Figure 5.

Schematic representation of Id2 function in the lineage restriction of NK cells. Bipotent T/NK precursors first colonize the fetal thymus. At the stage of CD44⁺CD25⁻, some FT cells start to express Id2, which inactivates bHLH factors, probably E proteins such as HEB and E2A gene products. These cells are committed to the NK cell lineage and express CD122/IL-2Rβ. At present, the order of CD122 expression and NK cell commitment is uncertain, although our data suggest that commitment precedes CD122 expression.