Immunodepression as a factor during 3‐methylcholanthrene carcinogenesis and subsequent tumour growth in mice

Abstract

CBA/H‐T6 mice received a dose of 3 or 6 mg 3‐methylcholanthrene on day 0 and their spleen cell IgM antibody response to sheep red blood cells was found to be significantly depressed 23 days thereafter. However, at this time, there was no reduction in the ability of spleen cells from these mice to induce a graft‐versus‐host reaction in (A × T6)F₁ hybrid animals. On day 68 after 3‐MC injection, six animals had developed tumours while six were still in the latent period. There was no difference in the capacity of spleen cells from these two groups of animals to induce a GvH reaction in F₁ hybrids. Three 3‐MC induced sarcomata were serially passaged in isogenic hosts. The growth rates of these tumours increased and the regional lymph nodes and spleens became progressively more hypoplastic in successive hosts. However, there was again no decline in immunocompetence of spleen cells as judged by the induction of a GvH reaction in F₁ hybrids. It is therefore suggested that the increase in tumour growth rate reflected a change in the tumour rather than increasing immunodepression of successive hosts.