tissuesneutrophils

Tissues neutrophils are neutrophils that reside in or migrate into body tissues as part of the immune response, rather than circulating primarily in the bloodstream. Neutrophils originate in the bone marrow, enter the circulation, and can rapidly exit vessels at sites of infection or injury in response to chemotactic signals and adhesion molecules. Once in tissue, they participate in early defense against microbes and orchestration of the inflammatory response.

In tissue, neutrophils perform several core functions. They phagocytose pathogens, release cytotoxic granule contents such as proteases and antimicrobial peptides, and generate reactive oxygen species through a respiratory burst. They can also form neutrophil extracellular traps (NETs), which trap and kill microbes in the extracellular space. Neutrophils have a relatively short tissue lifespan, typically dying by apoptosis within hours to a couple of days, and are cleared by resident macrophages as part of normal resolution of inflammation.

Clinical and pathological relevance is centered on their role as markers of acute inflammation. Presence of tissue neutrophils suggests recent infection or injury, particularly bacterial; excessive or prolonged infiltration can contribute to tissue damage and complications in conditions such as sepsis or autoimmune inflammation. In chronic lesions, neutrophils may be present alongside other immune cells, reflecting ongoing inflammatory activity. In oncology, neutrophil infiltration into tumors can influence tumor progression and response to therapy, though outcomes vary by context.

Histologically, neutrophils are identified by multilobed nuclei and granular cytoplasm, with myeloperoxidase staining often used to highlight them in tissue sections.