[Enhanced immunogenicity of xenogenized tumor cells in rats pretreated with cyclophosphamide (author's transl)]

Immunization with xenogenized tumor cells, tumor cells infected with murine leukemia viruses produced strong antitumor immunity. In this study, the immunogenicity of xenogenized tumor cells was compared in cyclophophamide-treated and nontreated rats. CY treatment 3 days before immunization with xenogenized tumor cells enhanced antitumor cell-mediated immunity and antibody responses. However, CY treatment after immunization had no effect. Transfer of thymus cells from normal rats before the tumor challenge abolished the CY-induced augmenting effect. From these results, it is suggested that the elimination of precursors of suppressor T-cells results in enhanced immunogenicity of xenogenized tumor cells.