Effect of Triple Costimulation Blockade on Islet Allograft Survival in Sensitized Mice

Background. Islet allograft rejection in sensitized recipients is difficult to control by costimulation blockade using anti-CD154 and cytotoxic T-lymphocyte antigen-4 immunoglobulin (CTLA4Ig). Because leukocyte function antigen (LFA) 1 is highly expressed on memory T cells, adding an LFA-1 blockade may inhibit memory T-cell activities. We examined the effects on islet allograft survival of triple costimulation blockade in presensitized recipient mice. Methods. C57BL/6 mice were sensitized by transplantation under the kidney capsule or intraperitoneal injection of Balb/c islets. Four weeks after transplantation, sensitization was confirmed by flow-cytometric detection of alloreactive antibodies. Diabetes was induced by a single intravenous injection of streptozotocin. Recipients were transplanted with 200 Balb/c islets under the right kidney capsule. Graft function was assessed by daily blood glucose and body weight records. Transplanted animals were divided into 3 treatment groups: group 1, control antibody; group 2, anti-CD154 and CTLA-4 Ig double therapy; group 3, anti-CD154, CTLA4Ig, and anti LFA-1 triple therapy. Injections were administered every second day from day -2 to day 8. Results. Naive mice rejected islet allografts between days 7 and 29 (mean 16 +/- 6 d; n = 5), sensitized mice in group 1 between days 0 and 14 (mean 7 +/- 5 d; n = 8), in group 2 between days 4 and 16 (mean 8 +/- 4 d; n = 7), and in group 3 between days 4 and 26 (mean 11 +/- 7 d; n = 10). Conclusion. Triple costimulation blockade with anti-CD154, CTLA4Ig, and anti LFA-1 was not sufficient to improve islet allograft survival in sensitized recipients.