Presentation by donor and host nonhematopoietic APCs. (A) Experimental schema: B6♂ animals underwent thymectomy and were used for generation of (class II^−/−♀→B6♂) chimeras. Three months later, these chimeras were irradiated and transplanted with either B6 or Marilyn T cells and monitored for (B) survival. Data are from 2 combined experiments. (C) Donor APCs alone stimulate GVH responses. Experimental schema: TCD BM from either WT or class II^−/− B6♀ were transplanted along with WT or Marilyn T cells into lethally irradiated BALB/c males. (D) Total donor H2Kd⁺CD4⁺ T-cell expansion, H2kd⁺CD4⁺IFN-γ⁺ T-cell number, and serum IFN-γ concentration from day 7. Data are from 1 of 2 similar experiments. (E-I) Induction of GVHD in the absence of donor and radiosensitive host hematopoietic-derived APCs. (E) Experimental schema: B6Ly5.2 female and male animals were lethally irradiated, treated with anti–natural killer (NK) Ab and transplanted with either WT B6 or β2m^−/− BM. Three months later, these chimeras were transplanted with TCD BM from either WT or β2m^−/− B6♀ animals along with MataHari T cells. The animals were monitored for (F) survival and (G) clinical score. Data from 1 of 3 similar experiments are shown. (H) Donor CD45.2⁺CD8⁺ T cells expansion in spleen and (I) histopathology scores of liver and GI tract. Data from 1 of 2 similar experiments are shown.