A direct and nonredundant role for thymic stromal lymphopoietin on antiviral CD8 T cell responses in the respiratory mucosa.

Mucosally produced thymic stromal lymphopoietin (TSLP) regulates Th2 responses by signaling to dendritic cells and CD4 T cells. Activated CD8 T cells express the TSLP receptor (TSLPR), yet a direct role for TSLP in CD8 T cell immunity in the mucosa has not been described. Because TSLP shares signaling components with IL-7, a cytokine important for the development and survival of memory CD8 T cells in systemic infection models, we hypothesized that TSLP spatially and nonredundantly supports the development of these cells in the respiratory tract. In this study, we demonstrate that influenza infection induces the early expression of TSLP by lung epithelial cells with multiple consequences. The global loss of TSLP responsiveness in TSLPR(-/-) mice enhanced morbidity and delayed viral clearance. Using a competitive adoptive transfer system, we demonstrate that selective loss of TSLPR signaling on antiviral CD8 T cells decreases their accumulation specifically in the respiratory tract as early as day 8 after infection, primarily due to a proliferation deficiency. Importantly, the subsequent persistence of memory cells derived from this pool was also qualitatively and quantitatively affected. In this regard, the local support of antiviral CD8 T cells by TSLP is well suited to the mucosa, where responses must be tempered to prevent excessive inflammation. Taken together, these data suggest that TSLP uniquely participates in local immunity in the respiratory tract and modulation of TSLP levels may promote long-term CD8 T cell immunity in the mucosa when other prosurvival signals are limiting.