Abstract： Objectives To study the expression of CTLA4Ig gene in diabetic rat and the action of CTLA4Ig on prolonging survival time of the pancreatic islet.Methods The rat pancreatic islet cells and muscle cells were transfected with the cDNA for CTLA4Ig packaged with lipofectin vector.The expression levels of CTLA4Ig gene and T lymphocyte reaction(MLR)were determined and the action of CTLA4IgcDNA on prolonging survival time of the pancreatic islet allograft in diabetic rats observed.Results T lymphocyte transforming test from peripheral intravenous blood at 7 th day after pancreatic islet transplantationrevealed that cpm in group A and group B were 175.7±98.2,254.4±116.3,respectively,with the difference between the two groups being significant(P＜0.05).At 7th day after pancreatic islet allograft in group A,only 2 out of 10 recipients were serum CTLA4Ig positive with their concentrations being 14 ng/ml and 31 ng/ml respectively. The average time of maintaining blood glucose normal levels in the group A after pancreatic islet allograft,(14.8±12.3)days,was significantly longer than (3.6±5.1)days of the roup B(P＜0.05),The average survival time in the group A.(24.0±10.8)days (the longest time was 45 days), was significantly longer than(11.8±4.8)days(the longest time was 21 days)of the group B (P＜0.01). Conclusions The muscle cells and pancreatic islets of the recipient rats were transfected with CTLA4Ig cDNA packaged with lipofectin.CTLA4Ig cDNA could be expressed in the recipient tissues. The expressed product could obviously prolong the survival time of the pancreatic islet allograft and the recipient rats and partly inhibit the cellular immunity to prevent rejection.