CD28 expression on peripheral blood T lymphocytes after orthotopic liver transplant: upregulation in acute rejection.

Despite immunosuppressive treatments, acute rejection remains a significant cause of graft loss. Efficient allorecognition implicates cognate T-cell 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 allograft acute rejection. Fifty-five CsA-immunosuppressed orthotopic liver recipients, with or without acute rejection (AR and NAR) were immunocytometrically monitored after transplant and thirty healthy volunteers were studied as controls. In liver recipients the absolute number of CD28+ cells fell sharply immediately after transplant, but no significant differences were detected between the AR and NAR groups either in the absolute number or in the percentage of CD28+ lymphocytes. By contrast, both CD4+CD28+ and CD8+CD28+ T-cell subsets displayed a significant increase in CD28 intensity expression in AR recipients, whereas CD28 expression was significantly downregulated in the NAR recipients. This data suggests that CD28 molecule can be important in the immunologic events preceding acute rejection and that CD28 up- or downregulation could become a useful predictive marker for acute rejection or tolerance development in liver recipients.