Adhesion molecule expression by bone marrow CD34-positive cells in aplastic anemia before and after immunosuppressive therapy

Summary Appropriate adhesion between bone marrow stem cells and the marrow microenvironment is necessary for hematopoiesis, since signals that promote maturation or apoptosis are transmitted from stromal cells to stem cells. In aplastic anemia (AA), interferon‐γ produced by stromal cells has more influence on the pathogenesis of marrow failure than interferon‐γ produced by lymphocytes. We evaluated the expression of cell adhesion molecules, such as very late antigen‐4 (CD49d), and ‐5 (CD49e) or c‐kit receptor (CD117), by CD34‐positive bone marrow cells in patients with AA who achieved hematological complete remission after immunosuppressive therapy. Before treatment, CD34‐positive cells showed markedly higher expression of CD49d and CD49e than cells from healthy controls, indicating the strong adhesion of stem cells to the bone marrow stroma. Expression of CD49d and CD49e was significantly decreased, reaching normal levels, after hematological recovery. These findings suggest that changes in adhesion molecule expression by stem cells are important in the pathology of AA.