The Role of Innate Leukocytes during Influenza Virus Infection

Figure 3

Immunoprotection and immunopathology mediated by eosinophils and natural killer (NK) cells during influenza. CCL5 and IL-5 released by IAV-infected airway epithelium mediate eosinophil trafficking into the lungs. Eosinophils undergo piecemeal degranulation and secrete inflammatory cytokines that exert anti-IAV activity. Additionally, IAV-infected eosinophils migrate to draining lymph nodes to present viral antigen to CD8⁺ T cells. Once activated, cytotoxic T cells traffic to the lungs to lyse IAV-infected cells. NK cell recruitment is driven by CCL2, CCL5, CXCL9, CXCL10, and CXCL11 secreted by IAV-infected airway epithelium. Engagement of IAV with NK cell receptor NKp46 activates NK cell effector functions. Perforins, granzyme B, and IFNγ released by NK cell destroy IAV-infected cells while IL-22 aids in the regeneration of damaged epithelium.