Influence of donor specific transfusion with impaired ICOS/B7h allorecognition on CD4 + CD25+regulatory T cells of cardiac allograft recipient

Objective To investigate the possibility of CD4+CD25+ regulatory T cells (Treg) enhancement, which induced by donor specific transfusion combined with blockade of ICOS/B7h costimulation following an allogenic murine heterotopic cardiac transplantation. Methods Recipient mice were assigned to 3 groups. In allogenic group, donor hearts were harvested from BALB/C mice, and allografts were heterotopically transplanted in the neck of C57BL/6 using Chen' s technique, without treatment. In isogeneic group, donor hearts were harvested from C57BL/6 mice, and isografts were heterotopically transplanted in the neck of C57BL/6, without treatment. In treatment group, a combination of 5 × 106 ICOS-Fcrecipient C57BL/6 mice following a heterotopic cardiac allograft transplantation. Graft function was assessed daily by palpation, with rejection defined as the absence of detectable beating, then survival of grafts was recorded. CD4 + CD25 + Treg subsets in the peripheral blood of allograft recipients were analyzed by flow cytometry. The expression of FOXP3 mRNA was detected by reverse transcription-polymerase chain reaction (RT-PCR). To assess the suppressive activity of CD4 + CD25 + Treg from tolerant C57BL/6 mice on CD4 + CD25- Teff from naive BALB/C mice, suppression allogeneic MLR assays were performed in vitro.Results In comparison with allogenic group, the survival of cardiac grafts could be prolonged by the comICOS-Fc on the day 0-6 [(84.38 ± 29. 14) days vs (7.00 ± 0. 76) days, P ＜ 0. 01]. Among 3 groups, a considerable proportion of CD4 + CD25 + Treg could be observed in treatment group [(15.60 ± 5.69 )% ,P ＜0. 01], meanwhile, high expression of FOXP3 mRNA was also detected within allografts in treatment group.Furthermore, in contrast to naive C57BL/6 mice, CD4+ CD25 + Treg harvested from tolerant C57BL/6 mice showed more potent suppressive effect on the proliferation of CD4 + CD25 - Teff. Conclusion Allograft tolerance can be induced by donor specific transfusion with impaired ICOS/B7h allorecognition. CD4 + CD25 + Treg played a critical role in the establishment and the maintenance of this allograft tolerance. Key words: Regulatory T cells;  Donor specific transfusion;  Inducible costimulator;  Cardiac allograft tolerance