Immunologic responses to a murine mammary adenocarcinoma. I. Passive transfer of immunity by sera from tumor-bearing mice.

DBA/2 mice bearing a syngeneic mammary adenocarcioma T1699 produced high levels of tumor-specific antibody, detected by indirect immunofluorescence and subsequently identified as the IgG2a subclass. Tumor-bearer sera passively administered to normal recipients protected the animals from subsequent challenge with T1699 tumor cells butnot from challenge with a non-cross-reacting syngeneic tumor, SaD2 fibrosarcoma. Administration of sera prior to tumor challenge was found to be more effective than treatment after the challenge. The protective effect of sera appeared to parallel both antibody titers and appearance of concomitant immunity; however, sera absorbed with T1699 cells, with the indirect fluorescent antibody titers reduced more than 100-fold, conferred an almost identical level of protection. Immune suppression of serum recipients before serum transfer abolished the effect, suggesting that protection depended on a cellular immune response by the host in addition to the possible protective effect(s) of humoral antibody.