d acute exacerbations in chronic obstructive pulmonary disease , little is known about the molecular mechanisms underlying these effects. Bacterial lysates have been empirically, yet extensively, used in the prophylaxis of infections since the beginning of the XX century. The 
rational for this approach was to stimulate an antibody response against pathogens that may protect mucosal surfaces. According to the Activation of Human DC by OM-85 current view of DC biology, orally administered bacterial antigenbased drugs may activate mucosal DC by acting as PRR ligands. In turn, DC would induce antigen-specific T lymphocytes contributing to the isotype switch towards IgA via the secretion of cytokines such as transforming growth factor- b or members of the tumor 14981513 necrosis factor family such as B-cell activating factor and a proliferation-inducing ligand . After maturation, IgA-producing plasmablasts get into the blood stream and preferentially home to mucosalassociated lymphoid tissues of different organs including the airways. Consistent with this view, the protective effect of OM85 in a model of type I diabetes was found to depend on the presence of TGF-b, while human studies indicated that OM85 increased the content of secretory IgA in bronchoalveolar lavage fluid. In addition, several works indicated that OM-85 may act on DC, but the mechanisms underlying this interaction and its biological outcomes have never been investigated thoroughly. Aim of the present research was to systematically investigate the activation properties of OM-85 on human DC subsets. Here, we report that OM-85 activates human DC via the NF-kB and MAPK pathways. This results in a mild pro-inflammatory activation of DC that release selected cytokines and chemokines, which in turn may favor the recruitment of innate effector cells to epithelial surfaces and promote lymphocyte function. This effect is increased by the presence of suboptimal concentrations of proinflammatory stimuli mimicking a pre-existing, subclinical bacterial colonization. IFNc, PDC were stimulated with 2 mg/ml CpG 2116 or OM-85 in the presence of 20 ng/ml IL-3. Polymorphonuclear Neutrophils were isolated after Ficoll and 4% Dextran gradient separation. To lyse red blood cells, collected neutrophils were treated with 0.2% NaCl and 1.2% NaCl. Highly purified blood PMN were obtained by using “Human Neutrophil Enrichment Kit”and “Purple EasySep Magnet” according to the manufacturer’s instructions. THP-1 were purchased from American Type Culture Collection and were cultured in RPMI 1640 complemented with 10% FCS. Cytoplasmic and nuclear extracts preparation Cytoplasmic proteins were separated in L1 buffer with inhibitors. Nuclear pellets were washed twice with L1 buffer with inhibitors and then lysed in NP-40 Lysis buffer with inhibitors. Quantification of protein content was performed by Bradford method according to PF-562271 web standard protocols. Western Blot Equal amounts of cytoplasmatic or nuclear extracts were boiled for 5 minutes in a loading buffer containing 5% glycerol, 0.001% bromophenol blue, 4.5% SDS and 10% 2-mercaptoethanol. Samples were run through 612% polyacrylamide gel and electrophoretically transferred to PDVF membrane. After blocking of aspecific binding, membranes were 10485587 incubated with the indicated primary antibodies for 1 hour at room temperature and then incubated with peroxidase-conjugated secondary antibody for 45 minutes at room temperature. Super SignalH West Pico Chemiluminescent Substrate