Objective To explore the effect of α- galactosyleramide( α-GalCer ) on immune reconstitution under acute graft-versus-host disease (aGVHD). Methods BALB/c mice were transplanted wit hallogeneic C57BL/6 bone marrow cells and splenocytes (both 1×10

7

)after receiving lethal total-body irradiation. α-GalCer (100 ug/kg) or vehicle (dimethylsulfoxide) was administered intraperitoneally immediately after transplantation. The effects of α-GalCer on immune reconstitution

proliferation of T cells and B cells

hematopoiesis

and thymic microenvironment were assessed. Results The α-GalCer group exhibited higher percentages of CD3

+

CD4

+

CD8

+

B220

+

CD40

+

and CD86

+

cells compared with the vehicle group . The number of colony forming unit per 1000 CD34

+

cells in the α-GalCer group was higher than in the vehicle group ( P=0.0012).In vitro proliferation assays showed that the α-GalCer group had higher percentages of CD3

+

CD4

+

CD8

+

and B220

+

cells compared with the vehicle group. As for the results of in vivo proliferation assays

the numbers of CD3

+

CD4

+

CD8

+

and B220

+

cells were higher in the α-GalCer group than in the normal group

especially the number of B220

+

cells ( P=0.007).Significant difference was not found in thymocyte count between the α-GalCer group and the vehicle group

nor in the percentages of CD3

+

CD4

+

and CD8

+

cells.Conclusion Administration of α-GalCer after allogeneic bone marrow transplantation may promote immune reconstitution in the presence of aGVHD.