Clonal B cell populations in the blood and liver of patients with chronic hepatitis C virus infection

OBJECTIVE: The association of hepatitis C virus (HCV) infection with type II mixed cryoglobulinemia is well established, but the role of HCV in B cell lymphoma remains controversial. The objective of this study was to determine the frequency of circulating and liver-infiltrating monoclonal B cells in patients with HCV infection. METHODS: One hundred sixty patients were studied prospectively, including 115 HCV-positive patients and 45 HCV-negative patients with other nonimmune chronic liver disease(s). B cell clonality was determined by DNA amplification of the IgH rearrangements, followed by polyacrylamide gel electrophoresis. RESULTS: A clonal B cell population was detected in the blood of 21 (26%) of 81 HCV-positive patients whose cryoglobulin status was known, including 12 of 25 patients with type II cryoglobulinemia, 2 of 12 patients with type III cryoglobulinemia, and 7 of 44 patients without cryoglobulins. A clonal IgH rearrangement was detected in 26 (32%) of 81 liver biopsy specimens from HCV- infected patients, including 16 patients with a circulating clonal population. A clonal B cell population was not observed in the blood of 40 patients with non-HCV liver diseases and was present in only 1 (3%) of 30 liver biopsy specimens. Logistic regression analysis showed that HCV-infected patients with clonal B cell proliferation in both the blood and liver were older (P = 0.004) and had longer duration of HCV infection (P = 0.009), higher serum cryoglobulin levels (P = 0.001) that were more frequently symptomatic (P < 0.03), and liver disease that was more severe than that in patients without a clonal B cell population in the blood or liver (P = 0.05). In 4 of 16 patients with a clonal B cell population in both the blood and liver, a definite B cell malignancy was finally diagnosed. CONCLUSION: Clonal B lymphocytes are frequently detected in the blood and liver of patients with chronic HCV infection, in the absence of overt B cell malignancy. These clones are usually, but not always, associated with the presence of type II cryoglobulins. A high percentage of patients with B cell clonality in both the blood and liver were finally diagnosed as having a definite B cell malignancy.