Tissue-resident natural killer cells and their potential diversity

• Mouse splenic conventional natural killer (cNK) cells have been primarily studied.
• The thymus contains NK cells that can be distinguished from cNK cells.
• The liver has cNK cells and tissue-resident (trNK) NK cells.
• Other organs may also have trNK cells, adding their potential diversity.
• We review the features of these NK cells.

Conventional NK cells are well characterized in the mouse spleen and circulate in the blood. Less well described are NK cells found in organs such as the liver, thymus, and uterus. Recently we identified a tissue-resident NK (trNK) cell population in the liver, suggesting a potential diversity of trNK cells in other organs. In this review we compare and contrast the similarities and differences among the subpopulations of NK and innate lymphoid cells to the trNK cells in the liver.