Haemonectin, a bone marrow adhesion protein specific for cells of granulocyte lineage.

There is substantial evidence that the haematopoietic microenvironment is crucial to the growth and differentiation of haematopoietic cells. This microenvironment is composed of stromal cells, soluble factors and extracellular matrix (ECM). We have shown that a complex extract of bone marrow ECM can stimulate the growth and differentiation of haematopoietic cells in vitro. Furthermore, the use of inhibitors or stimulators of ECM synthesis in long-term marrow culture affects cell proliferation. On a molecular level, however, the interactions between ECM and haematopoietic cells are not well understood. We have investigated the adhesion between specific bone marrow ECM components and haematopoietic cells, and found a protein, 'haemonectin', of relative molecular mass 60,000 in bone marrow ECM which is a lineage- and organ-specific attachment molecule for cells of granulocyte lineage. This specificity distinguishes haemonectin from previously described adhesion proteins which have a wider tissue distribution and cell type specificity.