Which cells are responsible for targeting abnormal and virally infected cells?

Natural killer cells are a crucial component of the innate immune system, specifically designed to identify and eliminate cells that are abnormal or infected by viruses. These lymphocytes have the unique ability to recognize distressed cells that exhibit signs of stress, such as altered MHC (Major Histocompatibility Complex) expression or the presence of certain ligands on their surface. Upon detecting these changes, natural killer cells can induce apoptosis, or programmed cell death, in the compromised cells, thereby preventing the spread of infection and contributing to immune surveillance.

In contrast, macrophages primarily function by phagocytosing pathogens and dead cells, eosinophils are mainly involved in combating parasitic infections and mediating allergic responses, and mast cells play a critical role in the inflammatory response and allergy through the release of histamine and other mediators. Therefore, while all these cell types are important in immune function, natural killer cells are uniquely equipped to specifically target and eliminate abnormal and virally infected cells.