JAM-C mediates adhesion of untreated or phorbol myristate acetate (PMA)–stimulated U937 cells to RA and OA ST fibroblasts. The percentage of maximal adhesion was defined as the number of adherent cells on the ST sections divided by the number of adherent cells on the control sections. A, Inhibition of U937 cell adhesion to RA ST fibroblasts by both of the neutralizing antibodies against JAM-C, F26 (79% of maximal adhesion) and H33 (86% of maximal adhesion), and by an anti–Mac-1 antibody (79% of maximal adhesion). B, Additive inhibitory effect on U937 cell adhesion to RA ST fibroblasts of F26 combined with anti–Mac-1 (66% of maximal adhesion). C, Inhibition of PMA-stimulated U937 cell adhesion to RA ST fibroblasts at 37°C by F26 (71% of maximal adhesion). D, Inhibition of PMA-stimulated U937 cell adhesion to OA ST fibroblasts at 37°C by F26 (77% of maximal adhesion). Bars show the mean and SEM. See Figure 1 for other definitions.