تسجيل الدخول

تسجيل

Role of Macrophages in Tissue Repair

المؤلف:  Abbas, A. K., Lichtman, A. H., Pillai, S., & Henrickson, S. E.

المصدر:  Cellular and Molecular Immunology (2026)

الجزء والصفحة:  11E, P96

2026-05-11

240

Macrophages play a key role in eliminating damaged cells and initiating tissue repair after injury. Acute inflammation is often associated with significant death of host cells, which may be caused by microbes or by activated leukocytes. Once the offending agents are eliminated, the debris from dead cells has to be cleaned up and the damaged tissue has to be repaired. Macrophages play a critical role in the repair process because of several activities. Macrophages clear dead cells and secrete growth factors that promote regeneration and angiogenesis. Macrophages also secrete TGF-β and other cytokines that stimulate collagen synthesis by fibroblasts, thus promoting the formation of scar tissue to replace the damaged parts. Macrophages activated in different ways are responsible for different functions: classically activated macrophages are microbicidal and promote inflammation early in the reaction, while alternatively activated macrophages promote tissue repair.

Macrophages also perform the important function of removing apoptotic cells. In innate immune responses, infected cells may undergo apoptosis because of the action of activated NK cells or TNF. In addition, many of the neutrophils that are recruited into an inflmammatory site die by apoptosis within hours of leaving the circulation. Apoptotic cells and their fragments express surface molecules, such as phosphatidylserine, derived from the inner lipid layer of the plasma membrane. These molecules are recognized by receptors on macrophages, such as TIM-4, leading to the phagocytosis of the apoptotic cell, a process called efferocytosis. Phagocytosis of apoptotic cells is called efferocytosis. Macrophages play a similar role in clearing infected cells that have undergone apoptosis induced by CTLs in adaptive immune responses. Apoptotic cells suppress the inflammatory reactions of macrophages, thus ensuring clearance of the dead cells without the potentially damaging effects of inflammation.