A CRITICAL ROLE OF VLA-4 IN ERYTHROPOIESIS IN-VIVO

Hematopoiesis requires specific interactions with the microenvironment s, and VLA-4 has been implicated in these interactions based on in vit ro studies. To study the role of VLA-4 in hematopoiesis in vivo, we pe rformed in utero treatment of mice with an anti-VLA-4 monoclonal antib ody. Although all hematopoietic cells in fetal liver expressed VLA-4, the treatment specifically induced anemia. It had no effect on the dev elopment of nonerythroid lineage cells, including lymphoids and myeloi ds. In the treated liver almost no erythroblast was detected. whereas the erythroid progenitors. which give rise to erythroid colonies in vi tro, were present. These results indicate that VLA-4 plays a critical role in erythropoiesis, while it is not critical in lymphopoiesis in v ivo. (C) 1996 by The American Society of Hematology.