LFA-1 blockade does not act directly to induce CD62L down-regulation. CD8⁺ OT-I and CD4⁺ OT-II T cells were stimulated in vitro with cognate Ag as described in “Methods,” or were left unstimulated and analyzed by flow cytometry 72 hours later. Anti–LFA-1 treatment of unstimulated CD8⁺ (A) or CD4⁺ (B) T cells did not result in down-regulation of CD62L or CD43 or change the expression of CD69. Similarly, anti–LFA-1 treatment did not affect the expression of these molecules on peptide-stimulated CD8⁺ (A) or CD4⁺ (B) T cells. Flow cytometric plots shown are gated on either CD4⁺ or CD8⁺ T cells as indicated and are representative data of 3 independent experiments. Summary graphs are cumulative results from 3 independent experiments and P > .05 comparing anti–LFA-1–treated samples with untreated controls.