Phagocytosis

Phagocytosis is the cellular uptake of large particles by enclosing them in membrane-bound compartments. It enables cells to ingest microbes, debris, and other material.

Phagocytic cup: A temporary, actin-rich membrane extension that surrounds a particle during phagocytosis. The cup forms as the cell membrane extends around the target.
Phagocyte: A cell that ingests particles through phagocytosis. Phagocytosis is a defining activity of this cell class.
Innate immunity: The rapid, broadly acting defense system that recognizes common features of pathogens and tissue damage. Phagocytosis is a frontline mechanism of innate defense.
Intracellular pathogen: A pathogen that survives or replicates within host cells. Some pathogens evade destruction after being taken up by phagocytes.
Endocytosis: The uptake of extracellular material through invagination of the cell membrane into vesicles. Phagocytosis is a specialized form of endocytosis for large particles.
Actin: A cytoskeletal protein that polymerizes into filaments and helps shape and move cells. Actin remodeling drives the membrane extensions that enclose particles.
Pattern recognition receptor: A receptor that detects molecular patterns associated with microbes or tissue damage. These receptors help phagocytes detect targets that lack antibody coatings.
Antigen presentation: The display of peptide fragments on cell-surface molecules for recognition by T cells. Some phagocytes process ingested material into antigens for T-cell recognition.
Mycobacterium tuberculosis: A bacterium that causes tuberculosis and can persist within macrophages. Its survival in phagocytes illustrates how engulfment can fail to clear infection.
Pinocytosis: The uptake of extracellular fluid and dissolved substances into small vesicles. It internalizes fluid rather than engulfing large particles.

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