The aim of this study was to investigate whether hepatitis C virus (HCV) may perturb the immune system towards autoreactivity. We studied the relationship between the prevalence of anti-HCV and the presence of laboratory and/or clinical autoimmune features in 300 patients: lymphoid malignancies (167) and autoimmune disorders (connective tissue diseases 100; idiopathic thrombocytopenic purpura (ITP) 33). As a control, hepatitis B surface antigen (HBV) and anti-hepatitis B core antigen (anti-HBc) were related to the same parameters. Anti-HCV and anti-HBV were detected in 68/300 (22.6%) and 70/300 (24.6%) patients, respectively. HCV prevalence was 18% in lymphoproliferative disorders (anti-HBc 28.1%) and 26% in connective tissue disease (anti-HBc 16.3%). Among ITP cases, 12/33 (36.4%) were anti-HCV+ and 10/33 (30.3%) anti-HBc+. In 24/30 (80%) anti-HCV+ patients with lymphoproliferative disorders at least one serologic or clinical autoimmune abnormality was detected. To the contrary, only 10/45 (22.2%) anti-HBc+ patients with lymphoproliferative disorders had at least one serologic or clinical abnormality (P < 0.0001). A statistically significant correlation was observed between HCV prevalence and the number of autoimmune alterations in both lymphoproliferative and connective tissue disorders, which was not found for anti-HBc. These data suggest that HCV may skew the immune system toward the production of autoantibodies and also support the possibility that some cases of ITP may be linked to both HCV and HBV infection.

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SUMMARYWe have investigated which of the cytokines that are relevant in the in vitro growth of multiple myeloma (MM) malignant plasma cells are actually produced in vivo by MM patients. To this end, we have measured the levels of IL-1^, IL-3, IL-4, IL-6, IL-7, IL-8 and tumour necrosis factor-alpha (TNF-a) both in sera and in the supernatant of bone marrow (BM) stromal cell cultures from patients with MM and monoclonal gammopathy of undetermined significance (MGUS). The significance of our findings is three-fold. First, IL-6 and IL-8 are produced by MM BM stromal cells, while \h-\ji, TNF-a, IL-4 and IL-7 are not. Second, IL-3 is the only cytokine consistently raised in serum samples; we have also detected low levels of serum IL-6 in a minority of cases, usually in advanced stage ofthe disease. Third, MM BM stromal cells are active IL-6 and lL-8 producers, while both normal and MGUS BM stromal cells are low producers, thus suggesting that in the BM of MM a number of environmental cells, that would normally be quiescent, are instead activated and that, in MM, activated BM stromal cells play an active role in supporting the progressive expansion of the B cell clone.

The BM microenvironment in MM, in terms of adhesive features, is well organized to entrap circulating precursors with BM-seeking properties and is able to produce cytokines that offer them the optimal conditions for local growth and final differentiation. Likewise, the malignant B cell clone is equipped with adhesion molecules which enable the cell to establish close contacts with BM stromal cells. Furthermore a number of cytokines are released including IL-1 beta and M-CSF activating BM stromal cells to produce other cytokines, such as IL-6, that stimulate the proliferation of plasma cells. Finally, most cytokines produced locally, including IL-1 beta, TNF-beta, M-CSF, IL-3 and IL-6, also have OAF properties, explaining why the expansion of the B cell clone parallels the activation and numerical increase of the osteoclast population.

Peripheral blood mononuclear cells (PBMC) from 14 patients with multiple myeloma (MM), 3 patients with benign monoclonal gammopathy, 3 patients with Waldenstrom's macroglobulinaemia (WM) and 2 patients with B‐cell chronic lymphocytic leukemia (B‐CLL) were cultured in vitro in the presence of IL‐3 and IL‐6. After 3 days, actively proliferating immunoblast‐like B cells were apparent in 12/14 cases of MM, 0/3 BMG, 3/3 WM and 0/2 B‐CLL. After 6 d, B blasts had evolved into morphologically evident plasma cells expressing the specific monoclonal light and heavy chains. The data indicate that the concerted action of IL‐3 and IL‐6 synergistically promotes the proliferation and differentitation of circulating plasmacell precursors in malignant monoclonal gammopathies.