EXPRESSION OF INTEGRINS IN HUMAN BONE-MARROW

Expression of integrins, a superfamily of glycoprotein α/β heterodimers which integrate the cytoskeleton with the extracellular matrix and/or mediate cell‐cell adhesive interactions, was examined on normal and leukaemic bone marrow cells by immunohistochemistry and immunotransmission electron microscopy (immuno‐TEM). Among the β1/VLA molecules studied, VLA‐2 and 6 were expressed on megakaryocytes and platelets, while VLA‐4 was present on 40% of haemopoietic cells, including monocytes, erythroblasts and immature cells; this molecule was typically localized at sites of intercellular contact, as seen by immuno‐TEM, suggesting it may be involved in interactions among haemopoietic cells during differentiation. In human longterm bone marrow cultures (LTBMC), VLA‐1 and 3 were present respectively on 35% and 40% of the adherent cells which included flbroblasts and endothelial cells, as shown by double‐labelling experiments; VLA‐2 was expressed only on a subpopulation of flbroblasts. β2/LeuCAM molecules were absent from platelets, megakaryocytes and HLA‐DR+/myelo‐peroxidase− early myeloid precursors, and appeared progressively during maturation in both lymphoid and myeloid cells. Expression of β3/cytoadhesin molecules was restricted to megakaryocytes and platelets and, in the adherent layer of LTBMC, to endothelial cells. The regulated expression and specific localization of integrins in the bone marrow suggest that these molecules may have a role in normal haemopoiesis. Copyright © 1990, Wiley Blackwell. All rights reserved