Homing-associated cell adhesion molecule (H-CAM/CD44) on human CD34+ hematopoietic progenitor cells.

Human CD34+ hematopoietic progenitor cells (HPCs) express CD44 and can directly adhere to hyaluronate (HA) via CD44. Furthermore, CD44 may also be involved in the regulation of CD34+ HPC proliferation and development. The expression of CD44 molecules on CD34+ hematopoietic progenitor cells is significantly lower on bone marrow (BM) CD34+ cells compared with circulating CD34+ cells in cord blood and peripheral blood. Myeloid and erythroid progenitor cells are found predominantly in CD34+ CD44+ cell fractions. More interestingly, CD34+ CD44- cells expressing B-lymphocyte-associated CD10 and CD19 would represent unique B-lymphocyte committed precursors in the BM, which might undergo apoptotic cell death in the early steps of B-cell differentiation.