Mechanism of the Immunoregulatory Effect of Cloned t Cells on Proliferation in Mixed Lymphocyte Responses

The mechanism of the suppression of the mixed lymphocyte response (MLR) by Tcell clones derived from the murine AMLR was studied in a system employing. 45 μm membrane chambers to isolate the cellular reactants. The clones effectively suppressed MLR regardless of the MHC haplotype of the reactants in the absence of direct cellular contact, via a soluble factor able to pass through this membrane. Utilizing specific neutralizing antibodies, this factor was shown to be principally TNF alpha, with a contributing effect of gamma interferon. Production of TNF alpha by the cloned T cells was confirmed by direct assay of clone culture supcrnatants.