Upon induction of IL-7, the B220<sup>+</sup> c-kit<sup>+</sup> Pro/Pre-B I compartment in the bone marrow increased as compared to control mice in a serum IL-7 concentration-correlated manner.
In the absence of CHD4 in B cell progenitors in vivo, development of these cells is arrested at an early pro-B-like stage that is unresponsive to IL-7 receptor signaling and unable to efficiently complete V(D)J rearrangements at <i>Igh</i> loci.
In vitro, bone marrow cells from young mice formed unique mixed pro-B lymphoid (B220(+)CD19(+)CD43(+)sIgM(-), PAX5(+), TdT(+), IgH rearranged)/myeloid (CD11b/Mac1(+), c-fms(+), lysozyme(+)) colonies when grown in IL-7- and Flt3 ligand-containing media.
The present cell line should constitute a useful model of t(7;9) early pre-B ALL and allow investigation of the relationship between IL-4 and IL-7 negative signaling in leukemic B cell ontogeny.