Evidence for a role of the integrin VLA-4 in lympho-hemopoiesis

Adhesion molecules are probably required for retention of maturing lymphocyte precursors in bone marrow, where they closely interact with and are dependent on stromal cells. Lymphomyeloid cell lines avidly adhere to cloned stromal cell lines in culture and screening pairs of these resulted in a selection strategy for a new monoclonal antibody to a leukocyte adhesion molecule. Immunoprecipitation analyses and comparison to a previously described antibody showed that it recognizes the alpha 4 chain of the integrin, VLA-4. This antibody totally inhibited lymphopoiesis and retarded myelopoiesis in long-term bone marrow cultures. A similar selection strategy resulted in two additional antibodies which define a single 100-kD species on stromal cells. This stromal cell adhesion molecule is a potential counter-receptor/ligand for VLA-4 on murine lympho-myeloid cells. Our findings suggest a new role for VLA-4 in lymphoid progenitor-microenvironment interactions. Recognition molecules that function in cell migration and inflammation in peripheral tissues may be important for steady-state lymphopoiesis within bone marrow.