IMMUNOLOGICAL STUDIES ON MOUSE MAMMARY TUMORS .2. CHARACTERIZATION OF TUMOR-SPECIFIC ANTIBODIES AGAINST MOUSE MAMMARY TUMORS

After injection of isografted mammary tumor MM2 sensitized with rabbit antiserum, resistance was induced in C3H/He mice after repeated challenges with MM2. The serum taken from these mice was found to be cytotoxic against MM2 cells. The serum also inhibited the outgrowth of transplant of primary tissue culture cells of spontaneous mammary tumor of C3H/He mice. A series of transplanted mammary tumors recently converted into ascitic form in our laboratory (MM3, MM4‐1, MM4‐2, MM4‐3, MM6, MM8, MM9, MM11, MM12 and MM13), and Ehrlich ascites tumor were found to be susceptible to this serum, as tested by trypan blue uptake in vitro. Outgrowth of these tumors was also inhibited when tumor premixed with this serum was injected. No cytotoxic effect was observed against normal mouse mammary gland cells of a C3H/He mouse. Sera obtained from hyperimmunized syngeneic C3H/He mice were able to fix complement with MM2 tumors. They were partially inactivated by heating at 56° C and by treatment with 2‐mercaptoethanol. After gel filtration through Sephadex G‐200, complement fixing and cytotoxic activity were found in both 19S and 7S fractions. The 7S fractions, after DEAE cellulose column chromatography, gave a precipititin line at the IgG position in immunoelectrophoresis. From the above evidence, it is concluded that the target cells of the cytotoxic factors of this serum are primary cultured cells or isografted cells of mammary tumors of C3H/He mice. The cytotoxic factors present in the serum are considered to be antibodies against isografts of mammary tumors in C3H/He mice. Copyright © 1969 Wiley‐Liss, Inc., A Wiley Company