PDCD1 and autoimmune disease: We previously showed that adult Rag1−/− Kb−/−Db−/− mice were fully permissive for the development of autoimmune disease following transfer of PD-1−/− HSC (24); importantly, no perturbations in the time to disease onset or severity were reported compared to Rag−/− hosts, as would be reasonably expected if the disease were CD8 T cell independent.