Objective:To investigate the effects of superagonistic CD28-specific monoclonal antibody JJ316 (supCD28 MAb) on in vivo proliferation of rat CD4+CD25+Fox P3+ Treg (Treg) cells and on allograft rejection reaction in a rat orthotopic tracheal transplantation model.Methods:Rat orthotopic tracheal transplantation models were divided into two groups in the present study.The experimental group was treated with supCD28 MAb(0.5 mg/rat) via intraperitoneal injection on the day of transplantation.Control group was injected with mIgG (0.5 mg/rat).The proportions of CD4+CD25+ FoxP3+ T cell population in cervical lymph nodes,spleen and peripheral blood monocytes were examined by flow cytometry 5 days after operation.The tracheas were also harvested for histological evaluation.Results:The allografts of the experimental group showed greatly improved airway obliteration,infiltration of inflammatory cells,and respiratory epithelial injury compared with those of the control group.Furthermore,The experimental group had significantly increased CD4+CD25+ FoxP3+ Treg cell population in the lymph nodes,spleen and peripheral blood monocytes compared with those in the supCD28 MAb group (\[5.8±1.2\]% vs \[16.9±4.2\]%,\[14.8±3.6\]%,and \[2.9±0.9\]%,\[3.3±1.3\]% vs \[2.8±1.4\]%,respectively,P<0.05).Conclusion:SupCD28 MAb can attenuate airway inflammation injury after orthotopic tracheal transplantation.