Potentiation of hamster tumors by normal cells or charcoal.

Admixed spleen cells from normal animals or from animals given injections of Syrian hamster type C virus significantly potentiated the growth of the transplanted D9 lymphoma of random-bred hamsters. Potentiation was measured by an increase in incidence of tumors, a shortened latent period, and a decreased 50% tumor-producing dose of tumor cells. Intermediate doses of spleen cells (10 to 100 spleen cells per tumor cell) produced the greatest potentiation. Preincubation of admixed spleen and tumor cell suspensions in vitro was unnecessary. Immunization to isoantigens was not responsible for potentiation, since growth of a transplantable carcinoma of inbred hamsters was also facilitated by normal spleen cells. In addition, normal kidney or liver cells increased the incidence of tumors transplanted by a small number of tumor cells. Potentiation did not occur when spleen cells were injected at a site remote from the tumor cells. Since the potentiating cells might act eigher as a physical barrier to host response, or by blocking normal macrophage function, we injected charcoal with tumor cells. Simultaneous treatment with charcoal facilitated the growth of the lymphoma but not that of the carcinoma. Treatment with some doses of charcoal was also effective at distant sites. Although potentiation of tumor growth by cells or charcoal may operate through different mechanisms, these phenomena should be explored in regard to outgrowth of primary tumors, tumor immunity, or enhancement of tumor growth.