Immunization by gamma‐IFN‐treated B16‐F10.9 melanoma cells protects against metastatic spread of the parental tumor

B16‐F10.9 is a highly metastatic clone of the B16‐F10 melanoma line, that expresses low levels of MHC class‐l antigens. F10.9 cells transfected with H‐2K^b are highly immunogenic and consequently exhibit a low metastatic phenotype. Treatment with γ‐IFN elevated H‐2K^b and H‐2D^b cell surface expression of F10.9 cells to levels much higher than did transfection of these genes. Yet, following intravenous injection, the γ‐IFN treated cells generated high loads of lung metastases. However, when tested for their immunogenic effect, they elicited CTL and were sensitive to CTL. Immunization with both the positive transfectant KI and the γ‐IFN‐treated F10.9 cells protected in vivo against metastatic spread of a subsequent transplant of parental F10.9 cells. The protection elicited by KI trans‐feet ants was more effective than the protection by γ‐IFN‐treated cells.