Natural anti-tumor serum reactivity in BALB/c mice. II. Control by regulator T-cells.

By a complement-dependent cytotoxicity test, 37 sera from 1- to 18-month-old BALB/c mice were tested for natural anti-tumor and anti-thymus immune reactivity. The level of anti-tumor and anti-thymus antibodies increased with age, and a high individual variability, particularly evident in the older animals, was found. The appearance of the spontaneous antibodies was correlated to the T-cell status of mice. Animals with the higher spleen T-cell content were those with the higher anti-thymus and the lower anti-tumor natural antibody level, and vice versa. In T-deprived mice the anti-tumor response increased, whereas the anti-thymus response was not influenced. An inoculum of T cells from young to older syngeneic mice yielded a decrease of the anti-tumor response and an increase of the anti-thymus response. Homeostatic immunologic mechanisms, in which the cellular and the humoral system alternate in the tumor cell control, are suggested.