Characterization by Monoclonal Antibodies of the Cytotoxic Effector Cells in Human Peripheral Blood Mononuclear Cells Reactive against Anchorage-Dependent Tumour Cell Lines

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Abstract
The effector cells for spontaneous cytotoxicity against anchorage-dependent human or mouse tumor cell lines in a 72 h iododeoxyuridine release assay by normal human peripheral blood cells (PBMNC) or monocyte-enriched fractions were analyzed with monoclonal antibodies. PBMNC or adherent or elutriated monocyte-enriched populations of PBMNC were depleted or monoclonal antibody-reactive cells by complement-dependent lysis or separated into monoclonal antibody-positive or -negative subsets by an indirect rosetting technique followed by Ficoll-Hypaque density gradient separation. In PBMNC and monocyte-enriched populations, an appreciable proportion of the effector cells with cytolytic activity against adherent human or mouse tumor target cells were positive with B73.1.1 (an antibody with a high degree of selectivity for natural killer (NK) cells), B43.4.1 (or OKM1) and with OKT11a (an antibody recognizing the receptors for sheep erythrocytes), and had the morphology of large granular cells, which have previously been shown to mediate NK activity. These effector cells were mostly negative for BRL.1, BRL.2, B52.1.1, B44.1.1, B13.4.1 and DR antigens, unlike classical monocytes. Some cells which are cytotoxic for the adherent mouse, SV-40-transformed kidney tumor line, TU-5, may bear B52.1.1 or other monocyte-like antigens. Thus, in monocyte-enriched populations, NK cells and monocytes have cytotoxic effector activity against various human and mouse adherent target cell lines.