DN T cells prolong alloantigen-specific MHC-mismatched skin and islet allograft survival in vivo. (A) DN T cells suppress naive CD4⁺CD25⁻ T-cell–triggered skin allograft rejection in an alloantigen-specific manner. The rejection of skin grafts from DBA/2 or C3H mice transplanted into C57BL/6 RAG⁻/⁻ mice was induced by adoptive transfer of naive C57BL/6 CD4⁺CD25⁻ T cells. Cotransfer of C57BL/6 DN T cells suppressed the rejection more efficiently in mice that received DBA/2 grafts. Statistical analyses were performed using a log-rank test. (B) DN T cells significantly prolonged MHC-mismatched islet allograft survival in an alloantigen-specific manner in immune-competent recipients. Administration of 13 × 10⁶ DN T cells significantly prolonged alloantigen-specific DBA/2, but not third-party C3H, islet allograft survival. Statistical analyses were performed using a log-rank test.