The combined effect of drugs and tumor-specific antibodies in protection against a mouse lymphoma.

immunity (Calmette-Guérin bacilli and corynebacteria) (1 1) and even by transfer of lymphoid cells from appropriately preimmunized animals (6). Animals. All mice were bred in our own colony and rabbits for immunization were bought from accredited dealers. The carcinogen-induced lymphoma EL4 is specific for C57BL/6 mice (8) and was maintained by i.p. passage in that strain. Antisera. Groups of rabbits were immunized by 3 iv. injections of 108 EM cells at 10-day intervals and bled 10 days later. This particular schedule had been shown to provide an adequate titer of tumor-specific antibody (4). Sera were heated at 56°for 30 mm and generally had a complement mediated cytotoxic titer for C57BL/6 normal lymph node cells of about 1: 1500. Sera were absorbed with normal mouse spleens until no cytotoxicity remained for normal cells (about 3000 to 5000 spleens/lOO ml), but a small cytotoxic titer for EL4 cells was consistently retained (2). This is, of course, a very extravagant procedure with the sera available at this time.