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How do granulocytes and monocytes remove bacteria and damaged cells?
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blood
Blood sediment in test tubes, showing plasma (clear fluid), red blood cells (red), and the release of hemoglobin into the surrounding plasma (pink).
Granulocytes and monocytes remove bacteria and damaged cells through a process called phagocytosis, in which the cells engulf foreign particles or debris.12
The Process of Phagocytosis
- Attraction: Both cell types are motile and are drawn to sites of infection or inflammation by chemical signals released by damaged tissues or invading microorganisms.13
- Adherence: The phagocyte must adhere to the target. If direct attachment is not possible, proteins known as opsonins—such as antibodies or complement—coat the bacteria to facilitate binding.1
- Engulfment: The cell extends its cytoplasm into pseudopods to surround the particle, eventually enclosing it within a membrane-bound vacuole called a phagosome.12
- Digestion: The phagocyte secretes hydrolytic enzymes from lysosomes into the vacuole to break down the ingested material.12
Functional Differences
- Granulocytes (specifically neutrophils): These are small, fast-acting cells that arrive quickly at the site of injury to ingest and destroy bacteria using digestive enzymes and bacteriocidal proteins.234
- Monocytes: These circulate in the blood before entering tissues to develop into macrophages. They typically arrive later than granulocytes and are primarily involved in clearing debris and chronic infections, as well as processing antigens to initiate specific immune responses.5624