Double negative (CD3⁺4^-8^-) TCRαβ splenic cells from young NOD mice provide long-lasting protection against type 1 diabetes

Background: Double negative CD3⁺4^-- TCRαβ splenic cells (DNCD3) can suppress the immune responses to alio and xenografts, infectious agents, tumors, and some autoimmune disorders. However, little is known about their role in autoimmune diabetes, a disease characterized by the reduction of insulin production subsequent to destruction of pancreatic β-cells by a polyclonal population of self-reactive T-cells. Herein, we analyzed the function and phenotype of DNCD3 splenic cells in young NOD mice predisposed to several autoimmune disorders among which, the human-like autoimmune diabetes. Methodology/Principal Findings: DNCD3 splenic cells from young NOD mice (1) provided long-lasting protection against diabetes transfer in NOD/Scid immunodeficient mice, (2) proliferated and differentiated in the spleen and pancreas of NOD/ Scid mice and pre-diabetic NOD mice into IL-10-secreting T_R-1 like cells in a Th2-like environment, and (3) their anti-diabetogenic phenotype is CD3⁺(CD4^-CD8^-)CD28⁺CD69⁺CD25^low Foxp3^- iCTLA-4^-TCRαβ⁺ with a predominant Vβ13 gene usage. Conclusions/Significance: These findings delineate a new T regulatory component in autoimmune diabetes apart from that of NKT and CD4+CD25^high Foxp3⁺T-regulatory cells. DNCD3 splenic cells could be potentially manipulated towards the development of autologous cell therapies in autoimmune diabetes.