Vascular-Resident CD169-Positive Monocytes and Macrophages Control Neutrophil Accumulation in the Kidney with Ischemia-Reperfusion Injury

Monocytes and kidney-resident macrophages are considered to be involved in the pathogenesis of renal ischemia-reperfusion injury (IRI). Several subsets of monocytes and macrophages are localized in the injured tissue, but the pathologic roles of these cells are not fully understood. Here, we show that CD169⁺ monocytes and macrophages have a critical role in preventing excessive inflammation in IRI by downregulating intercellular adhesion molecule-1 (ICAM-1) expression on vascular endothelial cells. Mice depleted of CD169⁺ cells showed enhanced endothelial ICAM-1 expression and developed irreversible renal damage associated with infiltration of a large number of neutrophils. The perivascular localization of CD169⁺ monocytes and macrophages indicated direct interaction with blood vessels, and coculture experiments showed that the direct interaction of CD169⁺ cell-depleted peripheral blood leukocytes augments the expression levels of ICAM-1 on endothelial cells. Notably, the transfer of Ly6C^lo monocytes into CD169⁺ cell-depleted mice rescued the mice from lethal renal injury and normalized renal ICAM-1 expression levels, indicating that the Ly6C^lo subset of CD169⁺ monocytes has a major role in the regulation of inflammation. Our findings highlight the previously unknown role of CD169⁺ monocytes and macrophages in the maintenance of vascular homeostasis and provide new approaches to the treatment of renal IRI.