Defective inhibition of peripheral CD8+T cell IL-2 production by anti-calcineurin drugs during acute liver allograft rejection

Background. The aim of this study was to evaluate calcineurin activity and interleukin-2 (IL-2) expression by peripheral blood cells as a means of assessing the immune status of liver transplant recipients. Methods. Twenty-one patients were studied in a randomized study comparing cyclosporine and tacrolimus as the main inununosuppressive drug. Calcineurin activity was determined after separation of phosphorylated and dephosphorylated products of a calcineurin specific peptide substrate by high performance liquid chromatography (HPLC). Intracellular IL-2 expression was measured by flow cytometry. In 34 additional patients, intracellular IL-2 expression was prospectively measured. Results. Calcineurin activity fell after transplantation. Values were marginally higher in patients with acute rejection (P=0.059). The percentage of IL-2-producing T cells fell after transplantation. This percentage did not differ between patients with and without rejection. In contrast, the proportion of IL-2-producing CD8+ T cells was higher in patients with acute rejection than in patients free of acute rejection (P=0.003). Moreover, pretransplantation IL-2 expression by CD8+ T cells was higher in patients who subsequently developed acute rejection, suggesting that IL-2 production may be constitutively higher in those patients. The results obtained in the 34 additional patients confirmed these results. Conclusions. These data suggest that quantification of intracellular IL-2 in CD8+ T cells may be a useful index of immune status in liver transplant recipients. Preoperative IL-2 levels might serve to individually tailor the immunosuppressive regimen.