Re-examination of renal allograft biopsy blocks for C4d positivity: missed cases of antibody mediated rejection.

Introduction: C4d immunostaining of renal allograft biopsies is recommended for the diagnosis of antibody-mediated rejection (ABMR), but it was not available to us prior to June 2012. In June 2012, we were able to obtain anti-human C4d polyclonal antibody and decided to retrospectively evaluate archived kidney allograft biopsies at our center for C4d deposition.

Methods: Twenty-four paraffin blocks were available for this study.