Molecular analysis of V(H)I+ B lymphocytes in hepatitis C patients

Hepatitis C: the complications of immune dysfunction

Hepatitis C virus (HCV) infection has been linked to numerous diseases of immune dysfunction, including, but not limited to, essential mixed cryoglobulinemia and non-Hodgkin's lymphoma. Clinical studies support these associations and treatment of the underlying HCV infection has been variably successful. Recent studies, focusing on the role of HCV gene products, have discovered evidence of dysregulated responses in multiple aspects of host immunity that may be contributing to the genesis of these diseases. Novel treatments that target these areas of dysregulation offer hope for improved therapy for the diseases associated with immunodysregulation by HCV.

Virological analysis and phenotypic characterization of peripheral blood lymphocytes of hepatitis C virus-infected patients with and without mixed cryoglobulinaemia

In clinical and pathological terms hepatitis C virus (HCV)-infected patients can be subdivided into two main groups with and without mixed cryoglobulinaemia (MC). Involvement of blood mononuclear cells by HCV has potentially important implications. To this end, HCV-RNA levels in peripheral blood lymphocytes (PBL) preparations of 20 chronically HCV-infected patients with MC were measured and compared with those found in a group of 20 patients without MC matched for age, serum HCV-RNA, infectious genotype, source and presumable duration of infection. Phenotypic abnormalities of PBL subsets in each group of patients were determined by cell surface marker expression and compared. Results showed a significant enrichment of HCV-RNA in PBL of MC patients compared with a non-MC group (P = 0.01). Different distribution of HCV-RNA was accompanied by evidence of an increased frequency of circulating B cells. These data indicate that MC patients are characterized distinctly by a higher quota of cell-associated viral load.

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.

Molecular methods to distinguish reactive and neoplastic lymphocyte expansions and their importance in transitional neoplastic states

Although lymphoma and leukemia usually can be diagnosed by routine cytology and histology, some cases present a diagnostic challenge for pathologists and clinicians. Often the dilemma lies in determining whether a population of lymphocytes is reactive or neoplastic. We review currently available methods for analyzing lymphocyte populations by immunophenotyping and by identifying clonally rearranged immunoglobulin and T-cell receptor genes and discuss how these tests can be used to clarify such diagnostic dilemmas. We also describe the detection of chromosomal abnormalities and methods on the horizon, such as gene expression profiling, to identify diagnostically useful oncogenes. Finally, we review the emerging concept of transitional neoplastic states, in which reactive lymphocytes transform to neoplastic lymphocytes in the presence of continued antigenic stimulation, such as that caused by infection with Helicobacter pylori. The existence of transitional neoplastic states underscores the need for an array of molecular diagnostic tools that would improve our ability to characterize lymphocyte populations in human and animal patients and enhance early detection of neoplastic lymphocytes such that eradication of the infectious or inflammatory stimulus could lead to cure.