Intrahepatic B-cell follicles of chronically hepatitis C virus-infected individuals lack signs of an ectopic germinal center reaction

Abstract

Chronic infection with hepatitis C virus (HCV) often affects the B-cell compartment, leading to the occurrence of autoimmunity and B-cell lymphoproliferation, in particular mixed cryoglobulinemia and B-cell lymphomas. HCV presumably causes these lymphoproliferations by chronic antigenic stimulation and/or direct mutagenic effects on B cells. It has been speculated that the interaction of HCV with B cells and the expansion of antigen-triggered B cells happens in germinal center-like structures in the livers of HCV carriers. We studied rearranged immunoglobulin V(H) genes from seven B-cell follicles microdissected from the livers of three unselected chronic HCV patients. The follicles consisted of polyclonal naive and memory B-cell populations with only rare indication of minor clonal expansions and no evidence for active somatic hypermutation. Frequent detection of V(H) rearrangements using the VH1-69 gene segment nevertheless indicated that at least a fraction of the B cells is HCV-specific and/or autoreactive. Thus, the typical intrahepatic B-cell follicles in chronic HCV carriers do not function as ectopic germinal centers for clonal expansion and affinity maturation of B cells. Hence, autoreactive and HCV-specific B-cell clones might either develop in secondary lymphoid organs or in intrahepatic follicles only under particular, yet undefined, circumstances.

Keywords: B-cell clonal expansion; Germinal centers; HCV; IgVH genes; Somatic hypermutation.