A catch-22: Interleukin-22 and cancer.

Barrier surfaces of multicellular organisms are in constant contact with the environment and infractions to the integrity of epithelial surfaces is likely a frequent event. Interestingly, components of the immune system, that can be activated by environmental compounds such as the microbiota or nutrients, are interspersed among epithelial cells or directly underlie the epithelium. It is now appreciated that immune cells continuously receive and integrate signals from the environment. Curiously, such continuous reception of stimulation does not normally trigger an inflammatory response but mediators produced by immune cells in response to such signals seem to rather promote barrier integrity…

The Transcription Factor T-bet Is Induced by IL-15 and Thymic Agonist Selection and Controls CD8αα+ Intraepithelial Lymphocyte Development

Summary CD8αα + intraepithelial lymphocytes (IELs) are instrumental in maintaining the epithelial barrier in the intestine. Similar to natural killer cells and other innate lymphoid cells, CD8αα + IELs constitutively express the T-box transcription factor T-bet. However, the precise role of T-bet for the differentiation or function of IELs is unknown. Here we show that mice genetically deficient for T-bet lacked both TCRαβ + and TCRγδ + CD8αα + IELs and thus are more susceptible to chemically induced colitis. Although T-bet was induced in thymic IEL precursors (IELPs) as a result of agonist selection and interleukin-15 (IL-15) receptor signaling, it was dispensable for the generation of IEL…

Interferon-λ and interleukin 22 act synergistically for the induction of interferon-stimulated genes and control of rotavirus infection.

The epithelium is the main entry point for many viruses, but the processes that protect barrier surfaces against viral infections are incompletely understood. Here we identified interleukin 22 (IL-22) produced by innate lymphoid cell group 3 (ILC3) as an amplifier of signaling via interferon-λ (IFN-λ), a synergism needed to curtail the replication of rotavirus, the leading cause of childhood gastroenteritis. Cooperation between the receptor for IL-22 and the receptor for IFN-λ, both of which were 'preferentially' expressed by intestinal epithelial cells (IECs), was required for optimal activation of the transcription factor STAT1 and expression of interferon-stimulated genes (ISGs). These d…

Type I interferon (IFN-α/β) represents the key element of the antiviral defense mechanisms against most viruses, however, rotaviruses that infect the gut epithelium, display little sensitivity to type I IFN. Here, we report that the intestinal epithelium is a unique cell compartment in the organism that does not depend on type I IFN in antiviral defenses. Type I IFN was unable to induce antiviral gene expression in intestinal epithelial cells (IEC) that correlated well with low epithelial expression of both chains of the IFN-α/β receptor complex. In stark contrast, IECs strongly responded to IFN-λ on baseline, upon IFN treatment and virus challenge. Commensal microflora was found to establi…