Citation

Using the lymphocyte sequestering drug FTY720, we show that primary infection with H3N2 IAV strain X31 provides tissue localized heterosubtypic immunity independently of humoral immunity against an H1N1 PR8 IAV strain. Within the lung resident niche, the recall response drives faster CD4+ and CD8+ T cell expansion compared to a primary infection. This rapid T cell expansion resulted from in situ TRM proliferation that was augmented by the migration of peripheral T cells. By tracking a nave T cell population specific for the IAV strain used in secondary challenge, we demonstrate that influenza-specific T cells, including those specific for newly introduced antigens, migrate to the lung niche from the local mediastinal lymph node (medLN) where both CD4+ and CD8+ T cells experience enhanced priming and proliferation. We further show that primary infection fortifies the medLN with persistently increased numbers of T cells as well as both CD103+ and CD103- conventional dendritic cells (cDCs) that are transcriptionally similar to cDCs in an infection nave mouse. By depleting Zbtb46+ cDCs, we determine that cDC fortification is a crucial mechanism for enhanced T cell priming and expansion in the medLN during a recall response.