results of these studies indicate that leukocyte/epithelial cell interactions are characterized by five successive stages : ( 1 ) leukocyte adhesion to superficial layer of the epithelium , ( 2 ) leukocyte penetration beneath the superficial epithelium , ( 3 ) epithelial cell injury , ( 4 ) leukocyte phagocytosis of killed epithelial cells and ( 5 ) ulceration and total destruction of the full thickness of the epithelial layer .
C0014609
epithelium
C0014597
epithelial cells