makrofaj

Makrofaj, or macrophages, are large phagocytic cells of the immune system. They are key players in the innate immune response and are found in virtually all body tissues as tissue-resident macrophages. They originate from hematopoietic stem cells in the bone marrow, with circulating monocytes that can differentiate into macrophages upon entering tissues. Some tissue macrophage populations originate embryonically and persist independently of monocytes.

Macrophages perform a range of essential functions. They phagocytose and destroy microorganisms, dead cells, and cellular debris, helping to clear infections and promote tissue homeostasis. They are also professional antigen-presenting cells, processing ingested material and presenting peptides on MHC class II molecules to helper T cells, thereby bridging innate and adaptive immunity. In addition, macrophages secrete a variety of cytokines and chemokines that orchestrate inflammation, recruit additional immune cells, and regulate wound healing and tissue remodeling.

Macrophages are widespread and highly specialized in different tissues. Examples include Kupffer cells in the liver, microglia in the brain, alveolar macrophages in the lungs, and osteoclasts in bone. Their activity is shaped by signals in the tissue environment; they can adopt different activation states. A simplified framework distinguishes pro-inflammatory M1 macrophages, induced by signals such as IFN-γ and LPS, from anti-inflammatory or reparative M2 macrophages, promoted by IL-4 and IL-13. In reality, macrophage polarization exists along a spectrum and integrates multiple cues.

Macrophages contribute to both health and disease. While essential for host defense and tissue maintenance, dysregulated macrophage activation or chronic polarization can drive inflammatory diseases, atherosclerosis, obesity-related inflammation, and cancer. Tumor-associated macrophages, for example, can support or suppress tumor growth depending on their environmental cues.