Characterization of the monocyte response in the influenza-infected lungs. (92.12)

Abstract

Abstract Influenza virus infection of the respiratory tract triggers a rapid and vigorous innate immune response. Monocyte/macrophages make up a large fraction of this inflammatory infiltrate and are the major contributors to lung inflammation associated with infection. The monocyte population can be defined as CD11b+Ly6G-Dx5-SiglecF-, and subsets can be further discriminated based on Ly6C expression levels. Here we show rapid accumulation of Ly6Chi monocytes in the infected lungs during the inductive phase of the host immune response, resulting in the predominant if not exclusive accumulation of the Ly6Chi monocyte population at the peak of the inflammatory response. The Ly6Chi monocytes are potent producers of TNF alpha and their presence during early infection strongly correlates with overall lung inflammation. Ly6Chi monocytes slowly decline during the recovery phase following virus clearance, resulting in an accumulation of a Ly6Clo monocyte subset. The presence of this Ly6Clo subset, and the subsequent down-regulation of TNF alpha production in the Ly6Chi subset, strongly correlates with recovery (e.g. weight gain and reduced inflammation) in this mouse model of influenza infection.