Culture system for extensive production of CD19⁺IgM⁺ cells by human cord blood CD34⁺ progenitors

Abstract

We established a co-culture system with a monolayer of the murine bone marrow (BM) stroma cell line, MS-5, in which human cord blood CD34⁺ cells differentiated to CD19⁺ cells. The addition of stem cell factor (SCF) and granulocyte colony- stimulating factor (G-CSF) highly enhanced the production of CD19⁺ cells. The expansion of the cell numbers was over 10³-fold. Furthermore, a significant proportion (<45%) of the cells expressed surface igm (sigm) after 5 weeks of co-culture. cd34⁺CD19⁻ cells also showed a similar development of CD19⁺ cells and CD19⁺sIgM⁺ cells. Filter separation of MS-5 cells and CD34⁺ cells did not inhibit the growth of CD19⁺ cells. However, when further purified CD34⁺CD19⁻CD13⁻ CD33⁻ cells were cultured in the presence of MS-5 cells with or without a separation filter, CD19⁺ cells did not appear in the non-contact setting. This result suggested that the highly purified CD34⁺CD19⁻CD13⁻CD33⁻ progenitors require the cell–cell contact for the development of CD19⁺ cells, whereas other CD34⁺ fractions contain progenitors that do not require the contact. This co-culture system should be useful for the study of early human B-lymphopoiesis.