Acinetobacter species in the skin microbiota protect against allergic sensitization and inflammation

Helsinki, Turku, and Kuopio, FinlandBackground: The human commensal microbiota interacts in acomplex manner with the immune system, and the outcome ofthese interactions might depend on the immune status of thesubject.Objective: Previous studies have suggested a strongallergy-protective effect for Gammaproteobacteria. Here weanalyze the skin microbiota, allergic sensitization (atopy), andimmune function in a cohort of adolescents, as well as theinfluence of Acinetobacter species on immune responses in vitroand in vivo.Methods: The skin microbiota of the study subjects wasidentified by using 16S rRNA sequencing. PBMCs wereanalyzed for baseline and allergen-stimulated mRNAexpression. In invitro assays human monocyte-derived dendriticcells and primary keratinocytes were incubated withAcinetobacter lwoffii. Finally, in in vivo experiments mice wereinjected intradermally with A lwoffii during the sensitizationphase of the asthma protocol, followed by readout ofinflammatory parameters.Results: In healthy subjects, but not in atopic ones, the relativeabundance of Acinetobacter species was associated with theexpression of anti-inflammatory molecules by PBMCs.Moreover, healthy subjects exhibited a robust balance betweenanti-inflammatory and T