RT Journal Article SR Electronic T1 Helicobacter pylori lysate affects the tolerant state of human monocyte-derived dendritic cells JF European Respiratory Journal JO Eur Respir J FD European Respiratory Society SP PA4006 DO 10.1183/13993003.congress-2015.PA4006 VO 46 IS suppl 59 A1 Yolanda Van Wijck A1 Alwin Van der Ham A1 Maria Yazdanbakhsh A1 Pieter Hiemstra A1 Anne Müller A1 Hermelijn Smits A1 Christian Taube YR 2015 UL http://erj.ersjournals.com/content/46/suppl_59/PA4006.abstract AB There is evidence for an interaction of the commensal flora and development of allergic disease. Epidemiological studies and studies in murine models suggest that infection with H. pylori protects against developing allergic airway disease. Treatment with a lysate of the bacteria was also able to reduce allergic airway disease (Engler et al. PNAS 2014). The effect was mediated by IL-10 producing DC, but in contrast to live infection did not depend on the induction of regulatory T cells (Treg). In our in vitro study the effect of lysate of H. pylori on human monocyte-derived (mo-)DC was evaluated. Immature DC exposed for 48 h to H. pylori lysate in presence or absence of LPS matured and strongly increased the release of the anti-inflammatory cytokine IL-10. DCs exposed to the lysate reduced polarization from naïve T cells to Th1 cells. Instead, T cells differentiated by the lysate-exposed DCs of a subgroup of donors secreted more IL-10 compared to T cells from control DC, suggesting the induction of Treg. These Treg were able to suppress proliferation of alloreactive memory T cells in vitro. Our results suggest that H. pylori lysate has strong IL-10 inducing capacities in human mo-DC, which can induce IL-10 secreting T cells with a suppressive function.Further studies are needed to assess if this approach can be utilized in humans to dampen unwanted immune responses.