Lineage marker-negative lymphocyte precursors derived from embryonic stem cells in vitro differentiate into mature lymphocytes in vivo.

We induced differentiation of mouse embryonic stem (ES) cells into lymphoid cells by culturing in methylcellulose, followed by the co-culture with a bone marrow stromal cell line ST2 in the presence of IL-7. These lymphoid cells expressed transcripts of the recombination activating genes, RAG-1 and RAG-2, as well as the C mu gene, although the lymphoid cells did not express surface antigens specific to T or B lymphocytes such as T200, CD4, CD8 and B220, or transcripts of B lymphocyte-specific genes such as lambda 5 and mb-1. D-J rearrangement was detectable in the lymphoid cells differentiated from ES cells in vitro and a sizeable number of both B and T lymphocytes were generated in vivo when the ES-derived lymphoid cells were transferred into RAG-2-deficient mice, which contain no B or T lymphocytes. The results indicate that in the in vitro co-culture system, ES cells give rise to immature lymphocyte precursors which have potentials to differentiate into both mature B and T lymphocytes in vivo. The ES-derived lineage marker-negative lymphocyte precursors would thus provide useful materials for studying early events of lymphopoiesis.