Treatment of Jβ2/LFA-1 cells or T blasts with activating or blocking antibodies enhances α₅β₁ and does not reduce α₄β₁ adhesion and migration on fibronectin. Jβ2.7/LFA-1 cells (A) or T blasts (B) were treated with α₄ or α₅ blocking antibodies and the LFA-1 activating antibody CBR LFA-1/2 or neutral antibody TS2/4 or left untreated. Cells were allowed to adhere to fibronectin, unbound cells washed off, and bound cells quantified from 6 screens in triplicate. Amounts of bound cells and standard deviations are shown. (C) T blasts were treated as earlier and allowed to migrate over a fibronectin-coated filter for 1 hour. Migrated cells were quantified from 3 independent experiments. *P < .05.