Suppressor, helper and immunoregulatory T cells in normal human blood as defined by theophylline sensitivity.

Two functionally distinct subpopulations of human T cells, one T suppressor and the other T-helper lymphocytes, were separated from normal donor human peripheral blood and tested for immunoregulatory properties. The separation of these two populations was performed by the aid of theophylline sensitivity as described by Shore et al. [1]. In order to assess the activity of the suppressor and helper T lymphocytes, a local xenogeneic graft-versus-host reaction (GVHR) according to the method of Shohat et al. [13] was used. These studied demonstrated that the theophylline sensitive (TS) T-suppressor cells have a suppressor effect on normal human T cells. They were further found to consist of two cell subsets, one suppressive and radiosensitive and the other radioresistant and having the ability to induce feedback help, a finding which may explain the inverse relationship found between the quantity of TS cells added and the degree of suppression obtained in the GVHR as well as the enhancement of the GVHR obtained after addition of irradiated TS cells to autologous T cells. The theophylline resistant (TR) T cells were found to have a helper action when added to autologous T cells and were radioresistant. Soluble cell-free factors from both TS and TR cells were found to mimic the function of the cells from which they were extracted.