Thymic damage or engraftment with MHCII−/− donor DCs resulted in reduced generation of tTreg cells in GVHD recipients (98, 99), while engraftment of donor-type DCs increased donor- and host-type thymic tTreg generation in GVHD-free MHC-mismatched or haploidentical mixed chimeras (71, 100, 101). The gene discussed is HLA-C; the disease is graft versus host disease.