An epithelial integrin regulates the amplitude of protective lung interferon responses

Integrins facilitate intercellular movement and communication. Unlike the promiscuous activities of many integrins, β6 integrin is restricted to epithelia and partners exclusively with integrin αV to modulate acute lung injury (ALI). Given that ALI is a complication of respiratory infection, we used mice lacking β6 integrin (β6 KO) to probe the role of the epithelial layer in controlling the lung microenvironment during infection. We found β6 KO mice were protected from disease caused by influenza and Sendai virus infections. They were also protected from disease caused by Streptococcus pneumoniae infection alone and after prior influenza virus infection, the co-infection representing an often-lethal condition in humans. Resistance in the absence of epithelial β6 integrin was caused by intrinsic priming of the lung microenvironment by type I interferons through a mechanism involving transforming growth factor-β regulation. Expression of β6 on epithelia suppresses the production of interferons, providing an advantage to the pathogen. Acute inhibition of β6 function may therefore provide a means to improve outcomes in lung microbial infections. We used microarrays to explore the gene expression profiles differentially expressed in resident alveolar macrophage cells from wild-type and β6 integrin knockout mice. Cells were purified by sorting from lung digests. The comparison made was CD11c+, autofluorescent+ cells from wild-type controls to the dominant CD11c+, CD11b+, autofluorescent+ cells in the knockout. Note that conventional CD11c+ alveolar macrophages do not exist in the knockout mice.