The human lung T cell compartment contains many CD8+ T cells specific for respiratory viruses, suggesting that the lung is protected from recurring respiratory infections by a resident T cell pool. The entry site for respiratory viruses is the epithelium, in which a subset of lung CD8+ T cells expressing CD103 (αE integrin) resides. Here, we determined the specificity and function of CD103+CD8+ T cells in protecting human lung against viral infection. Mononuclear cells were isolated from human blood and lung resection samples. Variable numbers of CD103+CD8+ T cells were retrieved from the lung tissue. Interestingly, expression of CD103 was seen only in lung CD8+ T cells specific for influenza but not in those specific for EBV or CMV. CD103+ and influenza-reactive cells preferentially expressed NKG2A, an inhibitor of CD8+ T cell cytotoxic function. In contrast to CD103–CD8+ T cells, most CD103+CD8+ cells did not contain perforin or granzyme B. However, they could quickly upregulate these cytotoxic mediators when exposed to a type I IFN milieu or via contact with their specific antigen. This mechanism may provide a rapid and efficient response to influenza infection, without inducing cytotoxic damage to the delicate epithelial barrier.
Berber Piet, Godelieve J. de Bree, Barbara S. Smids-Dierdorp, Chris M. van der Loos, Ester B.M. Remmerswaal, Jan H. von der Thüsen, Jan M.W. van Haarst, Jan P. Eerenberg, Anja ten Brinke, Wim van der Bij, Wim Timens, René A.W. van Lier, René E. Jonkers
CD8+CD103+ lung T cells have a low cytotoxic potential and a high expression of the inhibitory NK cell receptor complex CD94/NKG2A.