CD28 EXPRESSION ON PERIPHERAL-BLOOD T-LYMPHOCYTES AFTER ORTHOTOPIC LIVER-TRANSPLANT - UP-REGULATION IN ACUTE REJECTION

Despite immunosuppressive treatments, acute rejection remains a signif icant cause of graft loss. Efficient allorecognition implicates cognat e T-celI interactions and requires costimulatory signals such as those delivered via CD28. Therefore, we have studied CD28 peripheral blood T-cell expression, analyzing its possible implications in liver allogr aft acute rejection. Fifty-five CsA-immunosuppressed orthotopic liver recipients, with or without acute rejection (AR and NAR) were immunocy tometrically monitored after transplant and thirty healthy volunteers were studied as controls. In liver recipients the absolute number of C D28+ cells fell sharply immediately after transplant, but no significa nt differ differences were detected between the AR and NAR groups eith er in the absolute number or in the percentage of CD28+ lymphocytes. B y contrast, both CD4+CD28+ and CD8+CD28+ T-cell subsets displayed a si gnificant increase in CD28 intensity expression in AR recipients, wher eas CD28 expression was significantly downregulated in the NAR recipie nts. This data suggests that CD28 molecule can be important in the imm unologic events preceding acute rejection and that CD28 up- or downreg ulation could become a useful predictive marker for acute rejection or tolerance development in liver recipients. (C) American Society for H istocompatibility and Immunogenetics, 1997.