New insights in the development of human B lymphocytes

B cells derive from pluripotent hematopoietic stem cells (HSCs), which sequentially differentiate into mature B cells through various intermediate cell types that are defined by expression of cell surface antigens. In vivo experiments to study B cell development in humans are difficult to perform. Hence, most of our knowledge about B cell development stems from studies in mice. Genetically modified mice have been instrumental not only in revealing developmental pathways, but also in elucidating mechanisms behind developmental cellular transitions. Conversely, most information on human hematopoietic development is derived from in vitro studies, and certain genetic abnormalities have greatly contributed to our understanding of some underlying mechanisms of human B cell development. Broadly, studies on human hematopoiesis seem to be consistent with principles outlined in experimental models, but the cell surface phenotypes of human transitional cell populations are often different in humans from those in the mouse. In this chapter we review, our current knowledge regarding human B cell development, including the role of cytokines, transcription factors, and microRNAs. As there have been excellent reviews on mouse B cell development, this will not exhaustively being reviewed here [1-5] although comparison of human and mouse B cell development will be outlined.