TUNEL‐positive cells, indicating lymphocyte apoptosis, were significantly increased in number (p = 0.009) in the lamina propria of dogs fed WD in comparison to their expression in the lamina propria of dogs fed CD (TUNEL‐positive cells: CD1, 0.36% ± 0.2%; WD, 0.79% ± 0.5%; CD2, 0.42% ± 0.3%; 95% CI). Here, CD2 is linked to Wilson disease.