Recovery of the in vivo cytotoxic T-cell response in cyclophosphamide-treated mice by injection of mixed-lymphocyte-culture supernatants.

Mice given injections of high antileukemic doses of cyclophosphamide lost the capacity to generate cytotoxic T-cells in vivo to allogeneic tumor cells. These low responses were not due to the elimination of cytotoxic T-lymphocyte precursors because normal cytotoxic responses were obtained in vivo after cyclophosphamide treatment by injection of helper factor derived from mixed-lymphocyte-culture supernatants.