VLA-4-dependent adhesion activities of U937 cells and guinea pig bronchoalveolar lavage leukocytes.

VLA-4-dependent binding to fibronectin (FN) and to a human vascular cell adhesion molecule (hVCAM-1)-transfected murine cell line was measured using U937 cells and guinea pig (GP) bronchoalveolar lavage (BAL) cells. A species cross-reactive, blocking monoclonal antibody directed against human VLA-4 (TY 21.6) inhibited U937/FN binding by 71 +/- 7%. The presence of TY21.6 inhibited the stimulated binding of U937 cells to hVCAM-1 by 84%. However, TY 21.6 was unable to inhibit the BAL/FN binding. With the addition of TY 21.6, the binding of PMA-stimulated BAL cells to hVCAM-1 was inhibited by 57 +/- 5%. In summary, human and guinea-pig leukocytes express binding activity to both FN and hVCAM-1. A specific VLA-4 blocking monoclonal antibody, TY 21.6, inhibited U937 and BAL cell binding to hVCAM-1, but only inhibited FN binding with U937 cells.