Expression of CD24 on CD19-CD79a+ early B-cell progenitors in human bone marrow

CD24 is a surface marker expressed in immature and mature B cells and involved in cellular adhesion and apoptosis. There are no data, which delineate the stage in early development of human B cells, which marks the expression of CD24. We studied lymphopoiesis in normal pediatric bone marrow (BM) and found that 1.5 +/- 0.2% of WBC were CD24(+) lymphocytes which did not express CD19. A significant fraction of these cells expressed low levels of CD45 (CD19(-)CD24(+)CD45(low) cells). Small numbers of CD19(-)CD24(+)CD45(low) cells were found in the regenerating BM of children with acute lymphoblastic leukemia after the completion of chemotherapy and in normal adult BM. Flow cytometric analyses have shown that CD19(-)CD24(+)CD45(low) lymphocytes express CD10, CD34, CD79a, CD79a (VpreB), and TdT markers, i.e., displayed antigenic properties of early B-cell progenitors. Our data indicate that CD19(-) early B-cell progenitors in human BM express CD24, and that the expression of CD24 in human B-cell development precedes the expression of CD19. (c) 2005 Elsevier Inc. All rights reserved.