Impact of maintenance immunosuppressive regimens--balance between graft protective suppression of immune functions and a near physiological immune response.

The Symphony study showed superior 1-year kidney graft outcome in patients on immunosuppression with tacrolimus/mycophenolate mofetil (Tacr/MMF). To analyze whether differences in clinical outcome between maintenance regimens may be explained by their impact on clinically relevant immune parameters, we assessed CD4 helper activity, immunoglobulin-secreting cell (ISC) formation, neopterin, sCD30, and intracellular cytokine production in a prospective study in 77 renal transplant recipients treated with cyclosporine A/azathioprine (CsA/Aza), CsA/MMF, Tacr/Aza or Tacr/MMF at 2 years post-transplant. Tacr- compared with CsA-based immunosuppression was independently associated with increased IL-2 (P<0.0001, CD4 cells; P=0.014, CD8 cells) and CD4 cell IL-4 responses (P=0.046; stepwise logistic regression) resulting in physiological responses in Tacr/Aza patients as compared with 25 healthy controls. MMF versus Aza treatment was proven to be an independent variable associated with suppression of CD4 cell IL-10 responses (P=0.008), B-cell IL-6R expression (P<0.0001) and ISC formation [P=0.020, staphylococcus cowan strain I (SAC I); P=0.021, pokeweed mitogen (PWM)]. Our data suggest that Tacr/MMF had the most effective impact on graft protective Th2 responses (enhanced CD4 cell IL-4 by Tacr, decreased CD4 cell IL-10 responses by MMF) and suppression of B-cell functions (MMF), whereas Tacr/Aza was associated with physiological IL-2 and IL-4 and stronger humoral responses which may reduce the risk of infectious disease complications.

ATG induction therapy: long-term effects on Th1 but not on Th2 responses.

Antithymocyte globulin (ATG) induction therapy is associated with an increased long-term risk of infection- and cancer-related death. To analyze long-term effects of ATG induction on lymphocyte function, we prospectively assessed CD4 helper function, B-cell/monocyte and cytokine responses in 84 renal transplant recipients (ATG, n = 44) up to 1 year post-transplant. A PWM-driven allogeneic coculture system was used to assess helper function of CD4+ T cells and T-cell-dependent B-cell responses. SAC I was used for T-cell-independent stimulation of B-cell cultures. In vitro cytokine secretion and serum soluble CD30 (sCD30) were determined by enzyme-linked immunosorbent assay (ELISA). ATG induced a persistent decrease of peripheral blood lymphocyte counts compared with non-ATG treatment because of a predominant decrease of CD4+ T cells (4 months, 1 year; P < 0.0005) which was associated with a decreased CD28 expression (1 year, P = 0.02) and CD4 cell interleukin 2 (IL-2) response (4 months, P < 0.0005). However, Th2 responses (CD4 help, CD4 cell IL-4 and IL-10 responses, sCD30), which proved to be predictive of graft outcome, were not affected, and neither was the secretion of the lymphoma growth factors IL-6 and IL-10 by B cells and monocytes. Our data show that ATG induction therapy in immunological high-risk patients induces a profound long-term decrease in cell counts and Th1 but not Th2 responses of CD4+ T cells which may explain long-term effects on infection and post-transplant lymphoproliferative disease (PTLD) incidence because of inadequate T-cell control.