Generation of Regulatory Dendritic Cells by Administration of Donor Alloantigen in Mouse Transplantation Model.

Backgrounds: Various lines of evidence indicate that regulatory cells control peripheral immune responses in self-tolerance and transplantation. Here we show that administration of donor alloantigen via the trachea generated not only CD4⁺ regulatory cells but also regulatory dendritic cells (DCs) and induced hyporesponsiveness to fully allogeneic grafts in mouse transplantation model.

Methods and Results: CBA mice (H-2^k) received administration of C57BL/10 (B10: H-2^b) splenocytes via the trachea (intratracheal delivery; ITD). Seven days later, the CBA mice underwent transplantation of B10 hearts. Untreated CBA recipients rejected B10 allografts acutely (median survival time [MST], 8 days). ITD of B10 splenocytes induced prolongation of B10 allograft survival in CBA recipients (MST, 67 days). To determine whether regulatory cells were generated by ITD treatment, adoptive transfer study was conducted. Seven days after CBA mice (primary recipients) were given B10 splenocytes by ITD, splenocytes from the primary recipients were adoptively transferred into naive secondary CBA recipients that underwent B10 cardiac grafting the same day. Secondary CBA recipients given not only whole but also CD4⁺ splenocytes from ITD-treated CBA mice (primary recipients) 7 days before had significantly prolonged survival of B10 allografts (MST, 78 and 68 days, respectively, compared to those in control secondary CBA recipients with adoptive transfer of naive whole or CD4⁺ splenocytes, MST, 11 and 13 days, respectively). Interestingly, adoptive transfer of CD11c⁺ cells from ITD-treated CBA mice also induced prolongation of B10 allograft survival in naïve secondary recipients (MST, 85 days, compared to that in control secondary recipients with adoptive transfer of naive CD11c⁺ cells, MST, 9 days). These CD11c⁺ cells produced interleukin (IL)-10 upon activation. Experiments using anti-IL-10 monoclonal antibody revealed that both induction and effector function of the regulatory cells required IL-10.

Conclusion: Our data indicate that ITD of donor alloantigen induced hyporesponsiveness to fully allogeneic grafts, and generated regulatory cells that contained both DCs and CD4⁺ cells in our model.