The Soil Bacterium Methylococcus capsulatus Bath Interacts with Human Dendritic Cells to Modulate Immune Function

The prevalence of inflammatory bowel disease (IBD) has increased in Western countries during the course of the twentieth century, and is evolving to be a global disease. Recently we showed that a bacterial meal of a non-commensal, non-pathogenic methanotrophic soil bacterium, Bath prevents experimentally induced colitis in a murine model of IBD. The mechanism behind the effect has this far not been identified. Here, for the first time we show that , a soil bacterium adheres specifically to human dendritic cells, influencing DC maturation, cytokine production, and subsequent T cell activation, proliferation and differentiation. We characterize the immune modulatory properties of and compare its immunological properties to those of another Gram-negative gammaproteobacterium, the commensal K12, and the immune modulatory Gram-positive probiotic bacterium, GG . induces intermediate phenotypic and functional DC maturation. In a mixed lymphocyte reaction -primed monocyte-derived dendritic cells (MoDCs) enhance T cell expression of CD25, the γ-chain of the high affinity IL-2 receptor, supports cell proliferation, and induce a T cell cytokine profile different from both K12 and GG. Bath thus interacts specifically with MoDC, affecting MoDC maturation, cytokine profile, and subsequent MoDC directed T cell polarization.