In situ Fc receptor-bearing cells in two murine tumors. I. Isolation and identification.

The in situ inflammatory response was studied in 2 different tumors, the T1699 mammary adenocarcinoma in inbred DBA/2 mice and a sarcoma induced in inbred C57BL/6 mice by murine sarcoma virus. The presence of Fc receptors (FcR's) on infiltrating host cells was determined by rosette formation with antibody-coated sheep red blood cells (EA). Differences in FcR-binding activity among various cells were detected with the use of EA prepared with a range of antibody concentrations. Cells bearing FcR represented one-third or more of the inflammatory cell population in both tumors. The FcR-positive cells were heterogeneous in regard to both cell type and FcR activity. Monocytes and macrophages had greater FcR activity than did lymphocytes. Different populations of FcR-positive cells could be isolated by their EA-binding characteristics.