Cytokine regulation of the balance between alloindifferent and allospecific suppressor induction in mixed lymphocyte cultures.

The effects of exogenous cytokines on the generation of alloindifferent, MHC-unrestricted suppressive activity early on in mixed lymphocyte culture interactions have been investigated. Interleukin 4 strongly blocked the generation of suppression, whereas IL-1, IL-2, and IL-6 enhanced it to some extent. Tumor necrosis factor-alpha, interferons-alpha and -gamma, granulocyte/macrophage colony-stimulating factor, granulocyte CSF, IL-3 and IL-5, and a number of combinations of these factors were without effect in this system. Insofar as the alloindifferent suppression studied here also inhibited the development of allospecific, MHC restricted suppressive activity later in MLC, reduction by IL-4 of its development may have relevance for the use of this cytokine to facilitate the induction of specific suppressor cell-mediated transplantation tolerance in vivo.