makrofaage

Makrofaage are a type of white blood cell that forms part of the body's innate immune system. They are large, phagocytic cells found in almost all tissues and originate mainly from circulating monocytes that migrate into tissues in response to infection or injury. After entering tissues, they differentiate into resident macrophages with specialized functions, such as alveolar macrophages in the lung, Kupffer cells in the liver, microglia in the brain, and osteoclasts in bone.

Key roles include engulfing and destroying pathogens and cellular debris, clearing apoptotic cells (efferocytosis), and presenting antigens to T cells through MHC class II molecules. Macrophages express a range of pattern recognition receptors, such as Toll-like receptors and scavenger receptors, enabling detection of microbes and damaged cells. They secrete cytokines and chemokines that regulate inflammation and recruit other immune cells.

Macrophages can adopt different functional states in response to signals from their environment. Classical (often called M1) activation, driven by IFN-γ and microbial products, promotes antimicrobial and pro-inflammatory activities. Alternative (often called M2) activation, driven by IL-4 and IL-13, supports tissue repair and anti-inflammatory responses. In practice, macrophages exist on a spectrum rather than in strict categories. Dysregulated macrophage activity is implicated in diseases such as chronic inflammation, atherosclerosis, and cancer, where tumor-associated macrophages can influence tumor growth and metastasis.