Figure 3 Mu opioid receptor (MOR) immunoreactive cells in peripheral blood mononuclear cells (PBMC) and mucosal CD4⁺ and CD8⁺ T cells of patients with inflammatory bowel disease. (A, B) MOR immunostaining in PBMC of one representative Crohn's disease (CD) patient and the corresponding negative control (magnification ×100). The control, consisting of normal rabbit immunoglobulins, was negative. Insert: low magnification ×20 of MOR immunostaining of a CD patient and control. (C–F) Double immunostaining for MOR (red) and CD4 (blue) (C, D) or MOR (red) and CD8 (blue) (E, F) (original magnification ×400) in biopsies taken from one patient with CD in non‐inflamed (C, E) and inflamed (D, F) areas. Whereas only a few CD4⁺ and CD8⁺ cells stained positively with the antibody directed against MOR in the non‐inflamed mucosa, an increased number of CD4⁺ T cells (blue), MOR⁺ (red), and CD4⁺/MOR⁺ cells were observed in the inflamed mucosa of the CD patient. Scale bar represents 5 μm.