Lymphoid tissue-inducer cells are hematopoietic cells essential for the organogenesis of several lymphoid structures during both fetal and adult life, whereas natural killer cells are key effector lymphocytes of the innate immune system. A series of recent reports has identified RORγt(+)NKp46(+) interleukin-22-producing cells in gut and tonsils that share features with both lymphoid tissue-inducer cells and natural killer cells and that may be involved in mucosal immunity and homeostasis.