Functional characterization of B lymphocytes generated in vitro from embryonic stem cells

To study molecular events involved in B lymphocyte development and V(D)J re arrangement, we have established an efficient system for the differentiatio n of embryonic stem (ES) cells into mature Ig-secreting B lymphocytes. Here , we show that B lineage cells generated in vitro from ES cells are functio nally analogous to normal fetal liver-derived or bone marrow-derived B line age cells at three important developmental stages: first, they respond to F lt-3 ligand during an early lymphopoietic progenitor stage; second, they be come targets for Abelson murine leukemia virus (A-MuLV) infection at a pre- B cell stage; third, they secrete Ig upon stimulation with lipopolysacchari de at a mature mitogen-responsive stage. Moreover, the ES cell-derived A-Mu LV-transformed pre-B (EAB) cells are phenotypically and functionally indist inguishable from standard A-MuLV-transformed pre-B cells derived from infec tion of mouse fetal liver or bone marrow. Notably, EAB cells possess functi onal V(D)J recombinase activity. In particular, the generation of A-MuLV tr ansformants from ES cells will provide an advantageous system to investigat e genetic modifications that will help to elucidate molecular mechanisms in V(D)J recombination and in A-MuLV-mediated transformation.