Anti-hgp75/TRP-1 antibody titers in wild type (129/SvEv) or IFN-gamma receptor deficient (IFN-gammaR-/-) mice. Groups of five mice were immunized with hgp75/TRP-1 weekly for five weeks. Sera were collected one week following the final immunization and used in a B16 cell-based ELISA at serial dilutions to determine titer (last dilution at which absorbance was above background). The horizontal lines represent median titer. Results were confirmed using immunoprecipitation-Western blot assays with serial dilutions of sera.