The inflammatory response in pediatric biliary disease: macrophage phenotype and distribution

Extrahepatic biliary obstruction in infants and children leads to ductal hyperplasia and portal fibrosis. Inflammatory mediators responsible for increased cellular proliferation and matrix deposition are hypothesized to result from the intrahepatic recruitment and activation of lymphocytes and macrophages (M phi). The authors previously showed components of this mechanism in studies that demonstrated increased adhesion molecule expression in biliary atresia, as well as evidence of altered hepatic M phi function during the course of experimental cholestatic liver injury. Therefore they sought determine the expression of macrophage receptor markers CD68 and CD14 in pediatric biliary disease.

Sixteen liver specimens were snap-frozen and cryosectioned onto polylysine-coated slides. Sections were stained with murine monoclonal antibodies to CD68 (resident M phi) and CD14 (monocyte-M phi lipopolysaccharide [LPS] receptor) glycoproteins. The sections were analyzed using a semiquantitative scale of proliferation and were position-graded from 0 to 3 (maximal).

Blinded analysis showed that marked proliferation of CD68-positive cells occurred in five of the six patients with biliary atresia (BA) and in one patient who had severe cholestasis. Normal perisinusoidal liver M phi were found in specimens from patients with hepatitis (2), choledochal cyst (1), and congenital hepatic fibrosis (1). Similarly, expression of CD14 periportal M phi was found only in patients with BA or cholestasis (1.9 +/- 0.3 [mean +/- SEM]) and was absent in other diseases. Strong sinusoidal expression of CD14 was evident in all patients who had extrahepatic biliary obstruction. An early biopsy specimen from a premature infant with BA did not show cholestasis, fibrosis, CD68 Mø proliferation, or CD14 expression; however, another biopsy specimen, obtained further in the course of jaundice showed the progressive development of all features.

These findings suggest proliferation of resident M phi in association with cholestasis. The presence of the LPS receptor on periportal cells during cholestatic liver injury points to a potential source of cytokines responsible for the inflammatory reaction of biliary atresia.