Final answer:
Granzymes entering target cells trigger apoptosis, a programmed cell death pathway, through the formation of pores in the cell membrane by perforins, released by immune cells like NK cells and cytotoxic T lymphocytes.
Step-by-step explanation:
When granzymes enter target cells, they activate a cell-intrinsic programmed cell death pathway known as apoptosis. Natural Killer (NK) cells and cytotoxic T lymphocytes use a lethal hit mechanism to target and kill cells that may be infected with viruses or are tumorous. The granules of these immune cells release proteins called perforins that form pores in the plasma membrane of the target cells. Through these pores, granzymes, which are serine proteases, enter the cell and initiate apoptosis, a process of programmed cell death.
Apoptosis is characterized by a series of events including chromatin condensation, DNA fragmentation, and the formation of apoptotic bodies that are then cleared by phagocytic cells without causing inflammation, which is characteristic of necrosis. This process helps to maintain the health of the organism by eliminating cells that may pose a threat due to disease or genetic damage.
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