Production of a tumor-specific xenoantiserum from partially purified immunoprotective tumor antigen

Summary Rabbits imunized with the immunoprotective TSTA fraction partially purified by preparative isoelectric focusing of 3 M KCl extracts from a chemically induced murine sarcoma, MCA-F, produced specific xenoantisera as assessed by an indirect membrane immunofluorescence assay. Only the immunizing tumor, MCA-F, and not the antigenically distinct MCA-D or MCA-T target cells were stained by the xenoantiserum. Absorption of anti-MCA-F antiserum with the antigenically distinct MCA-D or MCA-T cells did not reduce its capacity to bind to MCA-F cells. The immunofluorescence reaction was competitively inhibited by MCA-F fractions that induced specific immunoprotection: crude 3 M KCl extract, isoelectrically focused TSTA (fraction 15), and intact irradiated MCA-F cells. The TSTA specificity of these xenoantisera suggests that they may provide useful reagents for rapid isolation and characterization of the immunoprotective moiety.Abbreviations used: TSTA, tumor-specific transplantation antigens; MCA, 3-methylcholanthrene; MCA-F, MCA-D, MCA-T, methylcholanthrene-induced fibrosarcoma of C3H/HeJ mice; pIEF, preparative isoelectric focusing; PBS, 0.15 M phosphate-buffered saline (pH 7.2); MEM, minimum essential medium; MTD, minimum tumorigenic dose; Fr 15, fraction 15 of pIEF containing TSTA; FI, fluorescence index; FITC, fluorescein isothiocynate