Circulating CD4+PD-1+ and CD8+PD-1+ T cells are profoundly decreased at the onset of fulminant type 1 diabetes and are restored by treatment, contrasting with CD4+CD25+FoxP3+ regulatory T cells.

Programed cell death protein-1 (PD-1) is an inhibitory receptor expressed by T cells that downregulates the activation and proliferation of these cells to maintain peripheral self-tolerance. Recent studies reported some cases of new-onset type 1 diabetes (T1D) under anti-PD1 or PDL-1 antibodies. We demonstrated that circulating both CD4+PD-1+ and CD8+PD-1+ T cells were profoundly reduced at the onset of fulminant T1D and were restored by treatment in two patients with fulminant T1D.