Circulating immune complexes and immunoglobulin M-class rheumatoid factor in rats bearing mammary adenocarcinomas which vary in ability to metastasize.

In order to explore whether immune complex (IC) formation and immunoglobulin M-class rheumatoid factor (RF) synthesis are related to tumor progression, solid-phase enzyme immunoassays were used to test for ICs and RF in rats bearing three different syngeneic mammary adenocarcinomas. The mammary adenocarcinoma cell lines used produced either extensive metastasis (13762), metastasis in only a proportion of the animals given injections (R3230AC), or no metastasis (DMBA8). DMBA8 and 13762 tumor-bearing rats developed only low levels of circulating ICs. Of 18 animals bearing R3230AC tumors, four developed palpable lymph node metastasis (macrometastasis), while another five showed evidence of metastasis only upon histological examination (micrometastasis). R3230AC tumor-bearing animals which did not develop metastasis were found to have significantly higher IC levels than those rats with metastasis. Several sera from rats bearing R3230AC tumors were fractionated by molecular sieve chromatography. Most of the ICs in these sera were 7S to 19S in size. Significant RF synthesis occurred only in rats bearing R3230AC tumors and only during terminal tumor growth. These results show that IC formation and RF synthesis varies in animals bearing different mammary adenocarcinomas.