INCREASED CD1D EXPRESSION ON SMALL BILE-DUCT EPITHELIUM AND EPITHELIOID GRANULOMA IN LIVERS IN PRIMARY BILIARY-CIRRHOSIS

Cluster of differentiation 1 (CD1) is a family of four distinct nonpol ymorphic major histocompatibility complex class I-like molecules that can present microbial nonpeptide lipid antigens to T cells. Among the CD1 gene family, CD1d is found in a wide range of tissues including th e intestine and liver, and has been proposed to play an important role in mucosal immunity, Primary biliary cirrhosis (PBC) is an immune-med iated liver disease involving the intrahepatic small bile ducts, which also belong to the mucosal immune system. In this study, we studied t he expression of CD1d in patients with PBC and compared the data with those of patients with hepatic sarcoidosis, primary sclerosing cholang itis (PSC), chronic viral hepatitis (CVH), and normal liver as control s. CD1d was found to be expressed in hepatocytes in all cases examined , and in epithelioid granuloma cells in 19 of 22 PBC livers and in 4 o f 4 livers with hepatic sarcoidosis. In addition, CD1d was focally exp ressed on epithelial cells of the small bile ducts in approximately 50 % of the PBC patients but in no controls. Such bile duct epithelial st aining of CDld was seen in early-stage PBC and virtually absent in lat e-stage PBC, Moreover, there was no evidence of expression of CDld in large bile duct epithelial cells of PBC, The CDld on biliary epithelia l cells in PBC may be involved in the antigen presentation of microbia l lipid antigen(s) to surrounding T cells. Alternatively, modified end ogeneous lipidic compounds may share analogy with bacterial lipid anti gens and explain CDld expression, a possible epiphenomenon rather than a proof of bacterial involvement.