Purification and Functional Analysis of Adfesion Related Molecules Between Hematopoietic Stem Cells and Marrow Stromal Cells.

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In order to investigate novel adhesion molecule (s) in stromal hematopoiesis, we raised monoclonal antibodies (MAb) against human marrow stromal cell lines KM-101 and KM-102 and myeloid hematopoietic cell line (CMK). The antibodies were screened by the direct addition into coculture plates containing KM cell line and K562. One of the antibodies enhanced the attachment between K562 and stromal cell lines. This antibody recognized the 135-Kilodalton membrane molecules and its Fab fragment markedly inhibited the adhesion between stromal cells and K562 cells. Immunohistochemical staining of this Mab revealed positive reaction in stromal cells of wide variety of tissues and vascular endothelia, smooth muscle cells, and some of epithelial cells including renal collecting tubules, colon and pancreatic duct. No positive reaction was found in neural cells or skeletal muscles. The distribution of the molecules are similar to CD44 antigen with a few exception, but the size of the molecules are much different. Direct binding of ^<125>I on the surface membrane of various kind of blood cells showed that peripheral white blood cells had low radiolabelling while relatively immature hematopoieticcell lines incorporated twice or more radioactive antibodies. The amount of the direct binding was modulated when the hematopoietic cell lines were treated with 10ng/ml TPA 3 days in advance. These results indicates that some sosts of exogenous stimuli modulate the expression of 135 K dalton membrane molecule. Taking together with the distribution of the molecules among a wide varieties of stroma and parenchyma, the molecules recognized by Mab C-F-9 may be one of signaling molecules between parenchymal and stromal signal transduction, as well as an adhesion related protein.