Fig. 2. Opioid-containing leukocytes in the inflamed paw during late inflammation: Rats were intraplantarly injected with Freund’s complete adjuvant, and 48 h later, triple-color flow cytometry was performed on cell suspensions of the inflamed paw. A gate was set on CD45+leukocytes, and these were analyzed for expression of opioid peptides (3E7+cells, y-axis ) and of the monocyte/macrophage marker ( A , ED1+cells, x-axis , percentage of total CD45+leukocytes in each quadrant). The majority of all opioid-containing leukocytes were monocytes/macrophages ( upper right vs. upper left quadrant , representative results of three independent experiments). Staining with isotype matched control antibodies is shown in B . FITC = fluorescein isocyanate; Ig = immunoglobulin; PE = phycoerythrin.