Analysis of immunosuppressor cells induced by immunization of solubilized tumor-associated antigens prepared from a rat fibrosarcoma.

Soluble tumor antigens were prepared from chemically-induced rat fibrosarcoma KMT-17 cells by sodium deoxycholate (DOC) extraction. Significant responses detected by the footpad assay and Winn assay were demonstrated in rats immunized with DOC extract. However, rats previously immunized with DOC extract showed a significant enhancement of tumor growth when challenged with KMT-17 cells. This enhancement was specific for the tumor line used. The tumor-neutralizing ability of KMT-17 immune spleen cells was abrogated when DOC extract immune spleen cells were added to a mixture of KMT-17 cells and KMT-17 immune spleen cells. This suppressive activity of the spleen cells was diminished by the treatment with anti T serum and complement. After fractionation of DOC extract immune spleen cells by the Ficoll density gradient, the cells in the light layer showed an enhancing effect on tumor growth, whereas the cells in the heavier region of the gradient had an inhibiting effect. These results suggested that both immunosuppressor cells and cytotoxic cells were induced in rats immunized with DOC extract.