PDCD1 and Autoimmunity: The PD1‐PDL1 pathway, a pivotal modulator of T‐cell homeostasis and Tregs development, is critical for limiting the immune response and thwarting the development of autoimmunity.32, 41, 42, 43 Not surprisingly, it has been reported that PD1 is found to be decreased on the surface of PBMCs of ITP patients.39 However, the expression of PD1 on CD4+ T cells in ITP patients has not been reported.