Background: Spontaneous peritonitis is a rather rare event, even in peritoneal dialysis (PD). As defensins are natural antimicrobial peptides, we hypothesized that adipocytes as the major constituents of the omentum could play an important role in protecting against infection by generating defensin (DEFA1-3). Methods: We isolated adipocytes from the omentum majus and conducted qualitative and quantitative RT-PCR and immunohistochemical analyses. Results: For the first time described, we were able to detect DEFA1-3 mRNA in highly purified isolated omental adipocytes. The expression of DEFA1-3 in adipocytes was confirmed on the protein level by immunohistochemistry. Conclusion: Our report of DEFA1-3 expression by human omental adipocytes adds to the role of adipocytes in the primary defense against bacterial infection. This may include PD, where the presence of the catheter as a foreign body and the nonphysiological dialysis solution may require constant defense measures to prevent peritonitis, a hypothesis that will require further testing. Copyright (C) 2010 S. Karger AG, Basel