Reticuloendothelial System (RES) Also known as the mononuclear phagocyte system (MPS), the RES is a network of cells and tissues crucial for immune defense, homeostasis, and waste clearance.
Composed primarily of phagocytic cells specialized in engulfing and digesting foreign particles, pathogens, and cellular debris.
Main Cell Types:
1) Monocytes:
Large white blood cells from the bone marrow.
Differentiate into macrophages or dendritic cells in tissues.
2) Macrophages:
Tissue-resident phagocytes derived from monocytes.
Found in liver (Kupffer cells), lungs (alveolar macrophages), brain (microglia), and connective tissues (histiocytes).
Key functions: pathogen engulfment, cytokine release, and immune response coordination.
3) Dendritic Cells:
Antigen-presenting cells originating from monocytes or bone marrow progenitors.
Located in skin, lungs, and gastrointestinal tract.
Crucial for initiating adaptive immune responses by presenting antigens to T cells.
4) Neutrophils:
Abundant white blood cells with phagocytic abilities, mainly involved in innate immunity, especially against bacterial infections.
Not traditionally considered part of the RES.
Functions of the RES:
Immune Defense: Engulfs and destroys pathogens (bacteria, viruses, parasites).
Debris Clearance: Maintains homeostasis by removing damaged cells and waste.
Antigen Presentation: Dendritic cells process and present antigens to T cells, triggering adaptive immunity.
Inflammation Regulation: Modulates inflammation via cytokine production and response.
Iron Recycling: Macrophages, particularly in the spleen, recycle iron from red blood cells.