Neutrophils in biliary atresia. A study on their morphologic distribution and expression of CAP37

Biliary atresia is a rare pediatric disorder that results in obstructive jaundice in early infancy. Liver biopsies are characterized histologically by cholestasis, portal inflammatory infiltrate, and marked bile ductular proliferation. We studied the distribution of neutrophils in biliary atresia in patients who have undergone the Kasai procedure. Thirteen different liver biopsies were accompanied by hilar section in eight cases. Control liver specimens were from two patients with choledochal cysts, three patients with neonatal hepatitis, and three patients with alpha-1 antitrypsin deficiency. We also studied the expression of CAP37, an antimicrobial protein present in neutrophils, using immunohistochemistry in biopsy and hilar sections. Neutrophils were present in the portal tracts in all cases and widely distributed in the parenchyma in nine cases. In six cases, infiltration of neutrophils was associated with discrete foci of liver cell necrosis. There was a significantly higher number of portal tract neutrophils in biliary atresia and choledochal cyst cases than in neonatal hepatitis and alpha-1 antitrypsin deficiency (p<0.05). All neutrophils stained diffusely and strongly with CAP37. Medium staining was also seen in the proliferating portal bile ductules in six cases. This study confirms the wide distribution of neutrophils in biliary atresia, occurring as a result of bile duct obstruction. Infiltrating neutrophils are better highlighted with CAP37 immunostain. Proliferating bile ductules may play a role in the inflammatory response in biliary atresia through expression of CAP37.