Abstract
The pathogenesis of primary biliary cirrhosis (PBC) remains enigmatic. In order to address this issue, we analyzed by laser capture microdissection and real-time reverse transcription-polymerase chain reaction the site-specific expression of messenger RNA (mRNA) for cytokines (interferon (IFN)-α, -β, -γ, interleukin (IL)-1β, -4, -6, -10, -12p40, -18, tumor necrosis factor-α) and toll-like receptors (TLRs) (TLR-2, -3, -4, -7, -9) in portal tract and liver parenchyma from patients with early-stage PBC. Expression of IFN-α, -β and TLR-3 proteins was also studied by immunohistochemistry. Autoimmune hepatitis (AIH) and chronic hepatitis C (CHC) served as disease controls. The expression levels of type I IFN (IFN-α, -β) and TLR-3 mRNAs, which are known to induce type I IFN, were significantly higher in portal tract and liver parenchyma as compared to AIH and CHC. A strong positive correlation between the mRNA levels of type I IFN and TLR-3 was also seen in both areas. Immunohistologically, IFN-α is present in the mononuclear cells in portal tract and sinusoidal cells. Macrophages in portal tract and hepatocytes expressed IFN-β and TLR-3. Furthermore, the level of IFN-α mRNA in the portal tract was positively correlated with serum alkaline phosphatase. In conclusion, these data indicate that TLR-3 and type I IFN signaling pathways are active in both the portal tract and liver parenchyma of early-stage PBC, and form the basis for our hypothesis that these signaling pathways are involved in the pathophysiology of PBC.
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