Human Regulatory CD8 + T Cells

Administration of a humanized monoclonal anti‐CD3 antibody (mAb) to patients with type 1 diabetes (T1D) increases their C‐peptide responses and the CD8/CD4 ratio. Incubation of human peripheral blood mononuclear cells (PBMC) with mAb in vitro has been shown to induce CD8 + regulatory T cells (Tregs) capable of inhibiting proliferation of CD4 + T cells. We hypothesized that CD8 + Tregs function through secretion of cytokines. To test that possibility, we generated CD8 + Tregs, sorted them by FACS, incubated them with syngeneic CD8‐depleted PBMC in the presence of staphylococcal enterotoxin B (SEB), and measured proliferation of T cells and cytokines. Using neutralizing anti‐cytokine mAbs, we show that the inhibitory effect of CD8 + Tregs could be partially alleviated by anti‐CCL‐4, anti‐TNF, and to a lesser extent anti‐IL2, suggesting that these cytokines contribute to CD8 + Treg function.