Identification of a human B-cell/myeloid common progenitor by the absence of CXCR4.

CXCR4 is a chemokine receptor required for hematopoietic stem cell engraftment and B-cell development. This study found that a small fraction of primitive CD34(+)/CD19(+) B-cell progenitors do not express CXCR4. These CD34(+)/CD19(+)/CXCR4(-) cells were also remarkable for the relative lack of primitive myeloid or lymphoid surface markers. When placed in B-lymphocyte culture conditions these cells matured to express CXCR4 and other surface antigens characteristic of B cells. Surprisingly, when placed in a myeloid culture environment, the CXCR4(-) B-cell progenitors could differentiate into granulocyte, macrophage, and erythroid cells at a high frequency. These data define a novel B-cell/myeloid common progenitor (termed the BMP) and imply a less restrictive pathway of myeloid versus lymphoid development than previously postulated.