Immunity to the T1699 murine mammary tumor. I. Thymic influence and long-term effect of irradiation on the humoral response.

The thymus dependency of humoral immunity to syngeneic tumor antigens was investigated in T cell-deficient DBA/2 mice. ATXBM animals bearing the T1699 mammary tumor in the subcutaneous abdominal area displayed normal immediate but not delayed hypersensitivity reactions (DHR) to 3 M KCl-extracted T1699 antigens injected into the footpad. Sera from ATXBM tumor-bearers passively transferred immediate hypersensitivity but failed to support tumor-specific macrophage-mediated ADCC reactions. The synthesis of macrophage-mediated ADCC antibody was greatly reduced in the CXBM animals when compared to nonirradiated tumor-bearers. The CXBM mice, however, showed normal T cell function as measured by allograft rejection, antibody response to sheep erythrocytes, and DHR to T1699 antigens. Of all antibody classes and subclasses tested by indirect membrane fluorescence, only IgG2b was found to be produced at normal levels by either ATXBM or CXBM tumor-bearers. The results show that IgG2b antibody production in response to T1699 syngeneic tumor antigens is thymus independent and suggest that this antibody is the mediator of immediate hypersensitivity. The synthesis of macrophage-mediated ADCC antibody (IgG2a) was found to be not only thymus dependent but also sensitive to the long-term effects of irradiation and bone marrow repopulation.