Lymphocyte subsets involved in tumor-activated nonspecific feedback suppression.

Cells from the spleen, lymph nodes, and peritoneum of DBA/2 mice bearing a subcutaneous tumor mediate nonspecific suppression of an in vitro antibody response to sheep red blood cells (SRBC) when cocultured with a normal T-cell subset(s). The spleen cells from the tumor-bearing mouse required for the suppression bear the Lyt 1 and Ala 1 surface markers characteristic of "inducer" T cells and activated cells, respectively. The activity of this cell population is also sensitive to irradiation. The normal T-cell subset which cooperates in the suppression bears the Qa-1 surface antigen which has been associated with suppressor cell precursors in several systems but lacks detectable surface Lyt 1 and 2 markers. Suppression of antibody responses in spleen cell cultures from tumor-bearing mice alone could also be elicited, but only when increased numbers of cells were cultured. These data are consistent with the theory that a tumor-activated, Lyt 1+ T-cell subset has the capacity to nonspecifically suppress immune responses by activating a Qa-1+ subset(s) of T suppressor cells, perhaps via feedback signals.