CD169 macrophages regulate immune responses toward particulate materials in the circulating fluid

Tissue macrophages comprise heterogeneous subsets that differ in localization, phenotype and ontogeny. They acquire tissue-specific phenotype in order to maintain normal tissue physiology. This review summarizes the current knowledge about the functions of CD169-positive macrophage subset residing in the lymphoid organs and intestinal tract. Strategically positioned at the interface between tissue and circulating fluid, CD169+ macrophages in the lymphoid organs capture blood- and lymph-borne particulate materials. Antigen information relayed by CD169+ macrophages to neighbouring immune cells is important for enhancement of antimicrobial and antitumour immunity as well as induction of tolerance. In the intestinal tract, CD169+ macrophages localize distantly from epithelial border. Following mucosal injury, they exacerbate inflammation by producing CCL8 that recruits inflammatory monocytes. As such, a better understanding of CD169+ macrophage phenotypes may enable the design of tissue-specific therapies for both immunological and non-immunological diseases.