Antigen-induced but not innate memory CD8 T cells express NKG2D and are recruited to the lung parenchyma upon viral infection

The pool of memory-phenotype CD8 T cells is composed of antigen-induced (AI) and cytokine-induced innate (IN) cells. IN have been described as having similar properties to AI memory cells. However, we found that pathogen-induced AI memory cells can be distinguished from naturally-generated IN memory cells by surface expression of NKG2D. Using this marker, we described the increased functionalities of AI and IN memory CD8 T cells compared to naive cells, as shown by comprehensive analysis of cytokine secretion and gene expression. However, AI differed from IN memory CD8 T cells by their capacity to migrate to the lung parenchyma upon inflammation or infection, a process dependent on their expression of ITGA1/CD49a and ITGA4/CD49d integrins.