Murine natural killer cell progenitors and their requirements for development

Molecules that are essential to natural killer (NK) cell development have been identified mostly through characterizing knock-out mice that exhibit NK deficiencies. Such studies have shown that the interaction of membrane lymphotoxin (LT) on NK cells with its receptor on stromal elements is necessary for inducing a permissive microenvironment for NK development. Also, transcription factors such as Id2, interferon regulatory factors-1 (IRF-1), IRF-2, and Ets-1 are indispensable while PU.1 has a somewhat selective role. In addition, recent studies have identified T/NK progenitors (T/NKPs) in the fetal liver that precede migration to the fetal thymus as well as the earliest committed NK precursors in the bone marrow.