LAUSR

Commensal microbes colonize mucosal surfaces throughout the body, but whether there is a resident population of microbes present on the ocular surface has been controversial. In Immunity, Caspi and colleagues establish that Cornyebacterium mastitidis is a de facto resident microbe present on mouse conjunctiva that ‘tunes’ the local immune response. Several other bacteria tested, including other Cornyebacterium species and Staphylococcus epidermidis, fail to colonize the conjunctiva after inoculation. The presence of C. mastitidis results mainly in the activation and population expansion of ocular IL-17A+ gδ T cells, which in turn supports the induction of anti-microbial peptides and the recruitment of neutrophils to the conjunctiva. Mice lacking C. mastitidis have fewer conjunctival IL-17A+ gδ T cells and greater vulnerability to infection of the eye with Candida albicans or Pseudomonas aeruginosa. C. mastitidis is therefore a specialized commensal resident in the conjunctiva that can mediate localized protection through the induction of IL-17A production. ZF Immunity 47, 148–159 (2017) Dopamine in germinal centers Follicular helper T cell (TFH cell)–B cell interactions in germinal centers lead to the generation of long-lived plasma cells that produce high-affinity antibodies. In Nature, Papa et al. show that human TFH cells express enzymes necessary for production of the neurotransmitter dopamine, which is released after cognate interactions with follicular B cells that express the dopamine receptor DRD1. This bidirectional interaction leads to upregulation of surface expression of the ligands ICOS-L on B cells and CD40L on TFH cells, which enhances the formation of T cell–B cell synapses. Curiously, mouse follicular lymphocytes do not display similar dopamine-dependent signaling interactions. Simulation experiments suggest that dopamine signaling might speed germinal-center interactions and enhance plasma-cell generation. Testing of this hypothesis, however, awaits the development of in vivo models. LAD Nature 547, 318–323 (2017)