Immunity as the predominant factor determining metastasis by murine lymphomas.

The metastatic behaviour of the L5178E (non-M) lymphoma and a highly metastatic subline L51787ES (M) were studied in syngeneic DBA2 mice. The non-M tumour rarely metastasizes in intact syngeneic mice, but produces extensive and rapidly lethal metastases when implanted into irradiated recipients. The metastatic behaviour of the M subline is unaffected by irradiation of the host. By conventional transplantation criteria, the non-M tumour is more immunogenic than the M subline. Both tumours, however, produce similar responses in a lymphnode weight-gain assay. Host-cell infiltration of the tumours growing s.c. is much greater in the non-M than the M, the infiltrating cells being Fc-receptor-positive and maturing into macrophages after 2 days in vitro. Although spontaneous in vitro motility of the M cells is much greater than that of the non-M, the metastatic behaviour of the tumours is clearly determined by host immunological responses.