Differentiation of Phagocytic Monocytes into Lymph Node Dendritic Cells In Vivo

TLDR

To examine whether inflammatory monocytes that ingest subcutaneously injected fluorescent microspheres differentiate and traffic to lymph nodes. The study tracked fluorescent microsphere–laden monocytes injected subcutaneously, monitoring their migration to draining lymph nodes and phenotypic changes. Approximately 25 % of the microsphere‑positive monocytes migrated to the T cell area of draining lymph nodes, where they expressed dendritic‑cell markers and costimulatory molecules, distinct from resident skin DCs, and this transport was >85 % reduced in monocyte‑deficient mice, indicating that a minority of inflammatory monocytes carry phagocytosed particles to lymph nodes and become DCs.

Abstract

We investigated the differentiation and trafficking of inflammatory monocytes that phagocytosed subcutaneously injected fluorescent microspheres. As expected, most of the monocytes became microsphere+ macrophages, which remained in subcutaneous tissue. However, about 25% of latex+ cells migrated to the T cell area of draining lymph nodes, where they expressed dendritic cell (DC)-restricted markers and high levels of costimulatory molecules. Microsphere-transporting cells were distinct from resident skin DCs, and this transport was reduced by more than 85% in monocyte-deficient osteopetrotic mice. Thus, a substantial minority of inflammatory monocytes carry phagocytosed particles to lymph nodes and differentiate into DCs.