Mononuclear phagocyte system (MPS) (MPS)

The Mononuclear Phagocyte System (MPS), historically known as the Reticuloendothelial System (RES), is a widespread network of highly phagocytic cells—primarily monocytes and macrophages—and the tissues that house them, including the liver (Kupffer cells), spleen, lymph nodes, and bone marrow (StatPearls, 2023). Its primary biological functions involve the clearance of pathogens, cellular debris, and senescent erythrocytes, as well as the processing and presentation of antigens to initiate adaptive immune responses (Wikipedia, 2024). In pharmacology, the MPS is not a single molecular target but a critical physiological system that governs the biodistribution and clearance of nanoparticles, liposomes, and other macromolecular drug delivery systems (Journal of Controlled Release, 2016). While it often acts as a sink that limits drug half-life, it is specifically targeted by diagnostic agents like Technetium Tc 99m Tilmanocept, which binds to mannose receptors on RES macrophages for lymphatic mapping (FDA, 2013). Dysregulation of the MPS is implicated in various pathologies, including lysosomal storage disorders, such as Gaucher disease, and plays significant roles in chronic inflammation and the facilitation of metastatic niches in cancer (Nature Reviews Immunology, 2014).

Other names

Reticuloendothelial systemRESMacrophage systemLymphoreticular systemMononuclear phagocytic system

Drugs interact with this system primarily through phagocytic uptake by resident macrophages or receptor-mediated endocytosis (e.g., mannose receptors), leading to sequestration within lymphatic structures and phagocytic organs like the liver and spleen.