Assessment of syngeneic cell-mediated immunity to mouse mammary tumors by three different assays

Summary The purpose of this study was to compare the MCT, CRT, and Winn assays for assessment of CMI to syngeneic tumors. Spontaneous and MMTV-induced mammary tumors in Balb/c and Balb/cfC₃H mice were used. LNC were obtained at various times relative to S.C. injection of sensitizing tumor cells and surgical removal of the outgrowth. In direct comparison to Winn assays, CRT often gave false negatives (i.e., LNC could inhibit tumor growth in the Winn assay without being cytolytic), but when LNC were cytolytic in the CRT, they inhibited in Winn assays. Thus, a positive CRT was associated with a positive Winn assay. In contrast, results from MCT tests were generally not associated with those obtained by CRT or Winn assays. This divergence in assays was independent of differences in status of the LNC donor. With all three assays, stimulation of tumor growth or increased survival was occasionally observed. For the CRT this was manifested in the release of smaller amounts of ⁵¹Cr in the presence of immune LNC than in the presence of normal LNC. For MCT and Winn assays it was seen in better tumor growth after treatment with LNC than after treatment with medium alone. Detection of this phenomenon was independent among the three assays.Data from the CRT and Winn assays were analyzed to see whether they correlated with in vivo behavior of the sensitizing tumors. Detection of CMI by these tests was associated with tumors growing out after relatively long latency periods, but was independent of tumor growth rate. This is in contrast to our previously reported analysis of MCT data, in which detection of CMI was associated with slower growth rate but was independent of the latency period (Hager et al., 1978).Abbreviations CMI cell-mediated immunity - CRT chromium-release test - MCT microcytotoxicity test - MMTV murine mammary tumor virus - LDA lymphocyte-dependent antibody - LNC lymph node cells - SBF serum-blocking factors - SC subcutaneous - TCM tissue culture medium