In vitro induction of regulatory T cells by anti-CD3 antibody in humans

Therapy with anti-CD3 antibody is effective in controlling models of autoimmune diseases and can reverse or prevent rejection of grafts. We studied the in vitro immunomodulatory effect of anti-CD3 treated human T cells. CD4(+) T cells were stimulated with plate-bound anti-CD3 and cultured for 12 days after which they were cultured with autologous peripheral blood mononuclear cells (PBMCs) and stimulated with soluble anti-CD3. We found that CD4+ T cells that were stimulated with anti-CD3 (T-alpha CD3) markedly suppressed the proliferation and cytokine production of autologous PBMCs. These regulatory T cells were not induced by incubation with isotype control (T-control) antibody or when anti-CD3 was combined with high doses of anti-CD28 (T-alpha CD3/CD28). T alpha CD3 regulatory cells were anergic and produced lower levels of IFN-gamma, TNF-alpha and IL-2, and higher levels of TGF-beta than T-control or T-aCD3/CD28. There were no differences in the expression of CD25 or CTLA4 on T-alpha CD3 as compared to T-control or T-alpha CD3/CD28, and CD4(+) CD2(5)- T-alpha CD3 cells were identical to CD4(+) CD25(+) T-alpha CD3 cells in their in vitro suppressive properties. Recombinant IL-2 in vitro abrogated the suppressive effect of T-alpha CD3. The suppressive effect was not related to apoptosis, was independent of HLA since T-alpha CD3 also suppressed allogeneic PBMCs, and was not related to soluble factors. Finally, no suppression was observed when non-T cells were removed from culture or when cultures were stimulated with plate-bound anti-CD3, consistent with the ability of T-alpha CD3 to downregulate CD80 on dendritic cells in co-culture experiments. Thus, we have identified human T cells with strong in vitro regulatory properties induced in vitro by anti-CD3 which appear to act in a non-HLA restricted fashion by affecting antigen presenting cells. (C) 2007 Elsevier Ltd. All rights reserved.