title: A narrow circle of mutual friends.
abstract: Commensal microbiota confers a goldilocks state of alertness to pathogens, yet restrains deleterious inflammation. In this issue of Immunity, Geuking et al. (2011) demonstrate that a minimal bacterial community of the Schaedler flora establishes a balance between pro- and anti-inflammatory T cells in the gut.
authors: Howard Hughes Medical Institute and Immunology Program, Sloan Kettering Institute, New York, NY 10021, USA. rudenska@mskcc.org
authors: Alexander Y
authors: AY
authors: Rudensky
authors: Alexander V
authors: AV
authors: Chervonsky