Human T cells developing in porcine hematopoietic chimeras are specifically tolerant to the porcine hematopoietic donor. (A-B) Human Thy/Liv graft cells (□) and recipient spleen cells (▪) were prepared from NOD/SCID-Tg mice that received porcine BM transplants plus human Thy/Liv (A; n = 9) or human Thy/Liv alone (B; n = 4) at week 20 after human Thy/Liv implantation. (C) Spleen cells were prepared from NOD/SCID-Tg mice that received double amount of human Thy/Liv tissues with (pBMT + HuThy/Liv) or without (HuThy/Liv alone) porcine BM transplants at week 25 after human tissue implantation (these are the same mice shown in Figure 2C). Shown are MLR responses (mean ± SE) against the porcine BM transplant donor (donor), third-party pig (3rd-Pig), or third-party human (3rd-Hu). SI indicates stimulation index. *P < .05, **P < .01 compared to the antidonor pig response of the same responder cells.