Answer:
NK cell
Explanation:
Natural Killer (NK) cells are a type of cytotoxic lymphocytes (i.e., white blood cells), and they are key in innate immune response. These cells are a special class of innate lymphoid cells (ILCs) which is able to protect against unknown pathogenic threats. ILCs originate from common lymphoid progenitors (like T and B cells). It has been shown that NK cells provide a quick immune response to new pathogens. In response to infection, NK cells release cytotoxic factors to lyse these infected cells.