Invariant natural killer T(iNKT) cells have the powerful potential to expand regulatory T cells(Tregs), especially when they are presented α-galactosylceramide(aGC) by B cells. We previously reported that a liposomal αGC(lipo-aGC) was preferentially incorporated into B cells rather than dendritic cells, and induced ovalbumin(OVA)-specific Tregs in vivo when administered with OVA. In the current study, we administered lipo-aGC with allogeneic cells, such as bone marrow cells(BMCs) and splenocytes(SPCs), to evaluate whether lipo-aGC regulates allo-immune responses through allo-specific Treg generation.

3Gy-irradiated BALB/c(H2^d) mice were transferred BMCs or SPCs obtained from allogeneic donor(B6; H2^b), and subsequently injected lipo-aGC. To support cell engraftment, 0.5mg anti-CD40L mAb was also injected. Both BMCs and SPCs were engrafted on day7 after transfer. Interestingly, only the BMC-transferred mice showed expansion of highly proliferating Tregs in the spleen on day7, whereas the SPC-transferred mice did not(Fig 1). To evaluate antigen specificity of Tregs, we adoptively transferred H2^d+CD4⁺CD25⁺Tregs isolated from the BMC-transferred mice on day7 into SCID mice that were transplanted skin grafts from B6 and C3H(H2^k) mice simultaneously. Thereafter, naive BALB/c T cells were administered into the SCID mice. Although both B6- and C3H-derived graft survival was prolonged, C3H-derived graft was rejected earlier than that derived from B6, suggesting that the Tregs expanded by lipo-aGC plus BMC-transfer have BM donor-specific suppressive potential. Furthermore, when heart transplant was performed on the next day of BMC-transfer, the mice accepted BM donor-derived heart allograft, whereas they rejected the graft from 3^rd party donor(Fig 2). The SPC-transferred mice rejected heart allograft even though the graft was derived from the same donor. Taken together, we presume that lipo-aGC generates allo-specific Tregs in vivo when co-administrated with allogeneic BMCs.

CITATION INFORMATION: Miyairi S, Hirai T, Okumi M, Ishii Y, Yamazaki K, Tanabe K. iNKT Cell Ligands Administered with Bone Marrow Cells Expand Allo-Specific Regulatory T Cells In Vivo and Establish Transplant Tolerance. Am J Transplant. 2016;16 (suppl 3).

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