Late acute rejection occurring in liver allograft recipients.

To study the effect of immunosuppressive reduction on the incidence and consequence of late acute rejection (LAR) in liver allograft recipients, mean daily prednisone dose, mean cyclosporine A (CsA) trough and nadir levels were retrospectively reviewed for the nearest 12-week period preceding six episodes of LAR in five liver allograft recipients (group 1). Results were compared with those from a cohort of 12 liver allograft recipients who did not develop LAR (group 2). LAR was defined as acute rejection occurring more than 365 days post-transplantation. Median follow-up for both groups was similar (504 days, range 367 to 1050, versus 511 days, range 365 to 666, not significant). Mean trough CsA levels were lower in patients with LAR compared with those without (224 +/- 66 ng/mL versus 233 +/- 49 ng/mL) but the difference was not statistically significant. In contrast, mean daily prednisone dose (2.5 +/- 1.6 mg/day versus 6.5 +/- 2.9 mg/day, P = 0.007) and CsA nadir values (129 +/- 60 ng/mL versus 186 +/- 40 ng/mL, P = 0.03) were significantly lower in patients who developed LAR compared with those who did not. Five of six episodes (83%) of LAR occurred in patients receiving less than 5 mg/day of prednisone, versus a single LAR episode in only one of 12 patients (8%) receiving prednisone 5 mg/day or more (P = 0.004). In all but one instance, LAR responded to pulse methylprednisolone without discernible affect on long term graft function. The authors conclude that liver allograft recipients remain vulnerable to acute rejection beyond the first post-transplant year; and reduction of immunosuppressive therapy, particularly prednisone, below a critical, albeit low dose, threshold increases the risk of LAR.