drápsfrumur

Drapsfrumur, often translated as "killer cells," is a term used in some contexts, particularly in popular science or less formal scientific discussions, to refer to lymphocytes that are involved in the immune system's defense against infected or cancerous cells. The most prominent type of cell referred to by this term is the natural killer (NK) cell, a crucial component of the innate immune system. NK cells are responsible for recognizing and eliminating cells that display stress signals or lack specific surface markers, such as MHC class I molecules, which are often downregulated by viruses or tumor cells to evade detection by other immune cells.

These cells do not require prior sensitization or antigen presentation, unlike T cells, to initiate their cytotoxic activity. Upon encountering a target cell, NK cells release cytotoxic granules containing perforin and granzymes. Perforin forms pores in the target cell membrane, allowing granzymes to enter and trigger apoptosis, programmed cell death. This rapid response mechanism is vital for controlling viral infections in their early stages and for surveilling the body for the development of tumors. While "drápsfrumur" is not a formal scientific classification, it effectively conveys the cytotoxic function of these important immune cells.