A lymphocyte that can spontaneously kill a variety of target cells without prior antigenic activation via germline encoded activation receptors and also regulate immune responses via cytokine release and direct contact with other cells. [ GOC:add https://www.worldcat.org/search?q=bn%3A0781735149 http://www.ncbi.nlm.nih.gov/pubmed/15771571 ]

Synonyms: NK cell