Assessment of host immune status during progressive growth and after excision of DNA virus (simian virus 40) tumors in hamsters: comparison of tumor-specific and tumor-unrelated parameters of immune responsiveness.

The kinetics of cell-mediated immunity to simian virus 40 (SV40) tumor-specific transplantation antigen (TSTA) were compared to the kinetics of tumor-unrelated parameters of immune responsiveness in the assessment of the immune statuses of inbred MHA/SsLAK hamsters during the course of progressive syngeneic SV40 tumor growth and after tumor excision. With the use of the tumor cell neutralization test in vivo and the macrophage migration inhibition assay in vitro, specific cellular immunity to SV40 TSTA was detected by 4 days after tumor cell inoculation, when the tumor was small. This tumor-specific immune response was no longer detected at 7 days after tumor cell inoculation, when the tumor had reached a mean diameter of 12.5 mm, but it returned by 14 days after surgical excision of the tumor. The patterns of host responsiveness to mitogens in spleen cells derived from tumor-bearing animals or from tumor-excised animals generally showed little or no correlation with the kinetics of tumor-specific cellular immunity. The kinetics of the humoral immune response to murine erythrocytes, as determined by hemagglutination assays, correlated much more closely with the kinetics of tumor-specific immunity than did the responses to mitogens. IgG antibody (T-dependent) responses were more affected by progressive tumor growth than were IgM antibody (T-independent) responses. The data suggest that results of tests with the use of tumor-unrelated parameters of immune responsiveness for the assessment of the immune status of cancer patients should be interpreted with caution.