Ligation of LFA-1 on U937 cells decreased cellular binding to VCAM-1. Adhesion assay experiments for U937 cells binding to VCAM-1-FC and FC recombinant proteins were performed in the absence or presence of different concentrations of TS1-18 (A), TS1-22 (B), or immobilized ICAM-1-FC (C). The experiments were performed with 8 replicates and were repeated 3 times with similar results. Data are expressed as mean ± SD and analyzed with 2-tailed Student t test. Results showing significant differences in cellular binding in the presence of LFA-1 ligation treatments in comparison with their respective controls (isotype-matched mAb for panels A and B and immobilized FC for panel C) are marked with ^** for P < .005 or ^* for P < .05. ICAM indicates the ICAM-1-FC recombinant protein in the figures.