Integrin expression and function. In (A), expression of integrins (β1, 4, 5, and v) was analyzed by flow cytometry. Nontransfected Baf3 cells (designated as Baf3/c), wild-type H-Ras–transfected Baf3 cells (designated as wild-type), constitutively active type H-Ras–transfected Baf3 cells (designated as constitutively active), and dominant-negative type H-Ras–transfected Baf3 cells (designated as dominant-negative) expressed integrin β1, 4, and 5, whereas there was no expression of v integrin on the cells. There were no remarkable differences in any of these integrins between nontransfected Baf3 cells and any type of H-Ras–transfected Baf3 cells. In (B), inhibition of constitutively active type H-Ras–transfected Baf3 cells adhesion to FN without IL-3 stimulation and constitutively active type H-Ras–transfected Baf3 cells, wild-type H-Ras–transfected Baf3 cells, and dominant-negative type H-Ras–transfected Baf3 cells adhesion to FN induced by IL-3 by blocking Abs against integrin-4, 5, and β1 was examined. Data represent the means (±SD) of triplicate samples from a representative experiment of three. None of the Abs had an effect on viability of the cells. *P value (P < .01) comparing adhesion blocked by each anti-integrin antibody with that of a control antibody.