The effect of islet cell culture in vitro at 24°C on graft survival and MHC antigen expression

A period of in vitro culture prior to transplantation has been shown to prolong the survival of many types of MHC-incompatible endocrine grafts. The effectiveness of this strategy has been attributed to a selective depletion of intragraft antigen-presenting cells. We report that in vitro culture at 24°C results in a significantly better survival of rat isolated islet allografts than does culture at 37°C. Using in vitro assays of APC activity, we were unable to detect differences in the quantity of residual intraislet APCs between 24°C and 37°C culture preparations. In contrast, islet endocrine cells cultured at 24°C evidenced a reduced level of cell surface class I MHC antigen expression and were significantly less vulnerable to lysis in vitro by CTL. These findings suggest that culture at 24°C produces islet alterations other than APC depletion, and that its beneficial effect on graft survival correlates with a reduction in endocrine cell class I MHC antigen expression.