Effect of IL17A Ab on E. tenella schizont migration. Cecal tissue sections from infected chickens were taken at 5 days (A-F) and 6 days (G,H) pi. Schizonts are observed as round and red structures expressing fibronectin in chickens untreated (A,C,D,G) or IL17A Ab-treated (B,E,F,H). The muscularis mucosa (MM) is visualized as a thin and brown caveolin positive line beneath the base of the crypts. A. Migration of schizonts from the crypt epithelium to the submucosa (SM) through MM disruptions (arrowheads). Note the lamina propria (LP) diffusely infiltrated by numerous immune system cells which extend into the SM. B. Schizont groups which do not reach the SM. Note the cell infiltrates confined to the LP and the continuity of the MM. C. Schizonts, which locate deep in the LP, extend beyond the MM. Lumen of crypt fundi (*). D. Electron micrograph showing the lower portion of the LP where immature schizonts are recognizable. E. Schizonts observed in the upper portion of the LP. Lumen of crypt fundi (*). F. Electron micrograph showing schizonts recognizable as mature (thick arrow) and immature stages (thin arrow). Lumen of a crypt (*) G. Prominent cell infiltrates in the LP and SM. Arrowheads: MM disruptions. H. Light cell infiltrates located in the LP surrounding the crypts. Note inconspicuous infiltrates in the SM and the continuous MM. Bars indicate: 300 μm in A and B; 130 μm in C; 50 μm in D; 90 μm in E; 10 μm in F; 230 μm in G; 270 μm in H.