The immune cells that cause apoptosis, a form of programmed cell death, are primarily natural killer (NK) lymphocytes.
How NK Cells Induce Apoptosis
NK cells are a type of innate immune cell that play a critical role in the body's defense against infections and cancer. They induce apoptosis, which is crucial for eliminating infected or abnormal cells.
- Mechanism: NK cells use specific serine proteases called granzymes to trigger apoptosis in target cells. Granzymes enter the target cell and activate caspases, which are enzymes that dismantle the cell from within. This leads to controlled cell death without causing inflammation.
- Targeting: NK cells recognize cells that have been altered due to infection or cancerous transformation. This ability to identify abnormal cells allows them to selectively initiate apoptosis only in the cells that need to be removed.
Other Immune Cells Involved in Apoptosis
While NK cells are specifically noted in the reference for directly causing apoptosis using granzymes, it is worth noting that other immune cells can also induce apoptosis through different mechanisms.
- Cytotoxic T lymphocytes (CTLs): Similar to NK cells, CTLs can also induce apoptosis in target cells using granzymes.
- T helper cells: Although not direct killers, T helper cells can activate other cells, like CTLs, which then induce apoptosis.
Apoptosis and Immunity
Apoptosis is critical for:
- Eliminating infected cells: Preventing the spread of pathogens by removing host cells harboring them.
- Removing cancer cells: Destroying tumor cells, thus controlling the growth of tumors.
- Maintaining homeostasis: Removing old or damaged cells, contributing to the normal functioning of tissues and organs.
In summary, the reference specifically identifies natural killer (NK) lymphocytes as effector cells that use granzymes to cause apoptosis in microbe-infected cells. While other immune cells also utilize apoptotic mechanisms, NK cells play a key role in the innate immune response through this process.
