Background: It was recently shown that some strains of mice are capable of rejecting transplants independently of B7 and CD40L signaling and that this rejection is mediated by CD8(+) T cells. LFA-1 is known to be important for CD8(+) T cell activation and cytotoxicity. Therefore, blockade of LFA-1 could be important in overcoming costimulation blockade, CD8(+) T-cell-mediated, resistant rejection. The purpose of this study was to define the effect of combined blockade of the LFA-1 and B7 costimulation pathways on the alloimmune response in mice.
Methods: Allogeneic skin transplantation was performed using BALB/c mice as donors and C57BL/6J wild-type or LFA-1-deficient (CD11a(-/-)) mice as recipients. CTLA4Ig or anti-LFA-1 was administered either as an induction or a prolonged therapy. Mixed lymphocyte reactions were conducted to study the effect of CTLA4Ig on T-cell proliferation in CD11a(-/-) mice.
Results and conclusions: Administration of CTLA4Ig completely inhibits CD11a(-/-) T-cell proliferation in response to alloantigens and significantly improved skin allograft survival in CD11a(-/-) mice. Prolonged treatment of wild-type recipient mice with CTLA4Ig and anti-LFA-1 increased median survival time to 45.5 days compared with 16 days after induction therapy, but it was not sufficient to induce indefinite allograft survival in this model.