Role of regulatory T cells in CD47/donor-specific transfusion-induced immune tolerance in skin-heart transplantation mice.

OBJECTIVES

To explore the role of regulatory T (Treg ) cells in the establishment of immune tolerance induced by donor-specific transfusion (DST) in mice with skin-heart transplantation.

METHODS

C57BL/6 mice received DST of splenocytes from CD47+/+ or CD47-/- H-2bm1 mice or no DST 7 days before skin-heart transplantation from major histocompatibility complex class I-mismatched H-2bm1 donors. The number and proportion of Treg cells in graft and lymphoid organs were measured by flow cytometry (FACS) and immunohistochemistry (IHC). The inhibitory function of Treg cells and anti-donor T-cell responses were assessed by mixed lymphocyte reaction.

RESULTS

We observed that mean survival time (MST) of skin or heart graft was significantly longer in C57BL/6 mice which received DST from CD47+/+ H-2bm1 mice than from CD47-/- H-2bm1 mice. By FACS, we found that the number of Treg cells in spleen was increased significantly in mice which received CD47-/- DST compared to mice which received CD47+/+ DST. However, the percentages of Treg cells in total splenocytes and lymph node cells were significantly higher in mice that received CD47+/+ DST than mice which received CD47-/- DST. Immunohistochemistry showed an increased heart grafts infiltration of Treg cells in the recipients with CD47-/- DST, but not CD47+/+ DST. Supporting this, we found that donor T-cell proliferation was significantly suppressed in mice which received CD47+/+ DST compared to mice which received CD47-/- DST. There was no difference of inhibitory function of Treg cells between these two groups.

CONCLUSION

Our results indicated that CD47 expression on DST cells plays an important role in the induction of immune tolerance in mice with skin-heart transplantation. Increased percentage of Treg cells may contribute to immune tolerance induced by CD47+/+ DST.