Presence of a specific immune complex in the cell-free ascites of a spontaneously metastasizing rat mammary adenocarcinoma, TMT-081.

We have previously reported that a mammary tissue-specific antigen (MTA) occurs in the circulation of rats bearing the metastatic mammary tumor, TMT-081. In this communication we present immunochemical evidence that MTA also exists in the form of a soluble immune complex in the sera and ascites of TMT-081-bearing rats. This immune complex, however, has no effect on the growth of TMT-081 in rats. Neither the MTA nor the immune complex could be detected in the circulation of lactating rats or rats bearing the nonmetastatic mammary tumor, MT-100. Thus, it appears that the spontaneously metastasizing tumor, TMT-100, considered previously to be nonimmunogenic or weakly immunogenic by conventional tests, does in fact elicit an apparently ineffective humoral response as manifested by the formation of an immune complex containing MTA.