Increased immunogenicity of TA3-Ha cells treated with the antitumor antibiotic macromomycin (B).

Suspension cultures of TA3-Ha mouse mammary tumor cells were treated in vitro with a single dose of macromomycin(B) (MCR) at 1 mug/ml for 24 hours. This dose, which is cytostatic but not lethal, increased the immunogenicity of the cells. Adoptive transfer of spleen cells sensitized to MCR/TA3-Ha cells evoked an immune response against MCR-treated TA3-Ha cells but not against normal TA3-Ha cells. The therapeutic effect of MCR treatment (in this case) was, to a very small extent, due to the cytostatic action and more profoundly to the increased immunogenicity of the cells so treated.