Immunoelectron microscopic studies of antibodies in mouse sera directed against mouse mammary tumor virus.

Indirect immunoferritin and fixed immunofluorescence tests were carried out on (a) sera of mice hyperimmunized with isologous mouse mammary tumor virus (MMTV) particles or isologous MMTV-producing mammary tumor cells grown in tissue culture and (b) sera of mammary tumor-bearing and tumor-free mice of several inbred strains. Sera were tested against MMTV produced by C3H/HEJ/Tex tissue culture cells (MMT-1). Mammary tumor-bearing A/Dm, C3H/HeTex, and RIII/Dm mice and apparently tumor-free A/Dm mice were found to develop naturally occurring nonprotective anti-MMTV antibodies, whereas sera of tumor-free C3H/HeTex, RIII/Dm, and C57BL/6/Tex female mice and A/Dm, C3H/HeTex, and RIII/Dm male mice did not contain anti-MMTV antibodies. Indirect immunoferritin and fixed immunofluorescence labeling of MMTV particles was prevented by absorbing sera with purified MMTV particles. The results demonstrate the relationship of naturally occurring anti-MMTV antibodies in mouse sera to the presence of mammary tumors, confirm previous reports that mice are not tolerant to MMTV, and further establish the usefulness of the indirect immunoferritin procedure in studies of the immune response of mice.