Macrophagjai

Macrophagjai, or macrophages, are versatile white blood cells of the innate immune system that reside in most tissues. They originate from circulating monocytes that migrate into tissues and differentiate in response to local signals. Tissue-resident macrophagjai include alveolar macrophagjai in the lungs, Kupffer cells in the liver, and microglia in the brain, each adapted to the specific microenvironment and duties of its tissue.

Macrophagjai perform surveillance and defense by engulfing and digesting pathogens, dead cells, and debris (phagocytosis). They kill ingested microbes through reactive oxygen and nitrogen species and terminate pathogens within phagolysosomes. They also process and present antigens to T cells via MHC class II and secrete cytokines and chemokines that shape inflammation and recruit other immune cells. Macrophagjai are also involved in tissue remodeling, wound healing, and clearance of apoptotic cells.

The functional state of macrophagjai is flexible. In response to signals such as IFN-γ and microbial products they can adopt a proinflammatory M1-like profile; in contrast, signals like IL-4 or IL-13 promote an anti-inflammatory, reparative M2-like profile. In vivo, macrophagjai exist on a spectrum between these states, with plasticity allowing context-dependent responses.

Dysregulation of macrophagjai contributes to disease. They participate in chronic inflammatory conditions, atherosclerosis, and tumor progression via tumor-associated macrophagjai. Therapies under investigation target macrophagjai recruitment, survival, or polarization (for example, CSF-1R inhibitors) to modulate immune responses in infections, cancer, and autoimmune diseases.