- Sackstein, R; Fu, L; Allen, KL; Janssen, WE; Elfenbein, GJ
- Hematopoiesis occurs within bone marrow microenvironments wherein discrete cell-cell and cell-matrix interactions occur in a developmentally-specific fashion. These microenvironments are created by the regulated expression of adhesion proteins on the membrane of progenitor cells. A number of adhesion proteins have been identified on hematopoietic progenitors, among this group being the glycoprotein CD62L (L-selectin). L-selectin is a leukocyte membrane protein best known for mediating "rolling" adhesive interactions between leukocytes and vascular endothelium, however, there is also increasing evidence that it plays a role in hematopoietic events. Using an Lselectin-specific, functional, in vro lymphocyte adherence assay, we have identified a ligand for L-selectin on the human hematopoietic cell line KGla (Blood 84:3299,1994). Biochemical studies of this ligand reveal that it is an integral membrane gh/coprotetn which requires sialic acid for functional activity. This ligand is not CD34, and, moreover, flow cytometric analysis and SDSPAGE analysis of radiolabelled KG!a membrane proteins shows that the ligand does not express antigens recognized by MECA 79, a monoclonal antibody which identifies all endothelial L-selectin ligands (including a CD34 glycoform expressed on lymph node high endothelial venules}. To determine whether this novel L-selectin ligand te expressed among normal human bone marrow cells, we have performed adherence assays on freshly harvested bone marrow cells from healthy donors. We have observed L-selectin ligand activity among a subset of morphologically-immature bone marrow cells. Activity of this ligand is resistant to O-sialoglycoprotease digestion, but is sensitive to neuraminidase and a variety of proteases, exactly in parallel to the sensitivity of the KGla L-selectin ligand. Moreover, ligand activity does not correlate with CD34 expression, providing further evidence that this ligand is not CD34. The detection of an L-selectin ligand on a subset of normal human hematopoietic progenitor cells raises the possibility that this structure may mediate L-selectin-specific functional adhesive interactions during hematopoiesis.
- January 1, 1996
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