Inflammation in chronic degenerative disorders: A novel CD3+CD56+ subset that regulates CD8+ T cell effector function.

It has been reported that a growing and heterogeneous group of regulatory cell modulate immune response. In particular, regulation of CD8+ T lymphocyte effector functions is critical for tissue homeostasis and immune tolerance control. Here, we report that the co-expression of CD3 and CD56 molecules identify a novel human regulatory T cell population exerting suppressive activity on proliferation, cytotoxicity and IFN-? production of TCR-activated human CD8+ T lymphocytes. Regulatory functions of human circulating CD3+CD56+ T lymphocytes require cell-to-cell contact and are exerted in both autologous and allogeneic conditions. Of note, CD3+CD56+ T cells are reduced and functionally impaired in children affected by Type 1 Diabetes (T1D), at disease onset. Conversely the frequency of this cell subset is increased in patients with prostate cancer. Taken together, our findings reveal that freshly isolated human CD3+CD56+ cells specifically control activation of human CD8+ T lymphocytes. Perturbation of number and function of this cell subset may account for the deranged functions of CD8+ T lymphocytes observed in autoimmune conditions, including T1D. Thus, therapeutic manipulation of CD3+CD56+ cells may represent an innovative approach to restore immune function in T1D.