Detection of cytotoxic lymphoid spleen cells from STU-mice with Moloney sarcoma by a 3H-proline microcytotoxicity assay.

A microcytoxicity assay with 3H-proline prelabeled target cells was used for the detection of sensitized lymphoid spleen cells from STU inbred mice inoculated with Moloney sarcoma virus (MSV-M) or ascitic MSV-M tumor cells. The target cell line was derived from ascitic MSV-M tumor cells. With regard to the specificity of the assay nonimmune slpeen cells displayed no or only a weak cytotoxicity against these cells, and this was also the case when 3H-proline-labeled secondary cultures of syngeneic mouse embryo cells were exposed to both sensitized and nonimmune spleen cells. The time-course pattern of the development of cytotoxic lymphoid spleen cells in STU mice inoculated intramuscularly either with MSV-M or ascitic MSV-M tumor cells was studied. At the stages of tumor development, peak tumor size, and tumor regression the lymphoid spleen cell preparations were found to have relatively strong cytotoxic activity independent of whether the tumor was induced by MSV-M inoculation or tumor cell transplantation. However, in the latter case effector cells appeared earlier and were demonstrable for a longer period than in MSV-M-inoculated mice. Anti-theta serum treatment of lymphoid spleen cells taken at the stage of peak tumor size abrogated the cytotoxic activity or diminished it considerably indicating a T-lymphocyte response.