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Rheumatology Advance Access originally published online on May 30, 2006
Rheumatology 2007 46(1):37-43; doi:10.1093/rheumatology/kel174
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B-Lymphocyte stimulator (BLyS) up-regulation in mixed cryoglobulinaemia syndrome and hepatitis-C virus infection

M. Fabris1, L. Quartuccio1, S. Sacco1, G. De Marchi1, G. Pozzato2, C. Mazzaro3, G. Ferraccioli4, T. S. Migone5 and S. De Vita1

1Division of Rheumatology, DPMSC, School of Medicine, University of Udine, 2Internal Medicine, UCO, University of Trieste, 3Division of Internal Medicine 2, S. Maria degli Angeli Hospital, Pordenone, 4Department of Rheumatology, UCSC, School of Medicine, Catholic University of Rome, Italy and 5Human Genome Sciences, Rockville, MD, USA.

Correspondence to: Prof. S. De Vita, Chief, Clinic of Rheumatology, DPMSC, University of Udine, 33100 Udine, Italy. E-mail: salvatore.devita{at}med.uniud.it


   Abstract
Top
 Abstract
Introduction
 Methods
 Results
 Discussion
 Acknowledgements
 References
 
Objectives. To investigate the role of B-Lymphocyte stimulator (BLyS) in mixed cryoglobulinaemia syndrome (MCsn), a systemic vasculitis associated with a high risk to develop lymphoma, since BLyS up-regulation may favour both autoimmunity and lymphoproliferation.

Methods. BLyS serum levels were analysed by enzyme-linked immunosorbent assay (positive when >0.85 ng/ml) in 66 patients with MCsn, 54 (81.8%) of whom were positive for hepatitis-C virus (HCV) infection. Thirty-three HCV-positive patients without MCsn were also studied. Patients were compared with 48 healthy blood donors (HBDs). BLyS modifications after antiviral therapy were also studied.

Results. A significantly higher frequency of BLyS serum positivity was detected both in MCsn patients and in HCV-positive patients without MCsn (37.9 and 30.3%, respectively) when compared with HBDs (4.2%) (P < 0.0001 vs MCsn and P = 0.0026 vs HCV-positive patients without MCsn, respectively). BLyS appeared significantly higher in MCsn (3.70 ± 2.97 ng/ml) than in HCV-positive patients without MCsn (1.56 ± 0.63 ng/ml; P = 0.0044). BLyS expression did not correlate with rheumatoid factor levels, cryoglobulin levels or definite MCsn-related systemic features. High BLyS levels were significantly associated only with MCsn-related overt lymphoproliferative disorder. Finally, antiviral treatment significantly increased BLyS levels, independently from HCV-RNA negativization. However, BLyS normalization was noticed after both HCV-RNA negativization and suspension of antiviral therapy by preliminary data.

Conclusions. BLyS is up-regulated and may play a pathogenetic role in a fraction of patients with MCsn, similarly to other autoimmune diseases. HCV infection likely represents the early event leading to BLyS up-regulation in this setting. BLyS is up-regulated during antiviral treatment. Overall, these data provide new insights for BLyS and virus-related autoimmunity, lymphoproliferation and possible treatment strategies.

KEY WORDS: BLyS, BAFF, cryoglobulinemia, HCV, rheumatoid arthritis, SLE, Sjögren's syndrome


   Introduction
Top
 Abstract
 Introduction
Methods
 Results
 Discussion
 Acknowledgements
 References
 
Mixed cryoglobulinaemia syndrome (MCsn) is a systemic vasculitis prevalently mediated by immune complexes, i.e. mixed cryoglobulins, and characterized by non-neoplastic B-cell lymphoproliferation favouring the progression into frank B-cell non-Hodgkins lymphoma (NHL) in 5–10% of patients [1–3]. Cryoglobulins are formed by cold precipitable immunoglobulins, immune complexes formed by a rheumatoid factor (RF), usually immunoglobin M with k light chain (IgMk), monoclonal in type II, polyclonal in type III MC, that binds polyclonal immunoglobin G (IgG).

The hepatitis-C virus (HCV) infection is the aetiological agent in the large majority of MCsn cases [4, 5], and chronic antigenic stimulation by HCV is considered a key mechanism sustaining the proliferation of the RF-secreting B-cell clones [6]. Cryoglobulins are detected in up to 40% of HCV-positive subjects, with MCsn in 1–5%. In the minority of HCV-negative MCsn cases, other infectious agents or autoimmune and lymphoproliferative conditions [e.g. hepatitis-B virus (HBV) and Sjögren's syndrome (SS)] may be present [2, 7]. Besides chronic antigenic stimulation, cytokines and growth factors may also play a key role in sustaining B-cell overactivation in this settings, though limited data are available at present [2, 8, 9].

Recently, a new member of the tumour necrosis factor (TNF) superfamily called B-Lymphocyte stimulator (BLyS) was reported to be highly expressed in autoimmune diseases characterized by B-cell overactivation, such as systemic lupus erythematosus (SLE), SS and rheumatoid arthritis (RA) [10–13], all pre-disposing to NHL development [14]. Abnormal production of BLyS disturbs immune tolerance by allowing the survival of autoreactive B-cells, thus triggering autoimmune disorders [15–17]. BLyS acts essentially by inhibiting B-cell apoptosis [15], and B-cell apoptosis is implicated in the pathogenesis of MCsn [18] as well as of SS [19], RA [20] and SLE [21].

BLyS is expressed by monocytes, dendritic cells, T-cells, neutrophils and synoviocytes [22–26], and it acts on mature B-lymphocytes promoting differentiation, proliferation, survival (through Bcl2 up-regulation) and finally determining an increase in Ig-secreting cells [15, 16]. BLyS transgenic mice develop a lupus-like syndrome, followed by sialoadenitis and B-cell salivary gland infiltration and finally a B-cell lymphoma [17].

No data are available regarding BLyS either in MCsn or in the course of HCV infection.

In the present study, significantly increased BLyS serum levels were demonstrated in MCsn. Of note, BLyS appeared also up-regulated in HCV-infected patients without MCsn. Then, HCV infection may represent an early pathogenetic event leading to BLyS overexpresssion. Such novel information may be relevant when exploring BLyS de-regulation in autoimmune diseases of unknown aetiology [14]. Interestingly, BLyS up-regulation during antiviral treatment and BLyS normalization after HCV-RNA negativization and treatment suspension were also noticed in preliminary studies.


   Methods
Top
 Abstract
 Introduction
 Methods
Results
 Discussion
 Acknowledgements
 References
 
Sixty-six consecutive unselected patients with MCsn, classified according to published criteria [27], all with serum cryoglobulins repeatedly positive (>0.05 g/l) and with clinical signs of frank vasculitis (purpura and/or nephritis and/or peripheral neuropathy), were studied. Patients were referred to three different reference centres for MCsn in the north-east of Italy. Fifty-four (81.8%) were positive for serum HCV-RNA by nested polymerase chain reaction (PCR) and for anti-HCV antibodies detected by enzyme-linked immunosorbent assay (ELISA) (Ortho Diagnostic Systems, Raritan, NJ, USA), tested according to published methods [6]. Among the 12 HCV-negative cases, four were affected by SS, diagnosed according to published criteria [28], one was positive for HBV surface Antigen (HBsAg) and HBV-DNA, while the seven remaining cases were truly essential MCsn cases. Among the four SS patients, two presented a salivary gland B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) and one a myoepithelial sialadenitis (MESA). At the time of blood collection, 58 of these patients were untreated or on very low doses of corticosteroids (≤7.5 mg/day of prednisolone in 18 patients); the remaining eight MCsn patients were on antiviral therapy with pegylated-interferon-{alpha} (PEG-IFN-{alpha}) plus ribavirin.

An additional group of 33 age- and sex-matched patients with chronic HCV infection was also studied. Nine of them, despite the presence of detectable mixed cryoglobulins in the serum, were negative for a symptomatic MCsn, thus were defined as asymptomatic MC (asMC). The remaining 24 patients were definitely negative for serum cryoglobulins in repeated tests but all had histologically proven hepatitis and all had been treated for at least 12 months with PEG-IFN-{alpha} plus ribavirin: 11 of them had shown viral response (serum HCV-RNA negativization). These 24 patients, called HCV-positive without MC, were analysed for BLyS serum levels immediately before starting antiviral therapy, after 7.4 ± 2.4 months (still under antiviral treatment), and finally 34 ± 13 months after antiviral therapy suspension. Finally, BLyS serum concentration was evaluated in 48 age- and sex-matched healthy blood donors (HBDs). Written, informed consent to be included in the study had been obtained from all the study subjects, according to the Declaration of Helsinki. The study design was approved by the local Institutional Review Boards. Demographic, clinical and biochemical characteristics of all the study groups are shown in Table 1.


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  		TABLE 1. Demographic and clinical features of the studied subjects

 
Serum samples obtained from peripheral blood of MCsn patients, HCV-positive patients without MCsn and HBDs were kept frozen at –80°C. BLyS levels were assessed by antigen-capture ELISA by Human Genome Sciences, Rockville, MD, USA. This new method based on a Fab capture reagent allows to avoid the previously described [11] possible interference of the RF. Serum samples were analysed at a final concentration of 7% matrix; the lower limit of quantitation of this assay in undiluted serum was 0.85 ng/ml of BLyS. Moreover, RF concentration was assayed by nephelometric measure following established procedures (positive if >20 IU/ml) [6]. The cryoglobulins were obtained by cold precipitation (4°C for 72–96 h), washed four times with cold PBS buffer (phosphate buffered saline, pH 7.4) and their immunochemical typing was done by immunofixation. Type II MC was defined when cryoglobulins were composed by monoclonal RF-IgMk and polyclonal IgG, while type III MC presents only polyclonal Igs [1, 2, 27].

Statistics
GraphPad Prism software (Science Inc. San Diego, CA, USA) and MedCalc software were used for the statistical analysis. Nominal data were analysed by chi-square analysis of contingency tables (Fisher's exact test with Woolf's approximation). Correlations were determined by the Spearman rank test. All the numerical data are reported as the mean with the S.D. or as the median with min–max range. P-values were considered significant if <0.05.


   Results
Top
 Abstract
 Introduction
 Methods
 Results
Discussion
 Acknowledgements
 References
 
BLyS in MCsn and in HCV-positivepatients without MCsn
The new ELISA method for BLyS detection employed estimated an average of 8% of HBDs with detectable cytokine (>0.85 ng/ml). Consistent with this data, only 2/48 (4.2%) of HBDs presented detectable BLyS serum levels. In contrast, among the 66 MCsn patients, 25 (37.9%) showed detectable serum BLyS, [odds ratio (OR) = 14.02; confidence interval (CI) = 3.13–62.91, P < 0.0001 vs HBDs; Fig. 1A], with a mean value of 3.70 ± 2.97 ng/ml (Fig. 1B). HCV-positive and HCV-negative MCsn patients did not differ either in the percentage of BLyS positivity (37 vs 41.7%) or in BLyS serum levels (3.87 ± 3.15 ng/ml vs 3.01 ± 2.27 ng/ml). Notably, 10/33 (30.3%) of the patients with chronic HCV infection without MCsn (including nine patients with asMC and 24 HCV-positive without MC) also presented positive BLyS serum levels (OR = 10; CI = 2.021–49.48, P = 0.0026 vs HBDs), but the levels were significantly lower (1.56 ± 0.63 ng/ml) than those found in MCsn (P = 0.0044) (Fig. 1A and B). Among the nine asMC patients, only two (22.2%) presented positive BLyS levels (mean 1.37 ± 0.43 ng/ml). When taking 2.82 ng/ml (i.e. mean + 2S.D. of the levels found in HCV-positive patients without MCsn) as the cut-off level to define ‘high’ BLyS serum levels, we found 10/66 (15.2%) MCsn patients with ‘high’ BLyS levels, and two of them were HCV-negative (Fig. 1B, arrows).


Figure 1
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  		FIG. 1. BLyS serum levels in patients with MCsn, HCV-positive without MCsn (HCV+ w/o MCsn) and in HBDs: (A) Compared with HBDs, BLyS positivity (i.e. >0.85 ng/ml, black part of the bars) was significantly more frequent both in MCsn patients (*P < 0.0001) and in HCV-positive patients without MCsn (**P = 0.0026). BLOQ: below the level of quantitation, i.e. <0.85 ng/ml. (B) BLyS-positive cases and levels are shown. Horizontal bold lines represent the mean levels. BLyS levels were significantly higher in MCsn patients than in HCV-positive patients without MCsn (***P = 0.0044). Five out of 12 (41.7%) HCV-negative MCsn patients showed positive (>0.85 ng/ml) BLyS levels and two of them (arrows) showed ‘high’ BLyS levels (>2.82 ng/ml; see text).

 
To exclude that punctual analysis might not be really representative of the general situation, repeated measures of serum BLyS were performed in follow-up sera available from nine MCsn patients. As illustrated in Table 2, a very limited variability was noticed.


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  		TABLE 2. Repeated assessment of BLyS serum levels in nine MCsn patients

 
Low-dose corticosteroid therapy (prednisolone 5–7.5 mg/day) did not seem to influence BLyS expression, since 7/18 (38.9%) of the MCsn patients on corticosteroids at the time of blood collection presented positive levels.

Among the eight MCsn patients undergoing antiviral treatment at the time of blood collection, four (50%) presented positive serum BLyS levels (mean value 2.67 ± 1.7 ng/ml; range 1.55–5.2).

No significant correlation between RF or cryoglobulin serum concentrations and BLyS positivity or levels was found (data not shown).

Finally, a similar BLyS expression was found in males and females in the whole series of patients and controls (data not shown).

BLyS and the clinical manifestations in MCsn patients
None of the different systemic features that characterize MCsn (purpura, skin ulcers, arthritis/arthralgia, nephritis, peripheral neuropathy, or SS) was significantly associated with BLyS serum positivity or levels in the studied patients (data not shown). BLyS positivity was similar in MCsn patients with either type II or type III cryoglobulins (36.8 and 44.4%, respectively), even if the mean BLyS serum levels appeared slightly more elevated in type II (3.99 ± 3.16 ng/ml in type II vs 2.16 ± 0.18 ng/ml in type III; P = ns).

However, eight out of the 15 (53.3%) MCsn patients with a clinically overt lymphoproliferative disorder (LPD; nine cases of malignant B-cell NHL by histopathology and six cases lacking clear-cut pathological features of NHL by histopathology but showing clinical features highly suggestive for LPD, i.e. B symptoms, splenomegaly or persistent lymphadenopathy) showed positive BLyS serum levels (mean 5.05 ± 3.39 ng/ml). Five of them (33.3%) had high BLyS levels (>2.82 ng/ml). BLyS positivity was documented in 3/3 of the HCV-negative MCsn cases with SS and concomitant salivary MALT lymphoma or MESA.

MCsn patients without overt LPD showed positive BLyS in 17/51 (33.3%, P = ns vs MCsn with overt LPD), while high BLyS levels were found in 5/51 (9.8%). Thus, high BLyS levels were significantly more prevalent in patients with MCsn-related overt LPD than in MCsn patients without overt LPD (OR = 4.6, CI = 1.12–18.96, P = 0.040).

Among the four HCV-negative patients with SS-associated MCsn, positive BLyS was detected in three cases (mean 3.66 ± 2.87 ng/ml; with high BLyS levels in 2/3), i.e. in the only SS cases with a concomitant overt LPD (two B-cell salivary gland lymphomas of MALT and one MESA).

Antiviral therapy up-regulates BLyS serumlevels in HCV-positive patients
Sera from 24 HCV-positive patients without MC treated with IFN-{alpha} plus ribavirin were tested for serum BLyS both at baseline and after 7.4 ± 2.4 months, while all the patients were still undergoing antiviral therapy. Notably, BLyS serum levels were detectable in 8/24 (33.3%) of the pre-therapy samples and in 17/24 (70.8%) of the during-therapy samples (OR = 4.86, 95% CI = 1.43–16.50; P = 0.0199) (Table 3). The mean BLyS values at baseline were lower (1.61 ± 0.69 ng/ml) than those during therapy (2.73 ± 1.28 ng/ml; P = 0.0183). In particular, 7/8 patients with positive BLyS levels at baseline increased their BLyS titre about two times (2.17 ± 2.42, median 1.7), while one patient became BLyS-negative. Among the 16 patients negative for BLyS at baseline, 10 developed positive BLyS during antiviral therapy (Table 3).


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  		TABLE 3. Effects of antiviral therapy on BLyS serum levels in HCV-positive patient without MC

 
BLyS levels were then analysed with regard to the eradication of the HCV infection (HCV-RNA undetectable in the serum) during antiviral therapy. Serum BLyS was up-regulated in a similar manner in eradicated (11/24) and non-eradicated (13/24) patients: from 1.52 ± 0.47 ng/ml to 2.99 ± 1.45 ng/ml in HCV-eradicated patients and from 1.76 ± 1.08 ng/ml to 2.49 ± 1.14 ng/ml in non-eradicated patients. Thus, antiviral therapy with IFN-{alpha} plus ribavirin increased BLyS serum levels independent of the concomitant virus clearance.

Additional follow-up sera were available in seven HCV-RNA-eradicated patients, and were assayed for BLyS serum levels 34 ± 13 months (range: 13–51 months) after antiviral therapy discontinuation (all of them, even if HCV-RNA-negative at month +6, completed 12 months of IFN-{alpha} plus ribavirin treatment). As shown in Table 3, patients being BLyS-negative both at baseline and during antiviral therapy remained negative even at the last follow-up (2/2 cases). As concerns the patients who were BLyS-positive (two cases) or BLyS-negative (three cases) at baseline, and who either increased BLyS levels or became BLyS positive during antiviral therapy, they all became BLyS-negative at the last follow-up. Thus, by such preliminary studies, the effects of antiviral therapy appeared reversible, and HCV-RNA negativization was accompanied by BLyS normalization after treatment suspension.


   Discussion
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
Acknowledgements
 References
 
In the present study, BLyS deregulation was implicated for the first time in MCsn, an autoimmune and lymphoproliferative B-cell disorder in which HCV infection represents the usual aetiological agent [1–5]. HCV infection, in the lack of MCsn, was also associated, for the first time, with increased BLyS, consistent with a role of HCV as a trigger for BLyS up-regulation in about one-third of infected patients, possibly predisposing to B-cell proliferation and to the development of MCsn.

BLyS was recently described as a critical survival factor for B-cells, promoting their activation and maturation [17]. In humans, BLyS overexpression is increased in SLE, RA and SS, though only in a fraction of patients [10–13]. In contrast with the latter diseases, however, a definite viral trigger of B-cell hyperactivation and autoimmunity has been clearly identified in MCsn, i.e. HCV [2, 4, 5]. Then, when considering the currently accepted models of autoimmunity and lymphoproliferation triggered by infectious agents [14], present data identify the infectious event as an early step in which BLyS de-regulation may originate. In the light of this, BLyS would also represent a link between infection, autoimmunity and lymphoproliferation.

Interestingly, positive BLyS levels were also found in sera of HCV-unrelated MCsn patients, who represent a small minority of MCsn series [2]. It is possible that other infectious agents might be implicated in HCV-negative MCsn [2], sharing similar pathogenetic pathways with HCV also for what concerns BLyS de-regulation.

BLyS is also relevant in B-cell neoplastic diseases, where it acts as an essential autocrine survival factor, consistent with the elevated BLyS serum levels detected in this setting [29–32].

Compared with HBDs, positive BLyS serum levels were detected in a much higher percentage of MCsn patients as well as in HCV-infected patients without MCsn (with or without serum cryoglobulins). Why such an increase is limited to a fraction of MCsn and HCV-positive cases is unknown. Since increased BLyS was also reported only in a portion of patients with RA, SLE and SS [11–13], individual genetic predisposition to BLyS up-regulation or the fluctuation of BLyS serum levels over time in the same subject may be hypothesized. By the analysis of follow-up sera and in accordance with previous data in SLE [33], present results seem to exclude the second hypothesis. Thus, each patient seems to have a relatively stable BLyS phenotype. BLyS expression could be then induced (by HCV infection or by other pathogenetic events in HCV-negative cases) in a subset of predisposed individuals, possibly favouring the development of autoimmune and lymphoproliferative features in some of them in the follow-up. The mechanisms implicated for BLyS up-regulation in the course of HCV infection (e.g. enhanced activation of myeloid lineage and T-cells or additional sources) deserve additional investigation, and other viral or bacterial infections should be studied as well. Data are very limited in other infectious disorders. The BLyS system has been recently linked to altered B-cell homeostasis in the course of Epstein Barr and HIV virus infection [34–36].

A large spectrum of MCsn patients was studied, showing quite different patterns of organ involvement. MCsn patients affected by an overt LPD showed high BLyS levels more frequently than MCsn cases without LPD (P = 0.04), consistent with the reported association between BLyS and lymphoproliferation [29–32]. Overall, however, neither BLyS positivity nor high BLyS levels were significantly associated with any of the systemic MCsn features in the present series, since similar results were also reported in SLE [33], SS [37] and RA patients [38], BLyS appears to be linked to the disease itself rather than to peculiar organ manifestations.

Regarding HCV-related MCsn, HCV infection may be the critical event leading to BLyS elevation, rather than other biological events occurring at the step of the appearance of serum cryoglobulins or at the step of overt MC syndrome vasculitis [2, 39]. In this light, BLyS would play a role as an early, chronic ‘background’ stimulus for B-cell autoimmunity and lymphoproliferation in a subgroup of HCV-infected individuals.

The biological meaning of the higher BLyS levels detected in MCsn deserves additional investigation. They may either represent an epiphenomenon of the development of MCsn (e.g. expanded B-cell clones in MCsn, a prelymphomatous condition, may secrete BLyS) or an intrinsic characteristic of patients with MCsn, possibly favouring the development of MCsn itself. Alternatively, endogenous IFNs response to viral infection may increase BLyS [22]. It was seen from the preliminary data in 40 MCsn patients from the present series that patients with positive BLyS tended to have more elevated IFN-{gamma} levels than BLyS-negative subjects (data not shown), while serum IFN-{gamma} was detected in nearly all cases.

We did not find any correlation between BLyS expression and cryoglobulin or RF serum concentrations. This contrasts with some results on RF titre in RA and on anti-DNA and anti-SSA antibody titres in SLE and SS [10, 13, 33, 40], but is in accordance with other recent works [11, 37, 38]. The new ELISA method used in this study has been shown to efficiently eliminate RF interference for the detection of BLyS (Human Genome Sciences, personal communication), so this putative artefact can be ruled out. Secondly, the lack of correlation between BLyS and autoantibody titres is still consistent with the herein proposed hypothesis whereby BLyS is an early ‘background’ stimulus for B-cell survival and proliferation while other biological factors may further drive B-cell overactivity and autoantibody production.

While the aetiological role of chronic infection is well-established in MCsn, such information is lacking in SLE, RA and SS, where the role of a putative infectious trigger may be also transient, leading to a secondary fully-self-perpetuating autoimmune response. In this light, present results that better dissect the early role of infection as a possible mechanism for BLyS induction, before the development of the autoimmune response (e.g. positivization of serum cryoglobulins) and the overt autoimmune disease (e.g. MCsn) are of interest [14].

Once the relationship between HCV infection and BLyS overexpression is indicated, other steps become crucial, e.g.: (i) to investigate the cellular and molecular mechanism and the genetic basis of such BLyS up-regulation; (ii) to search for the second-step events leading to MCsn development and (iii) to link the results of antiviral therapy to BLyS expression. Preliminary data on the last issue were reported. Treatment of HCV-infected patients with IFN-{alpha} plus ribavirin was accompanied by an increase in serum BLyS, and this effect was independent from the concomitant eradication of the virus. IFN-{alpha}, rather than ribavirin, may lead to BLyS increase [22]. Furthermore, by preliminary data, the effects of antiviral therapy appeared reversible. In addition, BLyS positivity detected at the step of chronic viral infection (untreated) was followed by BLyS negativization long after the suspension of antiviral therapy in 2/2 long-term responders (i.e. persistently HCV-RNA-negative after treatment). IFN therapy can be effective in HCV-related MCsn, mainly in patients becoming HCV-RNA-negative [2]. However, MCsn patients may also show persistently active disease despite viral RNA negativization [41] and continue to present positive RF and cryoglobulins in most cases, i.e. the autoimmune and lymphoproliferative disorder persists. Finally, some MCsn manifestations as neuropathy, nephritis and skin ulcers may worsen [42], and the onset of MC was reported after IFN therapy to cure HCV infection [43]. The possibility that BLyS up-regulation might in part contribute to these effects in predisposed individuals should be then considered. BLyS may favour the survival of RF-positive B-cells, which may undergo antigen stimulation by different immune complexes also in the lack of the original trigger HCV [44].

In conclusion, BLyS is upregulated and may play a pathogenetic role in a fraction of patients with MCsn. HCV infection likely represents an early event leading to BLyS upregulation in this setting. Such novel information may be relevant also when exploring BLyS deregulation in autoimmune diseases of unknown aetiology, such as RA, SLE and SS.

Formula


   Acknowledgements
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Acknowledgements
References
 
The study was supported by ‘Società Italiana di Reumatologia’ (SIR) and ‘Ministero Italiano della Salute’.

Funding to pay the Open Access publication charges for this article was provided by the Rheumatology Clinic, DPMSC, University of Udine, Udine, Italy.

The authors have declared no conflicts of interest.


   References
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Acknowledgements
 References
 

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Submitted 10 January 2006; revised version accepted 18 April 2006.
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