Natural killer (NK) cells are a type of innate immune cell that play a crucial role in the body's defense against viral infections and cancer. They are able to recognize and kill infected or abnormal cells without prior activation or the need for specific antigens. NK cells are also involved in regulating the immune response by producing cytokines that can enhance or suppress immune activity. Research in the field of NK cells aims to understand the mechanisms by which these cells recognize and target abnormal cells, as well as to explore potential therapeutic applications. This includes investigating how NK cell function can be manipulated or enhanced to improve immune responses against cancer or infectious diseases. Overall, research on NK cells is important for advancing our understanding of the immune system and developing new strategies for treating a variety of diseases.