Type I Interferon signaling controls the accumulation and transcriptomes of monocytes in the aged lung.

Aging is paradoxically associated with a deteriorated immune defense (immunosenescence) and increased basal levels of tissue inflammation (inflammaging). The lung is particularly sensitive to the effects of aging. The immune cell mechanisms underlying physiological lung aging remain poorly understood. Here we reveal that aging leads to increased interferon signaling and elevated concentrations of chemokines in the lung, which is associated with infiltration of monocytes into the lung parenchyma. scRNA-seq identified a novel Type-1 interferon signaling dependent monocyte subset (MO-ifn) that upregulated IFNAR1 expression and exhibited greater transcriptomal changes with aging than the other monocytes. Blockade of type-1 interferon signaling by treatment with anti-IFNAR1 neutralizing antibodies rapidly ablated MO-ifn cells. Treatment with anti-IFNAR1 antibodies also reduced airway chemokine concentrations and repressed the accumulation of the overall monocyte population in the parenchyma of the aged lung. Together, our work suggests that physiological aging is associated with increased basal level of airway monocyte infiltration and inflammation in part due to elevated type-1 interferon signaling.