Prevalence of non-organ specific autoantibodies in HCV-infected subjects in the general population.

The significance of non-organ specific antibodies (NOSAs) in HCV-related chronic hepatitis is largely unclear. In this study we evaluated the prevalence of NOSAs in a non-selected population of HCV-infected subjects. One hundred and seventy anti-HCV positive and 192 anti-HCV negative sex and age-matched subjects (median age 64 years, range 7-91 years, female 68%) enrolled from the general population of a small Italian town were evaluated for NOSAs by indirect immunofluorescence on rat tissue sections and HEp-2 cells, and by counterimmunoelectrophoresis with thymus and spleen extracts as the antigen source. One hundred and sixty-three (96%) HCV-infected subjects had normal ALT serum levels and no evidence of liver disease. NOSAs were found in 31 out of 170 (18%) anti-HCV positive subjects and in 20 out of 192 (10%) controls (P = NS), with similar median titre (1:40) and range (1:40 to 1:160). Neither liver/kidney microsomal antibody type 1 nor antiactin reactivity were detected. No significant association between NOSAs and HCV genotypes was observed. In the general population, HCV-infected subjects and healthy controls have a similar prevalence of NOSAs. Without continuous liver damage HCV infection is unlikely to induce the appearance of NOSAs.

A 385 insertion in the hypervariable region 1 of hepatitis C virus E2 envelope protein is found in some patients with mixed cryoglobulinemia type 2.

Chronic hepatitis C virus (HCV) infection has been associated with development of mixed cryoglobulinemia type 2 (MC2), a lymphoproliferative disorder characterized by B cell monoclonal expansion and immunoglobulin M/k cryoprecipitable immunoglobulin production. A short sequence (codons 384-410) of the HCV E2 protein, which has the potential to promote B cell proliferation, was investigated in 21 patients with HCV-related MC2 and in a control group of 20 HCV carriers without MC2. In 6 of the 21 (29%) patients with MC2, all the clones isolated from plasma, peripheral blood mononuclear cells, and liver showed sequence length variation compared with the hypervariable region 1 (HVR1) consensus sequence; 5 patients had an insertion at codon 385, and 1 patient had a deletion at codon 384. Inserted residues at position 385 were different within and between patients. No such mutations were observed in any of the HVR1 clones from control patients without MC2, and the difference between the 2 groups was statistically significant (P =.02). Analysis of 1345 HVR1 sequences obtained from GenBank strongly supported the conclusion that the observed insertions and deletion represent a rare event in HCV-infected patients, suggesting that they are significantly associated with MC2. The physical and chemical profiles of the 385 inserted residues detected in the MC2 patients were consistent with the possibility that these mutations, which occurred in a region containing immunodominant epitopes for neutralizing antibodies and binding sites for B lymphocytes, may be selected by functional constraints for interaction with host cells.

Leptin regulates proinflammatory immune responses.

Obesity is associated with an increased incidence of infection, diabetes, and cardiovascular disease, which together account for most obesity-related morbidity and mortality. Decreased expression of leptin or of functional leptin receptors results in hyperphagia, decreased energy expenditure, and obesity. It is unclear, however, whether defective leptin-dependent signal transduction directly promotes any of the conditions that frequently complicate obesity. Abnormalities in tumor necrosis factor alpha expression have been noted in each of the above comorbid conditions, so leptin deficiency could promote these complications if leptin had immunoregulatory activity. Studies of rodents with genetic abnormalities in leptin or leptin receptors revealed obesity-related deficits in macrophage phagocytosis and the expression of proinflammatory cytokines both in vivo and in vitro. Exogenous leptin up-regulated both phagocytosis and the production of proinflammatory cytokines. These results identify an important and novel function for leptin: up-regulation of inflammatory immune responses, which may provide a common pathogenetic mechanism that contributes to several of the major complications of obesity.

Bile ducts and portal and central veins are major producers of tumor necrosis factor alpha in regenerating rat liver.

BACKGROUND & AIMS: Tumor necrosis factor (TNF) alpha mediates both liver injury and regeneration. Kupffer cells are thought to produce TNF because gadolinium chloride (GdCl), a drug that depletes Kupffer cells, prevents TNF-mediated injury. However, GdCl increases liver TNF and regeneration after partial hepatectomy (PH), suggesting that other cells produce TNF during regeneration. The aim of this study was to identify the source(s) of TNF after PH in normal and Kupffer cell-depleted rats. METHODS: Livers were harvested at 0, 1, or 48 hours after PH from saline- or GdCl-treated rats. TNF expression was evaluated by in situ reverse-transcription polymerase chain reaction and immunohistochemistry. RESULTS: In saline-treated rats, neither TNF transcripts nor protein was detected before PH, but both increased after PH. One hour after PH, 64% +/- 8% portal areas had TNF-positive bile ducts or veins and 61% +/- 1% central veins were TNF positive; by 48 hours, 57% +/- 1% portal areas, 40% +/- 1% central veins, and a few sinsusoidal cells expressed TNF. In GdCl-treated rats, TNF was expressed in 22% +/- 6% portal areas before PH; in 76% +/- 3% portal areas and 75% central veins at 1 hour; and in 88% +/- 2% portal areas and 80% +/- 9% central veins at 48 hours after PH. CONCLUSIONS: In the regenerating livers of both normal and Kupffer cell-depleted rats, bile ducts and veins are the predominant sources of TNF-alpha.

Kupffer cell depletion abolishes induction of interleukin-10 and permits sustained overexpression of tumor necrosis factor alpha messenger RNA in the regenerating rat liver.

Tumor necrosis factor alpha (TNF), initiates a cytokine cascade that promotes hepatocyte proliferation after 70% partial hepatectomy (PH) but the mechanisms regulating TNF production after PH are unknown. We previously reported that gadolinium chloride (GdCl), an agent that depletes the liver of phagocytically active Kupffer cells, enhances hepatic expression of TNF messenger RNA (mRNA) and promotes liver regeneration after subsequent PH. This suggests that GdCl interferes with Kupffer cell mechanisms that normally constrain TNF production after PH. To evaluate this, the pre- and post-PH expression of TNF, TNF-inducible cytokines (interleukin [IL]-1, IL-6) and cytokines (transforming growth factor [TGF] beta 1 and IL-10) that down-regulate TNF were compared in controls and GdCl-treated rats. In controls, TNF, IL-1, IL-6, and IL-10 increase within 3 hours after PH, whereas TGF-beta 1 is induced much later (> 24 hours after PH). GdCl causes sustained overexpression of TNF mRNA and transient overexpression of circulating TNF protein after PH; both TNF-inducible cytokines are also relatively overexpressed. Cytokines that down-regulate TNF are effected differentially by GdCl. Regenerative induction of IL-10 is abolished but TGF-beta 1 induction is unaltered. Because IL-10 is known to shorten the half-life of TNF mRNA, these results suggest that Kupffer cell production of IL-10 is an important mechanism that down-regulates TNF production during liver regeneration.