Treatment of humoral rejection in kidney transplantation

Acute antibody-mediated rejection (acute humoral rejection [AHR]) of organ allografts presents most of the time as severe dysfunction with a high risk of allograft loss. Peritubular capillary complement C4d deposition is diagnostic of AHR in kidney allografts and is associated with circulating donor-specific anti-HLA alloantibodies. Removal of alloantibodies with suppression of antibody production and rejection reversal is now possible. Therapeutic strategies that include combinations of plasmapheresis (or immunoadsorption), mycophenolate mofetil, tacrolimus, and/or intravenous immunoglobulins have been used to successfully treat AHR. The optimal protocol to treat humoral rejection remains to be defined. Anti-CD20 monoclonal antibody therapy (rituximab) aiming at depleting B cells and suppressing antibody production has been used as a rescue therapy in some episodes of refractory humoral rejection. Plasmapheresis and/or intravenous polyclonal immunoglobulin, as well as rituximab, have also been used to successfully “desensitize” selected high-immunologic risk patients who were in anticipation of crossmatch-positive (or ABO-incompatible) kidney transplantation. Recent data suggest that chronic kidney allograft rejection might also be monitored by complement C4d in biopsies. The efficacy and safety of immunosuppressive drugs such as tacrolimus, mycophenolate mofetil (or enteric-coated mycophenolic acid), sirolimus, or everolimus in controlling antidonor humoral responses in patients with chronic allograft dysfunction remains to be studied prospectively. The combination of tacrolimus and mycophenolate mofetil appears to effectively suppress antidonor antibody production. In the near future, the possible role of specific anti–B-cell approaches with drugs, such as rituximab, or possibly of new anti–T-cell activation approaches using selective agents such as belatacept should be assessed to refine the management of chronic allograft dysfunction.