Objective To study the effects of cluster of differentiation 40 ligand immunoglobulin (CD40LIg) modified bone marrow mesenchymal stem cells(MSCs) on the rejection of rat islet xenografts. Methods Islets and infected MSCs which were infected with the recombinant adenoviruses containing CD40LIg gene were transplanted under the left kidney capsule of diabetic rats. The blood sugar and the survival of transplantation rats and grafts were observed after transplantation. The morphological changes of grafts were observed. Expression of CD40LIg and insulin were detected by immunohistochemical staining and cytokines were quantified by ELISA. Results (1) The blood sugar of transplantation rats decreased to normal level on day 2 after transplantation. The average level blood glucose of control group (A)

MSCs group (B)

transfected MSCs group (C) increased on day 7

20

47

after transplantation respectively. (2) The grafts of group A

B and C survived for (9±3.2)

(25±5.3)and (59±7.5) days respectively. There are significant deviation of the grafts survival among group A

B and C(F =6.821

P < 0.05). The survival of transplantation rats were (24±6.8)

(51±7.9)and (95±12.7)days in group A

B and C respectively. The survival of transplantation rats compared each other were same as the survival of grafts (F =6.821

P < 0.05). (3) In group A

Serum IL-2 and TNF-α concentration were elevated to a high level within seven days post-transplantation and significantly increased compared with that pre-transplantation (p＜0.01). In treatment group

serum IL-2 and TNF-α concentration decreased. (4) Hematoxylin-eosin staining of grafts showed islets bolus under the kidney capsule of transplantation rats

no inflammatory cell infiltrate and expression of insulin protein at islets in group B and C. The grafts positively stained for CD40LIg in group C. Conclusion CD40LIg gene modified bone marrow mesenchymal stem cells could prolong the survival time of islet xenografts and inhibit the rejection of islet xenografts.