Given the clinical significance of hepatitis B e antigen (HBeAg) seroconversion in chronic hepatitis B virus (HBV) infection, it is critical to elucidate the mechanisms regulating this process. In the present study, we found that the frequency of circulating chemokine (C-X-C motif) receptor 5 (CXCR5)+CD4+ T cells was higher in patients who had achieved HBeAg seroconversion in both cross-sectional ( P < 0.001) and longitudinal ( P = 0.009) studies. These cells were able to produce a significantly higher level of intracellular interleukin 21 (IL-21) after stimulation with HBV peptides in patients with telbivudine-induced HBeAg seroconversion ( P = 0.007). Furthermore, sorted CXCR5+CD4+ T cells from HBeAg seroconverters boosted a higher frequency of antibody against hepatitis B e antigen (anti-HBe)-secreting B cells in coculture assay ( P = 0.011). Of note, the increase in frequency of anti-HBe-secreting B cells was abrogated by soluble recombinant IL-21 receptor-Fc chimera ( P = 0.027), whereas exogenous recombinant IL-21 enhanced this effect ( P = 0.043). Additionally, circulating CXCR5+CD4+ T cells shared similar phenotypic markers, and were positively correlated in frequency with, splenic follicular T helper cells. Conclusion : Circulating CXCR5+CD4+ T cells, by producing IL-21, may have a significant role in facilitating HBeAg seroconversion in patients with chronic HBV infection. (Hepatology 2013;58:1277–1286)

The serological hallmark of primary biliary cirrhosis (PBC) is the presence of high titer and specific antimitochondrial antibodies (AMAs). Although there is no global immune defect in patients with PBC, there is widespread dysregulated B‐cell function, including increased sera levels of immunoglobulin M and enhanced B‐cell responses to cytosine‐phosphate‐guanine stimulation. The mechanisms involved in this B‐cell dysfunction have remained unknown. To address this issue, we focused on identifying the frequencies of B‐cell subsets in patients with PBC and the mechanisms that lead to B‐cell dysregulation, including the relationships with chemokine (C‐X‐C motif) receptor 5 (CXCR5)⁺CD4⁺T cells. Herein, we report that elevations of both serum and intrahepatic interleukin‐21 (IL‐21) were found in patients with PBC and, in particular, promoted B‐cell proliferation, signal transducer and activator of transcription 3 phosphorylation and AMA production in vitro. More important, upon stimulation with recombinant E2 subunit of pyruvate dehydrogenase complex, CXCR5⁺CD4⁺T cells in PBC produced higher levels of IL‐21 than healthy controls. Additionally, sorted CXCR5⁺CD4⁺T cells increased production of AMAs by autologous CD19⁺B cells. Indeed, elevated expression of intrahepatic chemokine (C‐X‐C motif) ligand 13 (CXCL13), a key chemokine of CXCR5⁺ cells, was uniquely found within the portal tracts in PBC, accompanied by infiltrates of CD4⁺, CXCR5⁺, CD19⁺, and CD38⁺ cells. Conclusion: CXCL13 promotes aggregation of CD19⁺B cells and CXCR5⁺CD4⁺T cells, which directs the aberrant AMA response by IL‐21. These data have implications for potential immunotherapy and also reflect the unique lymphoid biology in liver of PBC. (Hepatology 2015;61:1998‐2007)

Background and Aims: Cancer stem cells (CSCs) contribute to therapy resistance in HCC. Linear ubiquitin chain assembly complex (LUBAC) has been reported to accelerate the progression of cancers, yet its role in the sorafenib response of HCC is poorly defined. Herein, we investigated the impact of LUBAC on sorafenib resistance and the CSC properties of HCC, and explored the potential targeted drugs. Approach and Results: We found that HOIL-1, but not the other components of LUBAC, played a contributing role in LUBAC-mediated HCC sorafenib resistance, independent of its ubiquitin ligase activity. Both in vitro and in vivo assays revealed that the upregulated HOIL-1 expression enhanced the CSC properties of HCC. Mechanistically, HOIL-1 promoted sorafenib resistance and the CSC properties of HCC through Notch1 signaling. Mass spectrometry, co-immunoprecipitation, western blot, and immunofluorescence were used to determine that the A64/Q65 residues of HOIL-1 bound with the K78 residue of Numb, resulting in impaired Numb-mediated Notch1 lysosomal degradation. Notably, pixantrone was screened out by Autodock Vina, which was validated to disrupt HOIL-1/Numb interaction to inhibit Notch1 signaling and CSC properties by targeting the Q65 residue of HOIL-1. Moreover, pixantrone exerted synergistic effects with sorafenib for the treatment of HCC in different HCC mouse models. Conclusions: HOIL-1 is critical in promoting sorafenib resistance and CSC properties of HCC through Notch1 signaling. Pixantrone targeting HOIL-1 restrains the sorafenib resistance and provides a potential therapeutic intervention for HCC.