Functional and Phenotypical Impairment of Polymorphonuclear Cells in Atopic Dermatitis: An Additional Cause for the Known Susceptibility to Infections? [*M.T. Fierro and G. Banche contributed equally to this work]

Abstract BACKGROUND: Atopic dermatitis (AD) patients present an high susceptibility to infections. The phagocytic activity of polymorphonuclear granulocytes (PMNs) is mediated by the interactions between Toll-like receptors (TLRs) and pathogen-associated molecular patterns. OBJECTIVE: To investigate functional activity and phenotype of PMNs in AD patients. METHODs: In vitro PMN phagocytosis and intracellular killing towards Klebsiella pneumoniae were evaluated in 24 AD patients; flow cytometry was applied to analyze PMN phenotype. RESULTS: PMNs from AD patients displayed both reduced phagocytic activity and intracellular killing against K. pneumoniae than healthy subjects (HS). CD11b, CD66b, TLR2, TLR4 and TLR5 median fluorescence intensity (MFI) on PMN membrane were significantly higher in AD patients than in HS.CONCLUSION:PMN functional impairment in AD patients could represent an additional cause of skin infections, coupled with other known defects in the innate immune system. The increased MFI of adhesion molecules and TLRs is rather a consequence of the increased skin barrier permeability to bacterial molecules capable of stimulating immunological reactions.