Fc receptor-bearing cells as a reliable marker for quantitation of host lymphoreticular infiltration of progressively growing solid tumors.

Disaggregated cell suspensions made from transplanted solid tumors, either chemically-induced fibrosarcomas, or spontaneous mammary carcinomas, can contain very high numbers of Fc receptor-bearing cells which are of host origin. Because most types of lymphoreticular cells have Fc receptors, and because T cells--most of which are Fc receptor-negative--appear to infiltrate such tumors only to a very limited degree, the possibility that Fc receptor cells could serve as a reliable and simple marker for host lymphoreticular cell infiltration of solid tumors was tested. This was accomplished by comparing the ratios of Fc rosetting cells to serologically detectable host cells in H2d or H2k haplotype tumor cell suspensions grown in (H2d X H2k)f1 hybrid mice, where host cells could be distinguished from tumor cells by treatment with the appropriate anti-H2 serum. Ratios of 0.8 to 1.08 were obtained for four different tumors including the SaD/2 fibrosarcoma, a CBA spontaneous fibrosarcoma, and the T1699 and CaD/2 mammary carcinomas. Analysis of the results showed that enumeration of Fc rosettes was a reliable host cell maker for at least three of the four tumors tested. The mean non-malignant host cell content of the various tumors, as assessed by anti-H2 cytotoxicity tests, ranged from 23% to 41%.