ORIGINAL ARTICLE EXPERIMENTAL ALLERGY AND IMMUNOLOGY The allergy-protective properties of Acinetobacter lwoffii F78 are imparted by its lipopolysaccharide J. Debarry 1 , A. Hanuszkiewicz 2 , K. Stein 1 , O. Holst 2 & H. Heine 1 Divisions of 1 Innate Immunity and 2 Structural Biochemistry, Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Borstel, Germany To cite this article: Debarry J, Hanuszkiewicz A, Stein K, Holst O, Heine H. The allergy-protective properties of Acinetobacter lwoffii F78 are imparted by its lipopolysaccharide. Allergy 2010; 65: 690–697. According to the World Health Organization, asthma is one of the most prominent chronic infections in children world- wide, and, moreover, a strong increase in the incidence of asthma and allergies in the last few decades was reported (1). In contrast, the incidence of infectious diseases like mumps, measles, tuberculosis, or hepatitis A is decreased (2). These findings led to the hygiene hypothesis which states that the tremendous increase in atopic diseases corre- lates with less contact to microbes and fewer infections in childhood (3). In this context, a number of epidemiological studies showed that children who grow up in a farming environment will develop less atopic disorders later in life (4–7). This positive effect of the farming environment is cur- rently discussed as a result of the activation of the innate immune system by microbial compounds (8). For instance, an inverse correlation between the microbial burden [mea- sured by the content of lipopolysaccharide (LPS) or CpG motifs] and the development of atopic disorders in children could be shown (9, 10). Furthermore, LPS and CpG motifs seem to be potent in preventing an allergic outcome in mouse allergy models (11, 12). As it is known that the immune response of newborns is T Helper 2 (T H 2) dominated and the first year of life is important for the establishment of a normal T H 1/T H 2/T reg (regulatory T cells) balance (13, 14), it seems plausible that the stimulation of the innate immune system plays an important role in this process by suppressing the allergy- associated T H 2 response by inducing either a regulatory response (T reg ) or a T H 1 immune response. Indeed, at pres- ent, both explanations (lack of immune deviation and lack of immune suppression) are discussed and also supported by a number of studies (15, 16). Both models have in Keywords Acinetobacter lwoffii; allergy protection; hygiene hypothesis; immune deviation. Correspondence PD Dr H. Heine, Division of Innate Immunity, Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Parkallee 22, D-23845 Borstel, Germany. Accepted for publication 30 September 2009 DOI:10.1111/j.1398-9995.2009.02253.x Editor: Thomas Bieber Abstract Background: An increasing number of epidemiological studies show that exposure to farming environment during early childhood strongly influences the development of allergic reactions later in life (‘hygiene hypothesis’). Also, it had been shown that certain bacteria from this environment may have allergy-protective properties. In the present study, we further characterized one of these bacteria, namely Acinetobac- ter lwoffii F78, with regard to the bacteria-induced signaling and possible mecha- nisms of allergy protection. Methods: The impact of A. lwoffii F78 on human monocyte-derived dendritic cells especially with respect to their T Helper cell polarization capacity was investigated by ELISA and real-time PCR experiments as well as confocal microscopy. The respon- sible molecule for these effects was further characterized and identified using block- ing experiments. Results: It was shown that A. lwoffii F78 induced a T H 1-polarizing program in human dendritic cells which led to T H 1 differentiation. In addition, a positive influ- ence on the TBet/GATA3 level could be detected. Blocking experiments revealed that the lipopolysaccharide (LPS) of A. lwoffii F78 was the responsible molecule promoting these effects. Conclusion: We found evidence that the allergy-protecting effects of A. lwoffii F78 are because of the activation of a T H 1-polarizing program in human dendritic cells, and that the LPS of A. lwoffii F78 is responsible for these beneficial effects. Allergy 690 Allergy 65 (2010) 690–697 ª 2009 John Wiley & Sons A/S