Murine melanoma-specific tumor rejection activity elicited by a purified, melanoma-associated antigen

B700 is a melanoma-specific glycoprotein antigen, with a m.w. of 65,000 and an isoelectric point of 4.5; this antigen has been shown to bear significant sequence homology to a normally occurring protein, serum albumin. The production of B700 is apparently restricted to all the murine melanomas tested, since a variety of other transformed and untransformed cell lines do not contain detectable levels of this antigen. The capacity of B700 to function as a tumor-specific transplantation antigen (TSTA) is demonstrated in this study. This activity has been titrated, and it is shown that mice immunized with B700 are able to significantly inhibit the growth of B16 F₁₀ melanomas after subcutaneous challenge; immunized mice can also inhibit the establishment and growth of experimental metastases in the lungs after i.v. challenge with B16 melanoma cells. The TSTA was found to cross-protect also against challenge with two other murine melanoma lines, JB/RH and K1735, but was specific in that the growth of two nonmelanoma lines (RBL-5 leukemia and MCA-105 sarcoma) was not affected. B700 is also shown in this study to be unrelated to other known murine tumor antigens, or to murine leukemia virus antigens. It is further shown that mice immunized with B700 produced antibodies specific to B700 that were not cross-reactive with albumins from various mammalian sources.