Natural killer cells.
D000367:Age Factors; D000818:Animals; D003602:Cytotoxicity, Immunologic; D006412:Hematopoietic Stem Cells / Q000276:immunology / Q000502:physiology; D006801:Humans; D007694:Killer Cells, Natural / Q000276:immunology / Q000502:physiology*; D051379:Mice; D008815:Mice, Inbred Strains; D009000:Monocytes / Q000502:physiology; D013154:Spleen / Q000166:cytology