The activity of regional nodes in the evolution of immune responses to allogeneic and isogeneic tumors.

The evolution of immune responses of C57BL/6 mice to allogeneic tumor Sarcoma 180 and of A/J mice to isogeneic tumor Sarcoma 1 was investigated by colony and cell inhibition (CI) assays. The immune response of lymphocytes from regional popliteal nodes, distant nodes, and spleens was examined at varying times after s.c. implantation of known numbers of in vitro-grown tumor cells in the hind feet. In the allogeneic system, only regional node lymphocytes produced CI activity, amximum response appearing at Day 14 and gradually diminishing therafter with tumor regression. Serum-blocking activity was not observed until Day 21 and increased to significant levels by Day 39 when no lymphocyte CI activity was detectable. In the isogeneic system, CI activity was tumor-dose dependent. Responses to low-dose inocula were confined to regional nodes, whereas with high-dose inocula, initial responses were provided by regional nodes, but by Day 21 the spleen had become the primary source of CI activity. Examination of blocking activity in this system was not possible due to nonspecific serum cytotoxicity. Lymph nodes other than regional showed no CI response at any time in either tumor system. These studies demonstrate the importance of regional nodes in the development of immune responses to both allogeneic and osogeneic tumors.