Membranous nephropathy (MN) occurs either as recurrent or de novo MN in the kidney allograft. Recurrent MN is most often associated with antibodies to the target antigen M-type phospholipase A2 receptor (PLA2R). 1-3 Most cases of de novo MN are PLA2R-negative and the target antigen in unknown.2 We have previously used the laser microdissection and mass spectrometry (LMD/MS) to search for target antigens in PLA2R-negative MN. In this study, we used LMD/MS to search for the target antigen(s) in de novo MN. Our studies identified target antigen FAT1 in de novo MN when it is associated with concurrent antibody mediated rejection.