Effect of PACs and aspirin on leukocyte cell adhesion molecules during carrageenin-induced pleurisy. The relative expression by circulating granulocytes of LFA-1, Mac-1 and VLA-4 were measured using flow cytometry. Granulocytes were incubated with saturating concentrations of monoclonal antibodies (mAb): R-PE-conjugated WT.1 against rat CD11a (LFA-1) (A), FITC-conjugated WT.5 against CD11b (Mac-1) (B) or FITC-conjugated MRα4-1 against CD49d (VLA-4) (C). mAb against CD11a gave negative results for all tested groups. PACs induced up-regulation of CD11b and CD49d with the highest dose tested and down-regulation of CD49d with the lowest dose. Aspirin also down-regulated CD49d at 200 mg/kg. Each value is the mean ± s.e. mean of n = 6 experiments. *P < 0.05 versus carrageenin.