Expression of CB2 receptors in peripheral blood mononuclear cells. (A) Mononuclear leukocytes were isolated and labeled for flow cytometric analysis as reported in Materials and Methods. Each staining profile for CB2 receptor expression (solid line) was overlayed with the negative control (dotted line) performed by preincubating anti-CB2 receptor Abs with the C-terminal synthetic peptide. The four staining profiles were obtained after positionning a region of interest on cells expressing CD3⁺ CD4⁺ (T4 cells), CD8⁺ CD3⁺ (T8 cells), CD56⁺ (NK cells), or CD20⁺ (B cells). The histograms shown are all from one donor and are representative of three different donors. (B) Mean ± SD of CB2 receptor fluorescence intensities in peripheral blood leukocyte subsets from three different donors analyzed by flow cytometry as described in (A). For each leukocyte subset, the fluorescence intensity reported on the abcissa was calculated in arbitrary units by subtracting the irrelevant control (anti-CB2 receptor Abs + specific peptide) from the anti-CB2 receptor Ab labeling.