The islet resident macrophage is in an inflammatory state and senses microbial products in blood

We examined the transcriptional profiles of macrophages that reside in the islets of Langerhans of NOD, NOD.Rag1-/-, and B6.g7 mice at three weeks of age. Islet macrophages expressed an activation signature with high expression of Tnf, Il1b, and MHC-II both at the transcript and protein levels. These features are common with barrier macrophages of the lung and gastrointestinal tract. Moreover, injection of lipopolysaccharide induced a rapid inflammatory gene expression, indicating that blood stimulants are accessible to the macrophages and that these macrophages can sense them. In NOD mice, the autoimmune process imparted an increased inflammatory signature, including elevated expression of chemokines, chemokine receptors, and an oxidative response. The elevated inflammatory signature indicates that the autoimmune program was active at the time of weaning. Thus, the macrophages of the islets of Langerhans are poised to mount an immune response even at steady state, while the presence of the adaptive immune system elevates their activation state. Overall design: We examined the transcriptional profiles of macrophages that reside in the islets of Langerhans of NOD, NOD.Rag1-/-, and B6.g7 mice at three weeks of age. Lung macrophages and pancreatic LN dendritic cells of NOD mice were also examined.

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Ferris ST, Zakharov PN, Wan X, Calderon B, Artyomov MN, Unanue ER, Carrero JA