Lung tissue-resident memory T cells optimize protection by IL-10 regulation of innate immunity

Respiratory viral infections establish tissue resident memory T (TRM) cells in the lung, which provide optimal protection against infectious challenge, though the underlying mechanisms remain incompletely understood. Here, using a mouse model of heterosubtypic influenza infection, we demonstrate that the lung-localized secondary immune response exhibits an attenuated innate immune response compared to the primary response due to TRM-mediated production of the immunoregulatory cytokine IL-10. Using reporter mice, we identify that lung TRM are the predominant producers of early IL-10 in response to viral challenge. Inhibition of early IL-10 signaling in secondary infections results in increased morbidity and lung pathology, and reveals pleiotropic effects of IL-10 in regulating macrophage inflammation and enhancing IFN-g production by memory CD8+T cells. Human influenza-specific TRM isolated from lungs recapitulate robust IL-10 expression associated with augmented effector responses of murine TRM. These data support a dual role for TRM in coordinating in situ secondary responses - augmenting effector responses for robust viral clearance while dampening inflammation to limit tissue damage. Overall design: There are two experiments of data submitted here. The goals of these experiments were to determine the effect of either (1) previous infection or (2) IL-10 signaling blockade on the lung-localized immune response to subsequent viral infection. To study this, we prepared RNA from whole lung homogenate of mouse lungs undergoing respiratory infection (IAV). For experiment (1), we compared mice undergoing either primary infection or secondary infection. Mice undergoing primary infection are defined as naive mice that are seeing IAV (PR8) for the first time. For secondary infection, we primed mice by infection of one strain of IAV (X31), waited 5 weeks for recovery, and then infected them with PR8 at the same time as mice undergoing primary infection. Lungs were harvested at days 1, 2, and 3 post-infection. Uninfected mice at baseline were also prepared as controls. For experiment (2), we wanted to determine the effects of IL-10 signaling in secondary infections. For these, we prepared memory mice as previously described, and then simultaneously administed an IL-10R blocking antibody at the time of infection. Lungs were collected at 2 days post infection, and uninfected mice were used as control.