Clonal B cells of HCV‐associated mixed cryoglobulinemia patients contain exhausted marginal zone‐like and CD21^low cells overexpressing Stra13

Abstract

A clonal population of B cells expressing a V H 1-69-encoded idiotype accumulates in hepatitis C virus (HCV) associated mixed cryoglobulinemia (MC). These cells are phenotypically heterogeneous, resembling either typical marginal zone (MZ) B cells (IgM +IgD IntroductionHepatitis C virus (HCV) is associated with a spectrum of extrahepatic manifestations, the best characterized of which is type II mixed cryoglobulinemia (MC) [1]. MC is a benign monoCorrespondence: Dr. Massimo Fiorilli e-mail: massimo.fiorilli@uniroma1.it clonal lymphoproliferative disorder of B cells producing rheumatoid factor IgM that, in turn, forms cryoprecipitable immune complexes leading to small vessel vasculitis in vivo [1]. In a large proportion of MC patients, the monoclonal rheumatoid factor bears an idiotype encoded by the V H 1-69 heavy chain variable gene [2,3]. Several lines of evidence suggest that HCV activates B cells via the cross-reactivity of the V H 1-69-encoded idiotype with the E2 glycoprotein of the viral envelope [4,5] The CD21 low B cells expanded in CVID, in HCV + MC, and in HIV-infected patients as well as those found in the tonsil show signs of previous activation and proliferation, fail to proliferate in response to B-cell stimuli and are unable to flux calcium upon BCR cross-linking, although they are in general poised to secrete high levels of immunoglobulins [11][12][13][15][16][17][18][19][20]. In addition, CD21 low B cells express a peculiar array of homing and inhibitory receptors, the latter including CD22, CD72, CD32b, CD85j, CD85d, Fc receptor-like 4 (FCRL4), and sialic acid binding Ig-like lectin 6 (Siglec-6) [11,[15][16][17][18][19][20]. The contribution of these inhibitory receptors, and particularly of FCRL4 and Siglec-6, to the dysfunction of CD21 low B cells is supported by the partial recovery of the proliferative capacity and of effector function upon silencing of these genes with siRNA [21].We recently suggested that the CD21 + MZ-like V H 1-69 + B cells of MC patients also fail to proliferate in response to TLR9 ligation [13]. Here, we characterized the responses of these cells to B-cell stimuli and investigated inhibitory mechanisms. We show that MZ-like V H 1-69 + B cells are functionally exhausted since they fail to respond to TLR and BCR ligands, although their proliferative defect can be overcome by co-stimulation of TLR9 and BCR in the presence of interleukin(IL)-2 and IL-10. In addition, MZ-like V H 1-69 + B cells display increased constitutive and decreased BCRinduced phosphorylation of extracellular signal regulated kinase (ERK); this pattern, however, was also observed in a subpopulation of MZ B cells from healthy individuals. Finally, although the CD21 + MZ-like V H 1-69 + B cells do not express the inhibitory receptors of CD21 low B cells, they strikingly overexpress Stra13, a transcriptional repressor that acts as a key negative regulator of activation and cell cycle progression in B cells [22][23][24]. Our results indicate that the V H 1-69 + MZ B cells activated by HCV undergo premat...

Persistence of a Large Population of Exhausted Monoclonal B cells in Mixed Cryoglobuliemia After the Eradication of Hepatitis C Virus Infection

“…It has been shown that circulating immune complexes are able to activate rheumatoid factor-producing murine B cells, especially in the presence of surrogate T cell help or when they contain nucleosome antigens [18]. We found that V H 1-69 + B cells do not proliferate in response to CpG alone or to the crosslinking of the B-cell receptor with anti-Ig alone, but costimulation with anti-Ig and CpG can elicit a proliferative response, although of low-level [19]. Thus, immune complexes containing DNA or RNA [20,21], such as those formed with microbial components or with nucleosomes, might provide a dual BCR/TLR stimulus capable to sustain low-level self-renewal of anergic MZ-like V H 1-69 + B cells.…”

“…Thus, lack of expression of these inhibitory receptors by anergic V H 1-69 + CD21 high MZ-like B cells is intriguing. However, we recently observed [19] that MZ-like V H 1-69 + B cells display constitutive over-expression of phosphorylated ERK and attenuated BCR signaling, a molecular signature of the anergy induced by continual BCR occupancy by antigen [25], and over-expression of the antiproliferative transcription factor Stra13.…”

T-bet+ B cells are induced by human viral infections and dominate the HIV gp140 response

“…We also observed involvement of T-bet + B cells in the response to HIV infection, as T-bet was rapidly induced in B cells during the acute phase and T-bet We and others have previously demonstrated an expansion of CD21 -B cell subsets induced by Th1-type human infections, including HIV, malaria, and hepatitis C (30,31,34,35,(60)(61)(62)(63), and expansion of a clonal CD21 -subset has been described during hepatitis B-and hepatitis C-associated mixed cryoglobulinemia (64)(65)(66). Interestingly, maintenance of expanded CD21 -cells in each of these infections appears to be dependent upon pathogen load (34,35,60,(67)(68)(69).…”

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

“…This is further supported by the specificity of the B-cell receptor of HCV-associated lymphomas for viral antigens, in particular the HCV protein E2 [6,7]. Accordingly, many monoclonal B cells in MC type II and HCV-associated B-cell lymphomas use the immunoglobulin variable (IgV) gene segment VH1-69, which is known to be used both by rheumatoid factors and by some E2-specific antibodies, further supporting a role of antigenic drive in HCV-associated B-cell expansion [8][9][10][11][12].…”

“…HCV-associated B-cell lymphomas use the immunoglobulin variable (IgV) gene segment VH1-69, which is known to be used both by rheumatoid factors and by some E2-specific antibodies, further supporting a role of antigenic drive in HCV-associated B-cell expansion [8][9][10][11][12]. A second pathogenetic mechanism of HCV on B cells may be a direct mutagenic effect of the virus, including induction of reactive oxygen species [13,14], and of activation-induced cytidine deaminase [15], which is the master regulator for somatic hypermutation of IgV genes and some other off-target genes [16].…”