Description
CD34 is a cell surface antigen formerly known as hemopoietic progenitor cell antigen-1. CD34 is expressed selectively on human hematopoietic progenitor cells. The biological function of CD34 is still unknown. It is used as a surface marker for very early hematopoietic stem cells. Cells expressing CD34 respond to SCF (stem cell factor ) and LIF in the presence of colony stimulating factors and these factors can induce myeloid differentiation in these cells. The effects of some growth factors on cells expressing CD34 are counteracted by IP-10, a factor the expression of which is induced by IFN-gamma. The proliferation of human CD34 cells is stimulated also by IL- 11, and IL11 synergises with SCF, IL-3, and GM-CSF. In the presence of human IL-17, fibroblasts can sustain the proliferation of CD34 hematopoietic progenitors and their preferential maturation into neutrophils