Longitudinal sections from E. crypticus controls (A, C) and specimens treated with 100 nM OA for 24 h (D) and 200 nM OA for 12 h (B) stained with gallocyanin-chrome alum (A), Mallory-Azan stain (B) and immunostained with anti-IL-6 polyclonal antibody (C, D). (A) The chloragogenous tissue (c) from controls formed one or two layers of round vacuolated and basophilic cells surrounding the intestine (i). (B) After OA treatment, the tissue showed a higher number of cell layers and expanded into the celomatic cavity. The toxin also induced an increase in the number of circulating celomocytes. (C, D) Immunonegative chloragocytic cells, arrows; immunopositive amoebocytes, arrowheads. Bar = 10 μm. (Reprinted with permission, modified from [68]).