Blimp-1 Rather Than Hobit Drives the Formation of Tissue-Resident Memory CD8 T Cells in the Lungs.

Tissue-resident memory CD8 T (T) cells that develop in the epithelia at portals of pathogen entry are important for improved protection against re-infection. CD8 T cells within the skin and the small intestine are long-lived and maintained independently of circulating memory CD8 T cells. In contrast to CD8 T cells at these sites, CD8 T cells that arise after influenza virus infection within the lungs display high turnover and require constant recruitment from the circulating memory pool for long-term persistence. The distinct characteristics of CD8 T cell maintenance within the lungs may suggest a unique program of transcriptional regulation of influenza-specific CD8 T cells. We have previously demonstrated that the transcription factors Hobit and Blimp-1 are essential for the formation of CD8 T cells across several tissues, including skin, liver, kidneys, and the small intestine. Here, we addressed the roles of Hobit and Blimp-1 in CD8 T cell differentiation in the lungs after influenza infection using mice deficient for these transcription factors. Hobit was not required for the formation of influenza-specific CD8 T cells in the lungs. In contrast, Blimp-1 was essential for the differentiation of lung CD8 T cells and inhibited the differentiation of central memory CD8 T (T) cells. We conclude that Blimp-1 rather than Hobit mediates the formation of CD8 T cells in the lungs, potentially through control of the lineage choice between T and T cells during the differentiation of influenza-specific CD8 T cells.