The relative ability of cell-free fractions of the transplantable human tumor, H. Ep. # 3, to produce H. Ep. # 3 cytotoxins in rats.

In a recent paper (31) it was reported that cytotoxins for the transplantable human tumor, H.Ep. #3, were detected in the sera and associated with the lymphoid cells of rats immunized with either whole or disintegrated cells of this neo plasm. Such cytotoxins for H.Ep. #3, though pres ent, were less potent in rats immunized with other transplantable human tumors or with normal hu man liver and/or spleen. There was thus an indi cation that some specific as well as general antihuman effect was present. Cytotoxins were not found in the sera or cells from normal rats or asso ciated with kidney, liver, or muscle tissue from immunized hosts. The present paper is concerned with an attempt to localize the substance or substances in the H.Ep. #3 cell that caused a production of the cyto toxins described. The tumor cells were fractionat ed into either four or five separate components by differential centrifugation and the various frac tions employed separately for immunization of normal rats. Sera and lymphoid cells as well as kidney tissue obtained from animals so treated were tested in vitro against a standard suspension of H.Ep. #3 cells incubated at 37° C. for 1 hour. Such test material was then implanted subcutaneously into hosts conditioned with x-radiation and cortisone,1 and any growth obtained was examined and charted. It was learned that neither the nuclei nor mitochondria (fractions I and HA) were po tent antigens for the production of sera or lymph oid cells which were cytotoxic for H.Ep. #3. The