Integrin-Associated Protein (IAP, Also Termed CD47) Is Involved in Stroma-Supported Erythropoiesis

Abstract

Erythropoiesis is regulated by the hematopoietic microenvironment of the spleen, fetal liver, and bone marrow in mice. We previously showed that established stromal cells from these organs selectively support erythropoiesis in vitro. To identify the cell surface molecule (s) on the stromal cells involved in erythropoiesis, we raised monoclonal antibodies (MAbs) to MSS 62 stromal cells derived from newborn spleen and obtained MAb 100.1, which partially inhibited the stroma-supported erythropoiesis in vitro. Using an expression cDNA library of MSS 62 cells, we cloned a gene encoding the protein recognized by MAb 100.1 and identified it as integrin-associated protein (IAP, also termed CD47), which may play a general role in integrin-mediated signal transduction. IAP/CD 47 is expressed in the stromal cells of spleen, fetal liver, and bone marrow, and in a variety of hematopoietic cells including erythroblasts. Thus, IAP may be partly involved in the erythropoietic supporting ability of the stromal cells.