Circulating Immune Complexes in Rats Bearing 6-Thioguanine-resistant Variants of the 13762 Mammary Adenocarcinoma1

The relationship between immune complex (1C)formation and tumor cell metastatic potential was investigated in rats inoculated in the footpad with parental 13762 mammary adenocarcinoma cells or 6-thioguanine-resistant (TGR) variant cells. These cell lines are either highly metastatic (13762), nonmetastatic (TGR), or occasionally metastatic (TGRrev, TGRrevM). The 13762 TGR rat tumor model thus provides the opportunity to examine host immune responses to tumor cells of different phenotypes, but derived from the same parent tumor line. 1C levels were low in 13762 tumor-bearing rats. In contrast, animals with TGR tumors had high levels of ICs in their sera, while animals bearing TGRrev and TGRrevM tumors had intermediate levels of ICs. In this rat tumor model system, 1C formation is inversely related to the metastatic potential of the tumor lines.