Protective immunity by chemically modified tumor cell antigens extracted by 3 M KCl

Tumor antigens from Sarcoma-180 ascites tumor cells were extracted by 3 M KCl before and after treatment with acriflavine. Following dialysis of the extracts against distilled water to remove KCl, the soluble material (antigen) and the precipitate formed during dialysis were collected from the dialysate. Protective immunity of the soluble antigen and the precipitate was evaluated by immunizing mice and subsequent challenge with native tumor cells. It was noted that the soluble antigen and the precipitate of the dialysate obtained from acriflavine-treated tumor cells induced significant protective immunity. The precipitate part appeared to be more effective. Interestingly, similar materials from untreated tumor cells did not show any such protective immunizing efficacy. Antigens extracted by 3 M KCl from chemically modified tumor cells assumed significance in respect to their antitumor immunity.