PDCD1 and autoimmune disease: However, we found that newly generated PD-1−/− T cells isolated from the periphery of adult animals were indeed capable of generating autoimmune disease (particularly cachexia, kyphosis, and diarrhea) similar to PD-1−/− thymocytes, and much more efficiently than established T cells which contained approximately 1.3% contaminating GFP+ cells (Figure 2A).