Molecular characterization of B cell clonal expansions in the liver of chronically hepatitis C virus-infected patients.

PCR DNA amplification of IgH genes was performed on liver biopsy samples of 42 unselected hepatitis C virus (HCV)-positive patients. Genotypic analysis and signal amplification by branched DNA were used to characterize and quantitate HCV RNA genomic sequences. Intraportal lymphoid follicle-like structures were isolated from surrounding hepatocytes by microdissection technique. IgH VDJ PCR products were cloned and sequenced. IgH VDJ gene rearrangements were detected in the liver of 26 (62%) patients. Unequivocal monoclonal or oligoclonal patterns of B cell expansions were found in 14 (33.3%) and 12 (28.6%) patients, respectively. Patients with intrahepatic B cell monoclonal expansions showed liver HCV RNA levels higher than those with oligoclonal or polyclonal features (1106.4 +/- 593.5 vs 677.3 +/- 424.3 vs 406.2 +/- 354.3 pg HCV RNA/g tissue; p = 0.048 and p = 0.001, respectively). Although a single dominant band was obtained with total DNA, characterization of DNA recovered from intraportal inflammatory aggregates resulted in the detection of multiple IgH VDJ gene rearrangements, pointing to an oligoclonal pattern of lymphoproliferation. Cloning and sequence analyses showed that B cell clonalities were differently distributed in adjacent portal tracts of the same liver area. In addition, HCV RNA genomic sequences could be consistently amplified from each of the portal inflammatory aggregates examined. These data support the concept that in chronic HCV infection the intrahepatic B cell repertoire is frequently clonally restricted and that HCV may have a direct role in sustaining in situ B cell proliferation.

The lymphoid system in hepatitis C virus infection: autoimmunity, mixed cryoglobulinemia, and Overt B-cell malignancy.

Like other hepatotropic viruses, hepatitis C virus (HCV) shares the property of inducing hepatocellular damage, possibly through induction of immune mechanisms that lead to hepatocellular necrosis. After infection of hepatocytes, and possibly other cells, humoral and cellular responses occur aimed at prevention of virus dissemination and elimination of infected cells. The early activated mechanisms include production of nonspecific and specific antibodies that represent the first-line of defense against invading foreign pathogens. As a consequence, circulating immune complexes are promptly formed, and antigen uptake and processing by specialized cells are enhanced. A major fraction of circulating immunoglobulins (Igs) are part of the spectrum of the so-called natural antibodies, which include anti-idiotypic antibodies and molecules with rheumatoid factor (RF) activity. They mainly belong to the IgM class, are polyclonal, and have no intrinsic pathogenetic potential. In 20-30% of HCV-infected patients, RFs share characteristics of high affinity molecules, are monoclonal in nature, and result in the production of cold-precipitating immune complexes and mixed cryoglobulinemia. It has been shown that anti-idiotypic antibodies and polyclonal and monoclonal RF molecules have the same cross-reactive idiotype, called WA, suggesting that their production is highly restricted. This strongly indicates that they arise from stimulation with the same antigen, likely HCV. It has also been speculated that B-1 (CD5+) and B-2 (CD5-) B-cell subsets, which use a limited number of VH germline genes, underlie the production of low-affinity polyclonal and high-affinity monoclonal antibodies, respectively. The persistent production of monoclonal RF molecules implies the existence of a further mechanism capable of restricting the reactivity and reflects a distinct selection of a cell population that can be maintained throughout life because they are continuously exposed to antigen pressure. Either polyclonal or monoclonal profiles of B-cell expansion are demonstrable in the liver of most HCV-infected patients. The occurrence of B-cell clonal expansion is strictly related to intrahepatic production of RF molecules, and this suggests that liver is a microenvironment, other than lymphoid tissue, in which a germinal centerlike reaction is induced. The frequent detection of oligoclonal B-cell expansion may, indeed, represent a key pathobiologic feature that sustains nonmalignant B-cell lymphoproliferation. The preferential expansion of one clone would in turn lead to a monoclonal pattern that could favor stochastic oncogenic events. It can be postulated that HCV is the stimulus not only for the apparent benign lymphoproliferative process underlying a wide spectrum of clinical features, but also for the progression to frank lymphoid malignancy in a subgroup of patients. Current data indicate a higher prevalence of overt B-cell non-Hodgkin's lymphoma in HCV-infected patients, especially in some geographic areas.

Localized AL amyloidosis of the colon and clinical features of intestinal obstruction. A case report.

The term amyloidosis refers to a group of disorders characterized by the extracellular accumulation of insoluble, fibrillar proteins (i.e. amyloid) in various organs and apparatuses. Local deposition of amyloid without systemic involvement is a rather uncommon form that gives rise to an amyloid pseudo-tumor or "amyloidoma". This paper describes the clinical features of an intestinal subocclusion observed in an elderly patient with localized primary amyloidosis of the transverse colon. The endoscopic picture indicated a stenosing neoplasm. Segmentary colectomy, however, followed by histological examination (characteristic green color in polarized light after staining with Congo red) and immunohistochemical analysis of the resected tissue, revealed massive deposits of amyloid composed of lambda light chains in the interstitial connective, and perivascular tissue and muscular tunic, and resulted in a diagnosis of AL amyloidosis. This was successfully treated with a combination of melphalan and prednisone.