In Situ Fc Receptor-Bearing Cells in Two Murine Tumors. II. Role in Tumor Immunityo 2 o 3

Abstract

The functional role of cells bearing Fc receptors (FcR's) in 2 murine tumors was investigated. Host-derived inflammatory cells were isolated from sarcomas induced in inbred C57BL/6 mice by murine sarcoma virus (MuSV) and from T1699 mammary adenocarcinomas in inbred DBA/2 mice. FcR-positive and FcR-negative cell populations were isolated by rosette formation with antibody-sensitized sheep red blood cells (SRBC's) followed by velocity sedimentation separation. The use of various antibody concentrations for SRBC sensitization allowed separation of different mononuclear cell populatlons by their FcR-binding characteristics. Cytotoxic T-cells within the MuSV-induced sarcomas did not have detectable levels of FcR. Growth-inhibitory cells in the sarcoma were, in large part, FcR-positive macrophages. In the T1699 mammary adenocarcinoma, the specific growth-inhibitory effector cells found within the tumor had high FcR activity characteristic of the monocytic cell series. An additional cell population capable of mediating antibody-dependent cytotoxicity was also isolated; these cells were weakly positive for FcR. Two populations of cell types capable of passively transferring delayed hypersensitivity (OHS) were isolated from the tumor: 1) a minor population, FcR-positive but θ-antigen-negative and 2) a larger population, θ-antigen-positive but FcR-negative. The results indicate that FcR-positlve cells may have several different and important functions in tumors and that FcR-binding properties may be used to identify and isolate specific effector cell populations. With the use of antibody-coated SRBC rosette formation as the probe, most FcR-positive effector cells involved in antitumor immunity appeared to belong to the monocytic cell series. Thymus-derived cytotoxic or DHS effector cells appeared to have low or undetectable levels of FcR.