cell activity is strongly reduced. The results indicate that B cells with high density SIg are inactive in the K cell assay and that the majority of mature B cells either have Fc-receptors of low avidity or have receptors for immunoglobulin which are qualitatively different from the Fc-receptors of SIg- cells. Furthermore, a significant fraction of the lymphocytes with complement receptors is different from these B cells. It can also be inferred that a significant subpopulation of the cells with receptors for sheep erythrocytes also have Fc-receptors for IgG. The cytotoxicity of these different lymphocyte fractions against a variety of human tumor cells will be reported in the following paper.

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