Novelties in diagnostics and therapy of antibody mediated rejection.

Antibody mediated rejection (AMR) is becoming an increasing challenge in renal allotransplantation. AMR is usually associated with profound allograft dysfunction and inferior allograft survival. In the era of refined crossmatch-techniques and improved solid-phase assays, hyperacute rejections in presensitized patients are less common. Majority of AMRs occur due to de novo production of donor specific antibodies. AMR appears to stand for a spectrum of histologic changes paralled with immunohistochemical positivity for C4d along peritubular capillaries. Removal of antibodies with plasmapheresis or immunoadsorption in combination with neutralizing and immunomodulatory intravenous immunoglobulin are therapy standards in majority of transplant centers worldwide. The addition of anti-CD20 (rituximab) with the aim to reduce the number of B-cells may offer advantage in some cases. Apart from donor specific HLA-antibodies, non-HLA antibodies reacting to arterial antigens have been speculated to be responsible for rejections in some patients. More precise definition of antigen targets for non-HLA antibodies is emerging. The analysis of the subtle mechanistic and diagnostic differences among rejection subtypes will help to identify patients at particular risk and improve outcome of AMR.