A first aspect of the invention relates to the bacterial species Roseburia hominis for use in: regulating the immine system of a subject treating an immune disorder treating an intestinal disorder improving intestinal microbiota regulating the innate immune system of a subject regulating the adaptive immune system of a subject regulating appetite in a subject promoting Tregs and immune tolerance promoting gut health in a subject and/or maintaining immune homeostasis in a subject. Further aspects of the invention relate to compositions comprising Roseburia hominis.