Fig. 7.

IL-22 producing cells in the gills. Rainbow trout were infected by i. p. injection of A. salmonicida or PBS as control. Gill samples were collected for detection of IL-22 producing cells by immunohistochemistry using anti-IL-22 mAb L8. Each slide was counter-stained with hematoxylin (HE). Primary gill lamellae (PGL) and secondary gill lamellae (SGL) are shown. Black arrow heads indicate IL-22⁺ staining. Representative images from two control fish or two infected fish are shown at 40× magnification (left images, scale bars = 100 μm) and at 100× magnification (right images, scale bars = 50 μm). (A, B) Relatively few, weakly positive cells were observed in the control fish 24 h post injection. (C, D) Intense staining was seen in the epithelium of the PGL and SGL of A. salmonicida challenged fish.