CD 44 Mediates Hyaluronan Binding by Human Myeloid K G l A and KG 1 Cells

Hyaluronan-binding function of the CD44 molecule has not been so far detected in myeloid cells. To study pure populations of primitive myeloid cells, we investigated the hyaluronan-binding function of the CD44 molecule from three myeloid cell lines: KGla, KGI, and HL60. Both KGla and KG1 cells express the CD34 antigen characteristic of the hematopoietic stem cells and HL60 cells do not; accordingly, KGla and KG1 cells are generally considered as the most primitive and HL60 cells as the most mature of these cell lines. Measurement of cell adhesion to hyaluronancoated surfaces (using 6‘Cr-labeled cells) and of aggregate formation in hyaluronan-containing solutions, showed that 45% of KG1 cells and 22% to 24% of KG1 a spontaneously bind to hyaluronan, whereas HL60 cells do not either spontaneously or after treatment with a phorbol ester. Hyaluronan binding by KGla and KG1 cells is mediated by CD44, because it is specifically abolished by monoclonal antibod-