In vitro and in vivo cytotoxicity to EL 4 sarcoma in New Zealand mice

The immune response of EL-4 tumor was studied in female NZB/W, BALB/c and CDF₁ mice after both in vivo and in vitro immunization with spleen cells as attackers and ⁵¹Cr labeled EL-4 cells as targets. NZB/W mice demonstrated marked changes with age in the cytotoxic response after both in vivo and in vitro sensitization, whereas the other strains did not. These changes were characterized by hyporesponsiveness at 9 mth of age, and hyperresponsiveness at 6 mth of age, relative to 1 mth of age. Antibody to EL-4 tumor was found in unimmunized NZB/W mice and tended to increase with age. Nevertheless, the cytotoxic antibody response in NZB/W mice after in vivo sensitization was similar at 1 mth and 6 mth of age, but was reduced at 9 mth of age. Nine month old NZB/W mice failed to mount an adequate cytotoxic response and were killed by the tumor whereas 1 and 6 mth old animals mounted cytotoxic responses and survived.