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Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is comparable to multiple sclerosis, diabetes or rheumatoid arthritis in prevalence (∼0.2% to 1%), long-term disability, and quality of life,[1–5] yet the scale of biomedical research and funding has been pitifully limited, as the recent National Institutes of Health (NIH) and Institute of Medicine reports highlight.[6,7] Recently in the USA, NIH Director Francis Collins has stated that the NIH will be ramping up its efforts and levels of funding for ME/CFS,[8] which we hope will greatly increase the interest in, and resources for researching this illness. Despite scant funding to date, researchers in the field have generated promising leads that throw light on this previously baffling illness. We suggest the key elements of a concerted research programme and call on the wider biomedical research community to actively target this condition.

It is widely perceived that there is a problem in giving a naturalistic account of mental representation that deals adequately with the issue of meaning, interpretation, or significance (semantic content). It is suggested here that this problem may arise partly from the conflation of two vernacular senses of representation: representation-as-origin and representation-as-input. The flash of a neon sign may in one sense represent a popular drink, but to function as a representation it must provide an input to a ‘consumer’ in the street. The arguments presented draw on two principles – the neuron doctrine and the need for a venue for ‘presentation’ or ‘reception’ of a representation at a specified site, consistent with the locality principle. It is also argued that domains of representation cannot be defined by signal traffic, since they can be expected to include ‘null’ elements based on non-firing cells. In this analysis, mental representations-as-origin are distributed patterns of cell firing. Each firing cell is given semantic value in its own right – some form of atomic propositional significance – since different axonal branches may contribute to integration with different populations of signals at different downstream sites. Representations-as-input are patterns of local co-arrival of signals in the form of synaptic potentials in dendrites. Meaning then draws on the relationships between active and null inputs, forming ‘scenarios’ comprising a molecular combination of ‘premises’ from which a new output with atomic propositional significance is generated. In both types of representation, meaning, interpretation or significance pivots on events in an individual cell. (This analysis only applies to ‘occurrent’ representations based on current neural activity.) The concept of representations-as-input emphasizes the need for an internal ‘consumer’ of a representation and the dependence of meaning on the co-relationships involved in an input interaction between signals and consumer. The acceptance of this necessity provides a basis for resolving the problem that representations appear both as distributed (representation-as-origin) and as local (representation-as-input). The key implications are that representations in the brain are massively multiple both in series and in parallel, and that individual cells play specific semantic roles. These roles are discussed in relation to traditional concepts of ‘gnostic’ cell types.

ObjectivesTo examine the expression of B-cell-activating factor receptor (BAFF-R) on naive CD27− and memory CD27+ B cells in normal individuals and patients with rheumatoid arthritis (RA) undergoing B-cell depletion therapy with rituximab.Patients and MethodsBAFF-R expression on B-cell subsets was determined in normal controls (NC; n=11), active patients with RA pre-rituximab (pre-RX; n=15), relapsing patients either concordant for B-cell repopulation (C-R, n=13) or discordant, with relapse more than 3 months after repopulation (D-R, n=11) and patients in remission over 3 months postrepopulation (discordant non-relapsing (D-NR), n=5). Serum BAFF was measured by ELISA and analysed using Mann–Whitney.ResultsThere was no significant difference between NC, pre-RX and D-NR patients in %BAFF-R-positive B cells or mean fluorescence intensity (MFI) in naive and memory B cells. Relapsing patients had significantly lower MFI and %BAFF-R-positive cells in both naive and memory compartments from NC and pre-RX (C-R and D-R; pConclusionBAFF-R expression was significantly reduced on both naive and memory B cells in patients at relapse, regardless of the relationship with B-cell repopulation or serum BAFF levels. Re-establishment of active disease was also associated with an increase in class-switch recombination. Factors responsible for lower levels of BAFF-R may relate to altered thresholds for autoreactive B-cell generation at relapse in patients with RA.

Objectives: To describe the long-term clinical outcome and safety profile of B cell depletion therapy (BCDT) in patients with systemic lupus erythematosus (SLE). It was also determined whether baseline parameters can predict the likelihood of disease flare. Methods: 32 patients with refractory SLE were treated with BCDT using a combination protocol (rituximab and cyclo-phosphamide). Patients were assessed with the British Isles Lupus Assessment Group (BILAG) activity index, and baseline serology was measured. Flare was defined as a new BILAG ‘A’ or two new subsequent ‘B’s in any organ system. Results: Of the 32 patients, 12 have remained well after one cycle of BCDT (median follow-up 39 months). BCDT was followed by a decrease of median global BILAG scores from 13 to 5 at 6 months (p = 0.006). Baseline anti-extractable nuclear antigen (ENA) was the only identified independent predictor of flare post-BCDT (p = 0.034, odds ratio = 8, 95% CI 1.2 to 55) from multivariable analysis. Patients with low baseline serum C3 had a shorter time to flare post-BCDT (p = 0.008). Four serious adverse events were observed. Conclusion: Autoantibody profiling may help identify patients who will have a more sustained response. Although the long-term safety profile of BCDT is favourable, ongoing vigilance is recommended.

B-cell depletion based on rituximab has now been proven to be an effective therapy for seropositive rheumatoid arthritis with a good safety profile. The encouraging results from early, open-label trials have been confirmed in three large, controlled trials. A license for use in patients that have failed antitumor necrosis factor-α agents has been obtained in the USA and is imminent in several other countries. Despite this welcome progress, experience suggests that all patients who respond to B-cell depletion eventually show clinical relapse. Possible mechanisms of relapse include incomplete depletion of pathogenic B cell clones, persistence of long-lived plasma cells producing pathogenic autoantibodies, or persistence of other kinds of cells, such as autoreactive T cells carrying ‘disease memory’. A better understanding of why patients relapse may allow us to optimize B-cell depletion protocols based on rituximab and/or other agents and contribute to the development of B-cell-targeted therapies, with the ...

B-cell-targeted therapy for autoimmune disease emerged from theoretical proposition to practical reality between 1997 and 1998, with the availability of the B-cell-depleting monoclonal antibody rituximab. Since then, a score of autoantibody-associated disorders have been treated, with most convincing evidence of efficacy seen in subjects with rheumatoid arthritis. Several classes of B-cell-targeted agent are now under investigation. From the outset, a major goal of B-cell targeting has been the re-establishment of some form of immunological tolerance. In some subjects, the observed improvement of disease for years following therapy fuels hope that this goal might ultimately be achievable.

An open-label study indicated that selective depletion of B cells with the use of rituximab led to sustained clinical improvements for patients with rheumatoid arthritis. To confirm these observations, we conducted a randomized, double-blind, controlled study.We randomly assigned 161 patients who had active rheumatoid arthritis despite treatment with methotrexate to receive one of four treatments: oral methotrexate (or =10 mg per week) (control); rituximab (1000 mg on days 1 and 15); rituximab plus cyclophosphamide (750 mg on days 3 and 17); or rituximab plus methotrexate. Responses defined according to the criteria of the American College of Rheumatology (ACR) and the European League against Rheumatism (EULAR) were assessed at week 24 (primary analyses) and week 48 (exploratory analyses).At week 24, the proportion of patients with 50 percent improvement in disease symptoms according to the ACR criteria, the primary end point, was significantly greater with the rituximab-methotrexate combination (43 percent, P=0.005) and the rituximab-cyclophosphamide combination (41 percent, P=0.005) than with methotrexate alone (13 percent). In all groups treated with rituximab, a significantly higher proportion of patients had a 20 percent improvement in disease symptoms according to the ACR criteria (65 to 76 percent vs. 38 percent, Por =0.025) or had EULAR responses (83 to 85 percent vs. 50 percent, Por =0.004). All ACR responses were maintained at week 48 in the rituximab-methotrexate group. The majority of adverse events occurred with the first rituximab infusion: at 24 weeks, serious infections occurred in one patient (2.5 percent) in the control group and in four patients (3.3 percent) in the rituximab groups. Peripheral-blood immunoglobulin concentrations remained within normal ranges.In patients with active rheumatoid arthritis despite methotrexate treatment, a single course of two infusions of rituximab, alone or in combination with either cyclophosphamide or continued methotrexate, provided significant improvement in disease symptoms at both weeks 24 and 48.

Objective To explore the changes in serologic variables and clinical disease activity following B lymphocyte depletion in 22 patients with rheumatoid arthritis (RA). Methods B lymphocyte depletion was attained using combination therapy based on the monoclonal anti-CD20 antibody rituximab. Levels of a serologic indicator of inflammation, C-reactive protein (CRP), of antimicrobial antibodies, of autoantibodies including IgA-, IgM-, and IgG-class rheumatoid factors (RF), and of antibodies to cyclic citrullinated peptide (anti-CCP) were assayed. Results The majority of patients showed a marked clinical improvement after treatment with rituximab, with benefit lasting up to 33 months. Levels of total serum immunoglobulins fell, although the mean values each remained within the normal range. Whereas the IgM-RF response paralleled the changes in total serum IgM levels, the levels of IgA-RF, IgG-RF, and IgG and anti-CCP antibodies decreased significantly more than did those of their corresponding total serum immunoglobulin classes. The kinetics for the reduction in CRP levels also paralleled the decreases in autoantibody levels. In contrast, levels of antimicrobial antibodies did not change significantly. B lymphocyte return occurred up to 21 months posttreatment. The time to relapse after B lymphocyte return was often long and unpredictable (range 0–17 months). Relapse was, however, closely correlated with rises in the level of at least one autoantibody. Increased autoantibody levels were rarely observed in the absence of clinical change. Conclusion Following B lymphocyte depletion in patients with RA, a positive clinical response occurred in correlation with a significant drop in the levels of CRP and autoantibodies. Antibacterial antibody levels were relatively well maintained. B lymphocyte return preceded relapse in all patients. There was also a temporal relationship between clinical relapse and rises in autoantibody levels. Although these observations are consistent with a role for B lymphocytes in the pathogenesis of RA, the precise mechanisms involved remain unclear.

Objectives An open study of B-lymphocyte depletion was undertaken in rheumatoid arthritis (RA) patients to test the hypothesis that B lymphocytes may be essential to disease perpetuation. Methods Five patients with refractory RA were treated with a monoclonal anti-CD20 antibody, cyclophosphamide and prednisolone and followed for 12-17 months. Patient 2 received further treatments at 8 and 12 months and patient 4 at 11 months. Results At 26 weeks all patients satisfied the American College of Rheumatology ACR50 and patients 1-3 the ACR70 criteria of improvement, without further therapy. Patients 1, 3 and 5 achieved ACR70 at 1 yr and rheumatoid factor (RF) levels fell to normal. In patients 3 and 5, B lymphocytes returned without relapse. Patient 2 relapsed at 28 weeks and patient 4 at 38 weeks, coincident with the return of B lymphocytes in the presence of raised RF levels. Both achieved ACR70 on retreatment. Adverse events were limited to respiratory episodes (two patients) and marginal thrombocytopenia (one patient). Conclusions These findings are consistent with the concept that RA is critically dependent on B lymphocytes and suggest that B-lymphocyte depletion may be a safe and effective therapy.

Normal immunological memory is thought to be underpinned by T lymphocytes. However, in rheumatoid arthritis there are indications that T-lymphocyte control has been subverted by self-perpetuating B lymphocytes. Potential mechanisms in other autoimmune states are less clear, but a number of observations suggest that misappropriation of immunological memory by B lymphocytes may be a common feature of human autoantibody-associated disease. Put simply, autoantibodies drive their own production. If so, the availability of safe B-lymphocyte-depleting agents provides a potential means for reversal of autoimmunity.

Objective Increased cardiovascular risk has been associated with high levels of serum antibodies to citrullinated proteins (ACPA) in patients with rheumatoid arthritis (RA). Citrullination is part of many chronic inflammatory processes and we therefore investigated whether ACPA might be associated with coronary artery disease, in the absence of RA. Methods To maximize the potential predictive value of this retrospective study we included sera from a cohort of 3052 healthy male individuals, subsequently followed for the development of coronary artery disease, and documented for other disease risk factors. With each case event (myocardial infarction; n = 144), 2 matched controls were assigned. Results We found 10.4% of cases were ACPA positive compared to 3.8% of controls (odds ratio (95% CI) = 3.26 (1.36–7.80), p = 0.008), remaining significant after adjustment for classical risk factors including smoking and CRP (4.23 (1.22–14.61) p = 0.02). Conclusion The genesis and fine specificity of ACPA in patients with atherosclerosis, in the absence of Rheumatoid arthritis, may prove worthy of further investigation.

OBJECTIVE: To investigate whether the incidence of secondary hypogammaglobulinaemia in patients with RA following rituximab was related to patterns of B-cell return and relapse. METHODS: CD19(+) B-cell and serum immunoglobulin (sIg) determinations were done every 2 or 3 months in 137 consecutive patients treated with one or more courses of rituximab-based B-cell depletion therapy. The pattern of B-cell return, either concordant or discordant with relapse, was also recorded. RESULTS: There were 119 responders. Before treatment, three patients had low IgM and four had low IgG. After the first cycle, low IgM or IgG was present in 9.2% (11/119) and 11.8% (14/119) of the patients, respectively, increasing to 38.8% (8/18) and 22.2% (4/18) after five cycles. The mean percent maximum sIg decrease/cycle was relatively constant. The CD19(+) B-cell count at repopulation was not correlated with immunoglobulin (Ig) levels after each cycle. Patients discordant for B-cell return and relapse developed significantly lower serum IgM and more low IgM episodes than concordant patients (P

An invited workshop on ‘Theories of Consciousness’ was organized in the format of a Nature Network closed group during the second semester of 2009. There were presentations by each of 15 authors active in the field, followed by debate with other presenters and invitees. A week was allocated to each of the theories proposed; general discussion threads were also opened from time to time, as seemed appropriate. We (who had been participants in the workshop) offer here an account of the principal outcomes. It can be regarded as a contemporary, ‘state of the art’ snapshot of thinking in this field.

Objective To describe the 6-month clinical outcome and the long-term safety profile of B cell depletion therapy (BCDT) in 50 patients with active systemic lupus erythematosus (SLE), who were nonresponsive or poorly responsive to conventional immunosuppression. Methods All except 4 of 50 patients with active SLE received 1 gm of rituximab, 750 mg of cyclophosphamide, and 100–250 mg of methylprednisolone, administered on 2 occasions 2 weeks apart, to achieve B cell depletion. Clinical outcome was assessed using the British Isles Lupus Assessment Group (BILAG) activity index and serial serologic measurements of disease activity. Remission was defined as a change from a BILAG A or B score to a C or D score in every organ system. Partial remission was a change from a BILAG A or B score to a C or D score in at least 1 system, but with the persistence of 1 score of A or B in another system. No improvement was defined as a BILAG A or B score that remained unchanged after treatment. Results Of the 45 patients available for followup at 6 months, 19 patients (42%) achieved remission, and 21 patients (47%) reached partial remission after 1 cycle of BCDT (mean followup 39.6 months). BCDT resulted in a decrease in median global BILAG scores from 12 to 5 (P < 0.0001) and median anti–double-stranded DNA antibody titers from 106 to 42 IU/ml (P < 0.0001), and an increase in the median C3 level from 0.81 to 0.95 mg/liter (P < 0.02) at 6 months. Five serious adverse events were observed. Conclusion BCDT is an effective treatment for patients with active SLE whose disease has failed to respond to standard immunosuppressive therapy. Although the safety profile of BCDT is favorable, ongoing monitoring is required.

Since the anti-CD20 therapeutic monoclonal antibody rituximab became available for clinical use in 1997 the effects of B lymphocyte depletion (BLyD) have been explored in a range of autoimmune disorders (Edwards et al., 2002). The results of a formal controlled trial in rheumatoid arthritis (RA) confirm that clinical benefit can be substantial (Edwards et al., 2004). Perhaps more significantly in the long term, the opportunity afforded by BLyD to study mechanisms underlying pathogenesis of many human autoimmune diseases is unique and exciting. This chapter reviews the rationale for BLyD in the context of changing ideas about the role of B cells in autoimmunity, and explores the emerging concept of autoimmune B cells as immunologic Trojan horses. The potential for clinical application, the logistics employed, and the clinical results obtained with rituximab so far are reviewed. Finally, evolving immunodynamic studies are described, which highlight correlations between clinical state and autoantibody profiles, and which may elucidate mechanisms of action and point to means of optimization of therapeutic benefit and development of further targeted approaches to therapy. © 2005 Springer Science+Business Media, Inc.

Objective To assess the effects of B lymphocyte depletion on serum B lymphocyte stimulator (BLyS; trademark of Human Genome Sciences, Rockville, MD) levels in patients with rheumatoid arthritis (RA), and to assess the relationship of serum BLyS levels with peripheral blood B cell depletion, levels of autoantibodies and antimicrobial antibodies, the return of peripheral blood B cells, and clinical relapse. Methods Fifteen patients with active RA underwent rituximab-based B cell depletion therapy (BCDT). Disease activity was assessed clinically, peripheral blood CD19+ B cell counts were determined by flow cytometry, and serum levels of BLyS, IgM, IgA, and IgG rheumatoid factors (RFs), anti–cyclic citrullinated peptide, and antimicrobial antibodies were assessed using enzyme-linked immunosorbent assays. Results Peripheral blood B cell depletion was achieved in all 15 patients, and an American College of Rheumatology 20% response was achieved in 13 patients. Following clinical relapse, 7 patients underwent at least 1 additional cycle of BCDT. In every case, serum BLyS levels markedly rose post-BCDT and remained elevated for at least 1–2 months. Serum levels of RF, but not those of anti–tetanus toxoid or anti–pneumococcal polysaccharide antibodies, fell significantly. A decline in serum BLyS levels was associated with the reemergence of B cells in peripheral blood, which, in turn, antedated clinical relapse by variable periods of time. The patterns of B cell depletion, serum BLyS and antibody levels, and clinical relapse for each BCDT cycle were remarkably similar in re-treated patients. Conclusion Rituximab-based BCDT leads to marked increases in serum BLyS levels. This may contribute significantly to the survival and/or regeneration of B cell populations capable of triggering clinical relapse.

Objective To study the quantitative and phenotypic reconstitution of peripheral blood B cells and its relationship to the dynamics of clinical response in patients with rheumatoid arthritis (RA) following B cell depletion with rituximab. Methods Twenty-four patients with active RA treated with rituximab were studied. Flow cytometry with combinations of monoclonal antibodies to B cell and T cell subsets was used. Results The frequency and total number of CD19+ cells in the peripheral blood decreased a mean of 97% for more than 3 months in all but 1 patient following rituximab therapy. All B cell populations were depleted. More than 80% of residual B cells showed a memory or plasma cell precursor phenotype. B cell repopulation occurred a mean of 8 months after treatment and was dependent on the formation of naive B cells, which showed an increased expression of CD38 and CD5. During repopulation, increased numbers of circulating immature B cells, CD19+,IgD+,CD38high,CD10low,CD24high cells, were identified. Patients who experienced a relapse of RA on return of B cells tended to show repopulation with higher numbers of memory B cells. A small number of T cells and natural killer cells expressed low levels of CD20. These cells were depleted following rituximab therapy and returned to the circulation a mean of 5 months after treatment. No other significant changes were detected in the T cell populations studied. Conclusion Rituximab induced a profound depletion of all peripheral blood B cell populations in patients with RA. Repopulation occurred mainly with naive mature and immature B cells. Patients whose RA relapsed on return of B cells tended to show repopulation with higher numbers of memory B cells.

Objectives: To report the clinical outcome and safety profile of repeated B cell depletion in seven patients with refractory systemic lupus erythematosus (SLE). Methods: Since June 2000, seven patients with refractory SLE had repeated cycles of B cell depletion (18 cycles in total, up to three cycles per patient) because of disease relapse. The clinical response (assessed by the British Isles Lupus Activity Guide (BILAG) activity index), duration of B cell depletion, and adverse events in these patients was reviewed. Results: Four patients (Nos 1, 2, 3, 6) had three cycles of treatment and three (Nos 4, 5, 7) had two cycles. Four of the seven patients (Nos 1, 3, 5, 6) improved. The mean global BILAG scores dropped from 15 to 6 at 5–7 months. The median duration of clinical response and B cell depletion was 13 months and 6 months, respectively. After the third cycle, 2/4 patients (Nos 1 and 2) improved. The median duration of clinical benefit was 12 months. Most patients tolerate re-treatment very well. Conclusion: Re-treatment with B cell depletion of patients with severe SLE is safe and may be effective for 6–12 months on average.

Background: During the 1990s evidence emerged to suggest that B lymphocyte depletion in rheumatoid arthritis (RA) might be of major benefit. Methods and Results: In 1997 the B lympholytic monoclonal

Objective To gain preliminary evidence for the safety and efficacy of B lymphocyte depletion therapy in refractory systemic lupus erythematosus (SLE). Methods Six female patients with active SLE, resistant to standard immunosuppressive therapy, were treated on an open-label basis. During a 2-week period, each patient received two 500-mg infusions of rituximab, two 750-mg infusions of cyclophosphamide, and high-dose oral corticosteroids. Results No significant adverse events were observed during followup. Patient 1 had not improved at 3 months but was then lost to followup. At 6 months, all 5 remaining patients had improved, as evidenced by improvement in British Isles Lupus Assessment Group global scores, from a median of 14 (range 9–27) at baseline to a median of 6 (range 3–8) at 6 months. Manifestations of SLE such as fatigue, arthralgia/arthritis, and serositis responded particularly well to this protocol. Hemoglobulin levels increased in patients 2, 3, 5, and 6. The erythrocyte sedimentation rate decreased in patients 2, 3, 4, and 5 and was stable in patient 1. In patients 4 and 5, the urinary protein–to-creatinine ratio decreased significantly. C3 serum levels increased in all 5 patients who had low levels at baseline; in two of these patients, patients 2 and 5, C3 values were normal at 6 months. The variation in the level of anti–double-stranded DNA antibody was different in individual patients. Conclusion This study provides sufficient evidence for the safety and possible efficacy of B lymphocyte depletion therapy in SLE to justify a formal controlled trial.

B cell depletion therapy (BCDT) has recently been used with success to treat patients with rheumatoid arthritis and systemic lupus erythematosus (SLE). As antiphospholipid antibodies have been implicated in the pathogenesis of the antiphospholipid syndrome (APS), we asked the question whether BCDT affects levels of IgG anticardiolipin antibodies (aCL) in our cohort of 32 SLE patients given this treatment.We identified seven SLE patients who had undergone BCDT and had had at least two moderate positive aCL titres at least 12 weeks apart. Of these only one patient had APS. IgG aCL were measured at time 0 and 6-9 months post BCDT.At time 0, the mean IgG aCL level was 20.6 standardized IgG antiphospholipid units (GPLU) (range (SD) 10-32, (10.1), normal level5). At 6-9 months post depletion the IgG aCL levels in six of the seven patients was undetectable and in the other patient the level reduced from 25 GPLU to 15 GPLU (p0.005, two-tailed paired t test). At baseline, only one patient had a mildly positive anti-beta(2)-glycoprotein I (beta(2)GPI) antibody level at 30% (compared to an in-house standard), which fell to 5% post-BCDT.This small observational study in patients with SLE is the first to demonstrate that BCDT results in a significant reduction in levels of IgG aCL.

Background The rat monoclonal antibody 9G4 recognises VH4-34-encoded proteins, enabling the identification of inherently autoreactive B cells. In rheumatoid arthritis (RA), evidence for a humoral immune response encoded by VH4-34 gene has been described in the synovial membrane and within hybridomas derived from rheumatoid synovial tissue. The authors have recently described an expansion of circulating 9G4 + plasmablasts in patients with active RA. Objectives The aim of this study was to determine whether 9G4+ was expressed on autoantibodies commonly associated with RA. Materials and methods Serum from 27 patients with established RA and 46 polyarthritis patients ( Results 23/27 patients with established RA had anti-CCP antibodies, in which eight expressed 9G4. All were positive for both IgM and IgG anti-CCP. Levels of 9G4 expression correlated more closely with IgM than IgG-CCP. In ERA group, 15/23 patients had anti-CCP and 4/23 had 9G4+ anti-CCP. All 4 patients had both IgM and IgG anti-CCP. In ENRA, only one patient had 9G4+ IgM anti-CCP, albeit at low titre. 9G4 was not expressed on TT or PCP antibodies. Conclusions The authors describe the use of the VH4-34 heavy chain gene by autoantibodies to citrullinated peptides early after RA onset. In established RA, usage of VH4-34 by anti-CCP antibodies increased with increasing titre, particularly in IgM-CCP. Therefore, it is possible that the expansion of CCP-specific B cell clones may be due to robust expansion of un-switched B cell clones, possibly including or analogous to those in the splenic marginal zone. This is the first description of the use of the VH4-34 heavy chain gene by autoantibodies to citrullinated peptides. 9G4 expression was largely confined to CCP antibodies from patients with RA.

OBJECTIVE: Small IgG rheumatoid factor immune complexes may provide the trigger for macrophage-derived tumor necrosis factor alpha (TNFalpha) production in rheumatoid arthritis. Immune complexes may bind to any of 3 IgG Fc receptors (FcgammaR). Therefore, the ability of monocyte-derived macrophages to produce TNFalpha was examined following ligation of each of the 3 human FcgammaR, using murine monoclonal antibodies (mAb) to each receptor as a model for small immune complexes. METHODS: Adhered human monocytes expressing all 3 FcgammaR were incubated with murine anti-FcgammaR mAb directed against FcgammaRI, FcgammaRII, or FcgammaRIII. Supernatants were collected at various time points and tested for the presence of TNFalpha and interleukin-1alpha (IL-1alpha) by enzyme-linked immunosorbent assay. RESULTS: The anti-FcgammaRIII mAb induced adhered human monocytes to release TNFalpha. However, F(ab)2 and Fab fragments of the anti-FcgammaRIII mAb failed to induce TNFalpha production. TNFalpha was undetectable following incubation with the anti-FcgammaRI or anti-FcgammaRII mAb. Furthermore, blocking FcgammaRI or FcgammaRII had no effect on the levels of TNFalpha released in response to the anti-FcgammaRIII mAb. Of the 3 anti-FcgammaR mAb, only anti-FcgammaRIII induced IL-1alpha production from adhered human monocytes, and this was inhibited by the presence of a neutralizing anti-TNFalpha mAb. CONCLUSION: This study suggests a dominant role for FcgammaRIIIA in the induction of both TNFalpha and IL-1alpha production by human macrophages in rheumatoid arthritis following receptor ligation by small immune complexes. The signaling of TNFalpha production may require the ligation of either 3 FcgammaRIIIA receptors or only 2 FcgammaRIIIA receptors, where one interaction must involve binding via an Fc domain. In addition, IL-1alpha production following FcgammaRIIIA ligation appears to be dependent on the presence of TNFalpha.

The expression of VH4 gene family during immunoglobulin heavy chain synthesis has been detected in autoimmune diseases. In particular, the rat monoclonal antibody 9G4 detects VH4-34-encoded immunoglobulins and B cells expressing these antibodies as surface receptor (autoreactive 9G4+ B cells).