Autogenous antibodies against the murine mammary tumor virus in strains of mice with low incidences of mammary tumors.

The radioimmunoprecipitation assay for the murine mammary tumor virus (MuMTV) was used to detect naturally occurring antibodies against MuMTV in 3 groups of highly inbred mouse strains. 1) Some strains had high incidences of mammary tumors, such as strains GR and C3H. Antibodies against MuMTV were detected in the sera of females of these strains at early ages. 2) Some mouse strains had low incidences of mammary tumors with an intermediate MuMTV expression, such as strains C3Hf, RIIIf, and BALB/c. Some females of these strains developed antibodies against MuMTV. Hormone treatment of these mice resulted in an increase in the proportion of mice carrying antibodies against MuMTV. 3) Some mouse strains were MuMTV-free, such as strains O20, C57BL, and Gr-Mtv2-. No antibodies against MuMTV were detected in the sera of these mice. However, antibodies against MuMTV appeared in the sera of these animals after hormone treatment. The presence of a natural humoral immunity toward MuMTV appeared to be related to the expression of MuMTV in the animals.