Clonal CD27+ CD19+ B cell expansion through inhibition of FCγIIR in HCV+ cryoglobulinemic patients: A model

Valli De Re, Alessandro Pavan, Silvia Sansonno, Domenico Sansonno, Vito Racanelli

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Persistent HCV infection may be associated with extrahepatic manifestations such as type II mixed cryoglobulinemia (II-MC), a clonal B cell proliferative disorder. In persistent HCV infection without II-MC, an increase in serum immunoglobulins (Ig) is commonly observed. This increase is polyclonal and is determined primarily by increased levels of IgG which include both HCV-specific and nonspecific antibodies. Nonetheless, memory CD27+ B cells do not accumulate. This paradoxical phenomenon depends on heightened sensitivity of memory B cells to BCR-independent noncognate T cell help, which speeds up their terminal differentiation into antibody-secreting cells and makes them more prone to apoptosis. In persistent HCV infection with II-MC, serum Ig elevation is also a general occurrence, and characteristically includes IgM antibodies with rheumatoid factor activity, which are essential for the development of circulating, cryoprecipitable immune complexes. Hypergammaglobulinemia is sustained by a peripheral expansion of IgM+k+IgD low/negCD21lowCD27+ B cells. These cells exhibit marked VH, JH, and VK gene segment usage restriction, indicating that a limited number of antigens drive their proliferation through BCR interaction. Recently, two epitopes, one of the human IgG and the second of the HCVNS3 protein, had been identified and demonstrated able to link the BCR exposed on II-MC subjects. Based on the above findings, we propose a model whereby BCR binding the IgM/IgG/HCVNS3 immune complexes deprives FcγIIR of its natural ligand. This takes the brake off RF+CD27+ B cell proliferation and promotes their selective accumulation, which is otherwise prevented by increased apoptosis susceptibility in persistent HCV infection without II-MC.

Original languageEnglish
Title of host publicationAnnals of the New York Academy of Sciences
Pages326-333
Number of pages8
Volume1173
DOIs
Publication statusPublished - Sep 2009

Publication series

NameAnnals of the New York Academy of Sciences
Volume1173
ISSN (Print)00778923
ISSN (Electronic)17496632

Keywords

  • B cell clonal expansion
  • B cell receptor (BCR)
  • Cryoglobulinemia
  • FC gamma II receptor (FCγIIR)
  • Hepatitis C virus (HCV)

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)

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