Interleukin-6 (IL-6) and acute phase proteins in the disease course of patients with systemic lupus erythematosus

Infection in Hospitalized Patients With Systemic Lupus Erythematosus: Proposal of an Algorithm for Diagnosis

BACKGROUND

Identification of infection in patients with systemic lupus erythematosus (SLE) is a major challenge in clinical practice.

OBJECTIVE

This medical records review study evaluated clinical markers, including the performance of C-reactive protein (CRP), neutrophil-lymphocyte ratio (NLR), and platelet-lymphocyte ratio (PLR) in the diagnosis of infection in SLE patients.

METHODS

One hundred four SLE patients hospitalized between 2014 and 2018 were allocated into 3 groups, namely, infection, infection and disease activity, and isolated disease activity. Groups were compared in relation to clinical and laboratory variables. Accuracy measures were calculated for CRP, NLR, and PLR.

RESULTS

C-reactive protein, NLR, and PLR differed between the groups with higher values observed in the infected group, intermediate values in the mixed group, and lower values in the group with isolated activity-CRP (56 vs 26 vs 15 mg/dL, p = 0.002), NLR (7.9 vs 4.0 vs 3.1, p = 0.005), and PLR (270 vs 227 vs 134, p = 0.025). Fever, tachypnea, and PLR were independently associated with infection. The cutoff points of the CRP of 20 mg/L, NLR of 3.5, and PLR of 151.4 presented values of sensitivity and specificity for the prediction of infection equal to 67% and 67%, 65% and 58%, and 71% and 53%, respectively. The developed algorithm showed a sensitivity of 86.6% and specificity of 81% for the diagnosis of infection.

CONCLUSIONS

The combined use of clinical and laboratory markers presented superior accuracy than their isolated use, suggesting a great potential for the application of the algorithm in clinical practice.

A bispecific antibody that targets IL-6 receptor and IL-17A for the potential therapy of patients with autoimmune and inflammatory diseases

Despite the success of current biological therapeutics for rheumatoid arthritis, these therapies, targeting individual cytokines or pathways, produce beneficial responses in only about half of patients. Therefore, better therapeutics are needed. IL-6 and IL-17A are proinflammatory cytokines in many autoimmune and inflammatory diseases, and several therapeutics have been developed to specifically inhibit them. However, targeting both of these cytokines with a bispecific therapeutic agent could account for their nonoverlapping proinflammatory functions and for the fact that IL-6 and IL-17A act in a positive feedback loop. Here, we present the development of MT-6194, a bispecific antibody targeting both IL-6R and IL-17A that was developed with the FynomAb technology. We also present data from mouse inflammatory disease experiments, indicating that simultaneous inhibition of both IL-6 and IL-17A yields enhanced efficacy compared with inhibition of each cytokine alone.

The ratio of erythrocyte sedimentation rate to C-reactive protein is useful in distinguishing infection from flare in systemic lupus erythematosus patients presenting with fever

Background Both C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) can be elevated in systemic lupus erythematosus (SLE) flare and infection, and are therefore of limited utility for distinguishing between the two conditions in febrile SLE patients. Methods A medical records review of hospitalizations (1997-2006) of SLE patients in the Michigan Lupus Cohort was performed. Eligible hospitalizations were those in which patients presented with a temperature of >100.3°F or with subjective fevers as a presenting complaint at admission. Detailed demographic, clinical, and laboratory data were collected. Multivariable logistic regression was used to examine the associations between ESR and CRP and the outcome of flare vs infection, adjusted for confounders. Results Among 557 SLE patients screened, there were 53 eligible hospitalizations (28 flares and 25 infections). Each unit increase in the ratio of ESR:CRP was associated with a 17% increase in the odds of fever being attributable to SLE flare compared to infection (OR 1.17, 95% CI 1.04, 1.31; p = 0.009), when adjusted for white blood cell count, SLE duration, sex, race, and age. ESR and CRP were not individually associated with flare vs infection when modeled with their ratio. Conclusions The ratio of ESR:CRP may provide diagnostic value beyond individual ESR and CRP levels in distinguishing flare vs infection in SLE patients presenting with fever.

Fevers in Adult Lupus Patients

Variability in systemic lupus erythematosus (SLE) disease manifestations is well recognized. Lupus disease activity can range from mild to severe. Fever is a common manifestation of SLE and occurs in 36%-86% of patients. In the Modified Systemic Lupus Erythematosus Disease Activity Index (M-SLEDAI), fever is taken into account as disease activity scoring. Assessment of lupus patients with fever is an important diagnostic challenge, since the initial clinical presentation of a patient with lupus is very similar to the acute febrile phase of an infection. The attribution of fever to SLE holds only after other causes are excluded.

Distinguishing infections vs flares in patients with systemic lupus erythematosus

SLE is a chronic autoimmune disease involving multiple systems. Patients with SLE are highly susceptible to infections due to the combined effects of their immunosuppressive therapy and the abnormalities of the immune system that the disease itself causes, which can increase mortality in these patients. The differentiation of SLE activity and infection in a febrile patient with SLE is extremely difficult. Activity indexes are useful to identify patients with lupus flares but some clinical and biological abnormalities may, however, make it difficult to differentiate flares from infection. Several biological markers are now recognized as potential tools to establish the difference between SLE activity and infection, including CRP and procalcitonin. It is possible, however, that the use of only one biomarker is not sufficient to confirm or discard infection. This means that new scores, which include different biomarkers, might represent a better solution for differentiating these two clinical pictures. This review article describes several markers that are currently used, or have the potential, to differentiate infection from SLE flares.

Association of IFIH1 and pro-inflammatory mediators: Potential new clues in SLE-associated pathogenesis

Antiviral defenses are inappropriately activated in systemic lupus erythematosus (SLE) and association between SLE and the antiviral helicase gene, IFIH1, is well established. We sought to extend the previously reported association of pathogenic soluble mediators and autoantibodies with mouse Mda5 to its human ortholog, IFIH1. To better understand the role this gene plays in human lupus, we assessed association of IFIH1 variants with soluble mediators and autoantibodies in 357 European-American SLE patients, first-degree relatives, and unrelated, unaffected healthy controls. Association between each of 135 genotyped SNPs in IFIH1 and four lupus-associated plasma mediators, IL-6, TNF-α, IFN-β, and IP-10, were investigated via linear regression. No significant associations were found to SNPs orthologous to those identified in exon 13 of the mouse. However, outside of this region there were significant associations between IL-6 and rs76162067 (p = 0.008), as well as IP-10 and rs79711023 (p = 0.003), located in a region of IFIH1 previously shown to directly influence MDA-5 mediated IP-10 and IL-6 secretion. SLE patients and FDRs carrying the minor allele for rs79711023 demonstrated lower levels of IP-10, while only FDRs carrying the minor allele for rs76162067 demonstrated an increased level of IL-6. This would suggest that the change in IP-10 is genotypically driven, while the change in IL-6 may be reflective of SLE transition status. These data suggest that IFIH1 may contribute to SLE pathogenesis via altered inflammatory mechanisms.

Serum free light chains, interferon-alpha, and interleukins in systemic lupus erythematosus

OBJECTIVE

Interleukin-6 (IL-6), interleukin-10 (IL-10), interferon-alpha (IFN-α), and free light chains (FLCs: lambda, kappa) have all been noted to be of importance in systemic lupus erythematosus (SLE). Herein, we quantified and explored the relationship between these inflammatory mediators and disease activity in SLE; and stratified by their current anti-dsDNA antibody status.

METHODS

Seventy-seven SLE patients underwent assessment of disease activity using the SLE disease activity index (SLEDAI). Serum FLC (lambda, kappa, and total), IL-6, IL-10, and IFN-α were quantified. Demographics of disease characteristics were determined by chart reviews. Statistical analyses included Mann-Whitney test, chi square, and linear regression analyses.

RESULTS

Mean (SD) age of the patients was 44.9 ± 12.7 years; SLEDAI (mean ± SD) was 3.4 ± 4.0. Serum lambda FLC levels had a moderate correlation (r = 0.46 with physician global assessment, 0.44 with SLEDAI) and the strongest correlation with disease activity as compared with other inflammatory mediators including current dsDNA antibody status. After adjusting for prednisone use, the correlation of lambda FLC with PGA (r = 0.48) and SLEDAI (r = 0.52) was better than of current dsDNA antibody status with PGA (r = 0.33) and adjusted SLEDAI (r = 0.24), respectively. IL-10 and IFN-α activity did not correlate with disease activity. Serum FLC and IL-6 levels could differentiate between active and inactive SLE patients. Serum lambda FLC and IL-6 levels differed significantly among patients with and without current dsDNA antibodies. Serum lambda FLC levels accounted for 31% of variance in SLEDAI scores.

CONCLUSION

Serum FLC and IL-6 are potentially useful biomarkers of disease activity in SLE. Further studies, with larger study sample and longitudinal design, are indicated.

Cerebrospinal fluid interleukin-6 in central nervous system inflammatory diseases

Background

Interleukin (IL)-6 is recognised as an important cytokine involved in inflammatory diseases of the central nervous system (CNS).

Objective

To perform a large retrospective study designed to test cerebrospinal fluid (CSF) IL-6 levels in the context of neurological diseases, and evaluate its usefulness as a biomarker to help discriminate multiple sclerosis (MS) from other inflammatory neurological diseases (OIND).

Patients and Methods

We analyzed 374 CSF samples for IL-6 using a quantitative enzyme-linked immunosorbent assay. Groups tested were composed of demyelinating diseases of the CNS (DD, n = 117), including relapsing-remitting MS (RRMS, n = 65), primary progressive MS (PPMS, n = 11), clinically isolated syndrome (CIS, n = 11), optic neuritis (ON, n = 30); idiopathic transverse myelitis (ITM, n = 10); other inflammatory neurological diseases (OIND, n = 35); and non-inflammatory neurological diseases (NIND, n = 212). Differences between groups were analysed using Kruskal−Wallis test and Mann−Whitney U-test.

Results

CSF IL-6 levels exceeded the positivity cut-off of 10 pg/ml in 18 (51.4%) of the 35 OIND samples, but in only three (3.9%) of the 76 MS samples collected. CSF IL-6 was negative for all NIND samples tested (0/212). IL-6 cut-off of 10 pg/ml offers 96% sensitivity to exclude MS.

Conclusion

CSF IL-6 may help to differentiate MS from its major differential diagnosis group, OIND.

Tolerogenic function of Blimp-1 in dendritic cells

Blimp-1 has been identified as a key regulator of plasma cell differentiation in B cells and effector/memory function in T cells. We demonstrate that Blimp-1 in dendritic cells (DCs) is required to maintain immune tolerance in female but not male mice. Female mice lacking Blimp-1 expression in DCs (DCBlimp-1(ko)) or haploid for Blimp-1 expression exhibit normal DC development but an altered DC function and develop lupus-like autoantibodies. Although DCs have been implicated in the pathogenesis of lupus, a defect in DC function has not previously been shown to initiate the disease process. Blimp-1(ko) DCs display increased production of IL-6 and preferentially induce differentiation of follicular T helper cells (T(FH) cells) in vitro. In vivo, the expansion of T(FH) cells is associated with an enhanced germinal center (GC) response and the development of autoreactivity. These studies demonstrate a critical role for Blimp-1 in the tolerogenic function of DCs and show that a diminished expression of Blimp-1 in DCs can result in aberrant activation of the adaptive immune system with the development of a lupus-like serology in a gender-specific manner. This study is of particular interest because a polymorphism of Blimp-1 associates with SLE.

High-sensitivity C-reactive protein and erythrocyte sedimentation rate in systemic lupus erythematosus

Levels of C-reactive protein (CRP) have been shown to rise in acute illnesses such as infections and some autoimmune diseases, but not in flares of systemic lupus erythematosus (SLE). Our goal was to investigate the high-sensitivity CRP (hsCRP) response to infection versus disease flare in patients with SLE, and to compare this with the erythrocyte sedimentation rate (ESR) response in these patients. We aimed to determine the hsCRP level that distinguishes between infection and flare in SLE, and investigated the correlation between hsCRP and organ involvement in SLE. We reviewed electronic medical records of all patients with SLE admitted to Cedars Sinai Medical Center between 28 August 2001 and 27 April 2008. Patients were divided into three groups based on the reason for hospitalization: 1) lupus flare; 2) active infection; and 3) both lupus flare and active infection. Data were collected on patient demographics, medication use, microbial culture results, organ involvement in lupus flare, ESR and CRP levels. Data were collected on 85 eligible patients, of whom 54 had a lupus flare, 22 had active infection and eight had both. While the ESR levels did not differ significantly between patients with disease flare and active infection, the hsCRP level was significantly lower in the lupus flare group than in the infection group. Most patients in the lupus flare group who had a significantly high hsCRP level had serositis. We found that at a cut-off of above 5 mg/dl, hsCRP level was correlated with infection with a specificity of 80%. At a cut-off of above 6 mg/dl, hsCRP correlated with infection with a specificity of 84%. hsCRP level was found to be significantly higher in patients with pulmonary involvement than without. hsCRP levels are significantly lower in SLE patients with disease flare than in those with active infection. Elevated hsCRP levels can be used as a predictor of active infection in SLE patients with a high specificity. We review the relationship between IL-6 and hsCRP production in lupus patients.

Selected acute phase proteins and interleukin-6 in systemic lupus erythematosus patients treated with low doses of quinagolide

The relationship between endocrine regulation and immune system has recently become the subject of intense investigations. The objective of this study was to determine the extent of selected serum acute phase proteins (APP), IL-6 and Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) involvement in systemic lupus erythematosus (SLE) patients during quinagolide therapy. A further aim of this study was to evaluate the relationships between the above mentioned parameters. In 25 SLE patients treated with a low dose of quinagolide (12.5-50 microg per day) and in 25 healthy persons who constituted the control group, serum concentration of C-creative protein (CRP), alpha-1-antitripsin (AAT), ceruloplasmin (CER), IL-6 and prolactin (PRL) were estimated at entry and in patients after 3 months of treatment. Moreover, SLEDAI score was calculated at entry and after 3 months of therapy with quinagolide. IL-6 and PRL levels were significantly higher in SLE group whereas the concentrations of CRP, AAT and CER were higher than in the controls, but without statistical significance. After 3 month therapy statistically significant decrease of serum level of IL-6 and PRL was revealed. Statistically significant lower serum concentration of CER was also obtained after 3 months of therapy whereas serum CRP and AAT concentration was lower compared with the mean pretreatment level but the results did not reach statistical significance. A raised SLEDAI score at entry was significantly reduced after 3 month therapy and positive correlation with PRL level in examined group of patients with SLE was noted at entry. The decreased serum concentration of IL-6, APP and SLEDAI score observed during applied therapy with small dose of quinagolide confirms the hypothesis that quinagolide may become a valuable and safe drug in the therapy of patients with mild SLE.

Pathogenic implications for autoantibodies against C-reactive protein and other acute phase proteins

Systemic lupus erythematosus (SLE) is a systemic rheumatic disease characterized clinically by multiorgan involvement and serologically by the occurrence of antinuclear antibodies. SLE patients may present with multiple autoantibodies to cytoplasmic and cell surface antigens as well as to circulating plasma proteins. Another feature of SLE is that serum levels of C-reactive protein (CRP) often remain low despite high disease activity and despite high levels of other acute phase proteins and interleukin-6, i.e. the main CRP inducing cytokine. Apart from its important role as a laboratory marker of inflammation, CRP attracts increasing interest due to its many intriguing biological functions, one of which is a role as an opsonin contributing to the elimination of apoptotic cell debris, e.g. nucleosomes, thereby preventing immunization against autoantigens. Recently, autoantibodies against CRP and other acute phase proteins have been reported in certain rheumatic conditions, including SLE. Although the presence of anti-CRP autoantibodies does not explain the failed CRP response in SLE, antibodies directed against acute phase proteins have several implications of pathogenetic interest. This paper thus highlights the biological and clinical aspects of native and monomeric CRP and anti-CRP, as well as autoantibodies against mannose-binding lectin, serum amyloid A and serum amyloid P component.

Profiles of the acute-phase reactants C-reactive protein and ferritin related to the disease course of patients with systemic lupus erythematosus

OBJECTIVE

To obtain insight in the acute-phase response in SLE.

METHODS

The clinical history, SLEDAI, CRP and ferritin concentrations were analysed throughout the disease course of 10 SLE patients.

RESULTS

During a mean follow-up of 4.8 years, 10 exacerbations (SLEDAI > or = 11) occurred. Throughout the disease course, CRP and SLEDAI correlated positively in 5 patients, whereas the correlation between SLEDAI and ferritin was positive in 7 patients. However, elevated CRP concentrations together with elevated ferritin levels were only observed during 4 exacerbations. Ferritin concentrations were exceptionately high (> 1500 microg/L) during 4 flare-ups. CRP and ferritin levels remained normal during 5 exacerbations.

CONCLUSION

SLE is characterised by highly variable and unusual CRP and ferritin responses that do not always reflect the extent of inflammation in individual patients. Despite severe disease activity, ferritin levels can remain well within the normal range, limiting its clinical usefulness as a marker for disease activity.

Immunopathology and the gene therapy of lupus

Lupus is a chronic autoimmune inflammatory disease with complex clinical manifestations. In humans, lupus, also known as systemic lupus erythematosus (SLE), affects between 40 and 250 individuals, mostly females, in each 100 000 of the population. There are also a number of murine models of lupus widely used in studies of the genetics, immunopathology, and treatment of lupus. Human patients and murine models of lupus manifest a wide range of immunological abnormalities. The most pervasive of these are: (1) the ability to produce pathogenic autoantibodies; (2) lack of T- and B-lymphocyte regulation; and (3) defective clearance of autoantigens and immune complexes. This article briefly reviews immunological abnormalities and disease mechanisms characteristic of lupus autoimmunity and highlight recent studies on the use of gene therapy to target these abnormalities.

IL-6 in autoimmune disease and chronic inflammatory proliferative disease

Interleukin 6 (IL-6), which was originally identified as a B-cell differentiation factor, is now known to be a multifunctional cytokine that regulates the immune response, hematopoiesis, the acute phase response, and inflammation. Deregulation of IL-6 production is implicated in the pathology of several disease processes. The expression of constitutively high levels of IL-6 in transgenic mice results in fatal plasmacytosis, which has been implicated in human multiple myeloma. Increased IL-6 levels are also observed in several diseases, including rheumatoid arthritis (RA), systemic-onset juvenile chronic arthritis (JCA), osteoporosis, and psoriasis. IL-6 is critically involved in experimentally induced autoimmune disease, such as antigen-induced arthritis (AIA), and experimental allergic encephalomyelitis. All these clinical data and animal models suggest that IL-6 plays critical roles in the pathogenesis of autoimmune diseases. Here we review the evidence for the involvement of IL-6 in the pathophysiology of autoimmune diseases and chronic inflammatory proliferative diseases (CIPD) and discuss the possible molecular mechanisms of its involvement.

Corticotropin-releasing factor modulates cardiovascular and pupillary autonomic reflexes in man: is there a link to inflammation-induced autonomic nervous hyperreflexia?

In two recent studies, we found autonomic nervous hyperreflexia in subjects with chronic inflammatory diseases, particularly, in those subjects with higher degrees of systemic inflammation. Since corticotropin-releasing factor (CRF) is induced by inflammatory stimuli and acts within the brain to change neuroendocrine and autonomic activity, we investigated CRF modulation of standard autonomic nervous reflexes. Fifteen healthy subjects were administered 100 microg CRF i.v., which led to a short-term increase of heart rate (p < 0.001) and a decrease in systolic and diastolic blood pressure (p < 0.050). These changes were accompanied by a reduction in heart rate variation at rest (p = 0.010) and during the respiratory sinus arrhythmia test (p = 0.019), and a reduction of pupillary latency time (p = 0.038). In further 21 normal subjects we studied the effect of prednisolone treatment on autonomic nervous function (100 mg/d during three days --> CRF reduction), which resulted in an increase of heart rate (p < 0.001), increase of heart rate variation during the respiratory sinus arrhythmia test (p < 0.001), increase in pupillary latency time (p = 0.012), a increase in maximal pupillary area (p = 0.002), and a decrease in diastolic blood pressure (p = 0.002). In conclusion, induction of a low central CRF content by prednisolone leads to a marked hyperreflexia in respiratory sinus arrhythmia and hyporeflexia in the latency time test. It is obvious that CRF can regulate autonomic reflexes. Possibly, central CRF status may also influence autonomic reflexes during chronic inflammation due to chronically changed central CRF concentration.

IL-6-like cytokines and cancer cachexia: consequences of chronic inflammation

An estimated 30% of cancer deaths are attributed to cachexia and its consequences. Cachexia (wasting syndrome) is the hypercatabolism of the body's carbon sources, proteins and lipids, for conversion into energy. It is induced by a variety of pathological conditions, including cancer. Among the inflammatory responses to cancer is the synthesis of cytokines, including IL-6 and related cytokines. These cytokines have been found to induce cachexia by altering metabolism of lipids and proteins. IL-6-like cytokines have been found to inhibit lipid biosynthesis by adipocytes, which increased the rate of lipid catabolism. Others have described the atrophy and increased catabolism of muscle protein due to IL-6. A cytokine closely-related to IL-6 is leptin, which plays a major role in lipid metabolism under normal conditions. The role of leptin in pathological conditions such as cancer cachexia has not yet been fully elucidated. Detailed mechanistic information about the induction of cancer cachexia by IL-6-like cytokines requires more research.

Interleukin-10 and interleukin-6 in lupus erythematosus and rheumatoid arthritis, correlations with acute phase proteins

We sought to investigate the influence of interleukin-10 (IL-10) and IL-6 on the acute phase proteins (APP) in systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). IL-10, IL-6, Creactive protein (CRP), alpha-1-acid glycoprotein (AGP), and alpha1 antichymotrypsin (ACT) serum levels were determined in one hundred-eight patients (71 with SLE, 37 with RA). Quantification of the serum IL-10 level showed increased levels in SLE and RA patients as compared to healthy controls. Serum IL-6 level was found to be elevated in SLE and RA patients. A correlation between IL-10 and IL-6 serum level was found only in SLE. CRP and AGP serum levels were increased in RA as compared to controls, whereas in SLE only AGP was found elevated. A statistically significant correlation between IL-6 serum level and CRP, AGP and ACT was found only in RA. No correlation between IL-10 and serum level of CRP, AGP and ACT was established. Since IL-10 has a potent immunosuppressive activity, we expected it to be negatively correlated with APP levels. Surprisingly, IL-10 did not correlate with APP either in SLE or RA patients. However, the elevation of IL-10 serum levels in SLE and RA and the correlation between IL-10 and IL-6 in SLE may suggest that IL-10 may play a central role in inflammatory connective tissue diseases.

Serum and urinary interleukin-6 in systemic lupus erythematosus

Dysregulation of IL-6 production has been proposed as a pathogenic mechanism in SLE. We asked if serum or urine IL-6 levels could serve as indicators of systemic lupus erythematosus (SLE) disease activity. Using a sensitive enzyme-linked immunosorbent assay (ELISA), we measured serum and urine IL-6 in 56 SLE patients. Disease activity was assessed using a standard clinical index, the Systemic Lupus Activity Measure (SLAM). Only seven of 56 SLE patients had elevated serum IL-6 levels, compared with 1 of 32 controls (NS). SLE disease activity did not correlate with serum IL-6 levels. Sixteen of 50 SLE patients in whom urine IL-6 was measured exhibited elevated urine IL-6 levels, compared with 1 of 17 controls (p = < 0.05). Urine IL-6 levels correlated with overall disease activity and with the presence of active urinary sediment. Our results indicate that serum IL-6 is not a predictor of disease activity in SLE, but that urine IL-6 may be a marker of active nephritis.

Cytokine production (IL-6 and TNF alpha) in whole blood cell cultures of patients with systemic lupus erythematosus

Whole blood cell culture has great advantage over isolated peripheral blood mononuclear cell culture, because it needs only small amounts of blood and is fast to perform. The current report focuses on the measurement of IL-6 and TNF alpha produced by peripheral blood monocytes of patients with systemic lupus erythematosus (SLE) in the whole blood cell culture system. After an initial triggering with lipopolysaccharide (LPS), a specific stimulus for monocytes, a decreased production of IL-6 relative to the controls was observed. Dividing our SLE patients according to treatment with corticosteroids, overall the IL-6 production was decreased in the patients treated with corticosteroids. TNF alpha production was comparable with normals, with the exception of an increased spontaneous production and using LPS stimulus of 4 pg/ml. In the patients treated with corticosteroids a decreased TNF production was observed, in contrast to the non-treated patients in which an increased TNF production was found compared with the controls using LPS doses higher than 62 pg/ml. The impaired acute phase reaction (APR) that has been described in the literature, might be explained by our observation of a decreased production of mainly IL-6. However, also this study showed that treatment has a strong impact on ex vivo IL-6 and TNF production.

Serological markers of disease activity in systemic lupus erythematosus

When measured serially by Farr assay at a frequency of approximately once a month, changes in levels of anti-dsDNA appear to be a good predictor of clinical disease activity. Although the role of antibodies to the RNA component of snRNP awaits further studies, measurement of anti-UsnRNP antibody levels seems to be of limited value in monitoring lupus patients in clinical practice. The same holds for antibodies to SSA (Ro) and anti-histone antibodies. More recently described antibodies to C1q are probably useful in the follow-up of SLE patients suspected of proliferative renal involvement. The best alternative to measuring levels of the antibodies mentioned before is probably serial analysis of activation of the complement cascade. Levels of complement factors like C3, C4 and, functionally, CH50 remain a useful parameter for monitoring disease activity in SLE, although fluctuations in anti-dsDNA as measured by Farr assay seem superior with respect to sensitivity and specificity for an ensuing relapse. Despite the problems in sampling, measuring levels of activated split products of complement factors like C3a, C3d or C5a may prove to be a valuable tool in the follow-up of lupus patients. The involvement of the endothelial surface is illustrated by rising sVCAM-1 levels prior to relapses in SLE. Although one could expect that subsequent inflammation should be reflected by increased levels of inflammatory molecules like CRP and IL-6, the use of these molecules as predictors of lupus activity seems limited. Interferon-alpha as a direct reflector of the effector phase seems, however, rather promising in this respect and awaits longitudinal studies to analyse the possible relation with clinical disease activity and other serological parameters.

Cytokine gene profile in circulating blood mononuclear cells from patients with systemic lupus erythematosus: increased interleukin-2 but not interleukin-4 mRNA

Cytokines are important in developmental and effector pathways of lymphocyte function. Our objective was to elucidate the profile of cytokines produced by circulating mononuclear cells from patients with systemic lupus erythematosus as estimated from studies of cytokine-gene activation. cDNA prepared by reverse transcription of lymphocyte mRNA was amplified using the polymerase chain reaction and normalized on the basis of beta-actin gene expression. Of 10 cytokines investigated in 16 individuals, differences between SLE and controls were found in only three. IL-2 transcripts were detected in four of six cases of subjects hospitalized for active SLE, but in only one of seven healthy controls, and none of three cases with pulmonary tuberculosis. By contrast, IL-4 transcripts were decreased compared with healthy controls and patients with tuberculosis. Also, TGF beta transcripts appeared to be decreased in SLE. All individuals studied regularly demonstrated high levels of transcripts for IL-1 beta, IL-6 and TNF alpha and transcripts for IFN gamma, TNF beta, IL-5 and IL-10 were variably expressed. In a second group of six SLE patients with less active disease, there was also a decrease in IL-4 expression compared with six healthy controls. Moreover, assays performed on sera from patients with active SLE revealed that IL-4 levels were not increased. Although in mice this cytokine has a well documented role in supporting antibody production, this study provides no evidence that IL-4 is involved in the B cell hyperactivity characteristic of human SLE.

Interleukin 6 promotes murine lupus in NZB/NZW F1 mice

To investigate the role of IL-6 in systemic lupus erythematosus (SLE), we selectively inhibited IL-6 in lupus-prone NZB/NZW F1(B/W) mice by chronic administration of a rat mAb to mouse IL-6. Anti-IL-6 alone elicited an anti-rat response that blocked its biologic effects. To circumvent this problem, we rendered B/W mice tolerant to the rat mAb by administration of anti-CD4 concurrent with the first dose of anti-IL-6. Thereafter, the mice received weekly injections of anti-IL-6 alone. There were two control groups: one group received the tolerizing regimen of anti-CD4 along with a control rat IgG1 mAb (GL113) instead of anti-IL-6; the other control group received PBS. Mice that received anti-CD4 were tolerant to the rat mAb for 6 mo. Throughout this period, treatment with anti-IL-6 prevented production of anti-dsDNA, significantly reduced proteinuria, and prolonged life. Mice that received anti-IL-6 without anti-CD4 developed an immune response to the rat mAb and then developed anti-dsDNA antibodies, proteinuria, and mortality comparable with control mice. These findings establish that IL-6 promotes autoimmunity in B/W mice. They further indicate that, although mAb to IL-6 can suppress murine lupus, the development of host immunity to the mAb abrogates its beneficial effects. Finally, this is the first study to demonstrate that a brief course of anti-CD4 can induce tolerance to another therapeutic mAb, in this case an anti-cytokine mAb.

Immune function of patients receiving recombinant human interleukin-6 (IL-6) in a phase I clinical study: induction of C-reactive protein and IgE and inhibition of natural killer and lymphokine-activated killer cell activity

Interleukin-6 (IL-6) is a cytokine that acts on a variety of cell types, including myeloid progenitor cells and B and T lymphocytes. It has been found to activate cytotoxic T cells and natural killer (NK) cells and to induce T-cell-mediated antitumour effects in animal models. In a phase I clinical trial of recombinant human IL-6, 20 patients with advanced cancer were entered to receive daily subcutaneous injections of IL-6 over 7 days followed by a 2-week observation period and another 4 weeks of daily IL-6 injections. Doses varied between 0.5 microgram/kg and 20 micrograms/kg body weight and immune functions were monitored throughout. At all dose levels IL-6 administration led to a marked increase in serum levels of C-reactive protein and a moderate rise in complement factor C3. The proportions of CD4, CD8 or HLA-DR lymphocytes in peripheral blood did not alter with IL-6 treatment nor did the in vitro proliferation of peripheral blood mononuclear cells induced by either phytohaemagglutinin, pokeweed mitogen or fixed Staphylococcus aureus. By contrast, NK cell activity, lymphokine-activated killer (LAK) cell activity and proliferation induced by in vitro culture with interleukin-2 (IL-2) were suppressed at doses exceeding 2.5 micrograms/kg. Serum IgE levels were consistently elevated over the IL-6 dose range but IgM, IgG and IgA levels were unaffected. In summary there is a dose-dependent induction of acute-phase proteins by in vivo IL-6 treatment. At higher IL-6 doses there is a suppressive effect on NK and LAK activity measured in vitro. IL-6 may thus be useful in combination cytokine therapies that seek to suppress LAK and favour cytotoxic T lymphocyte responses. The rise in IgE levels in response to IL-6 was unexpected and suggests a more pivotal role than previously known for the control of IgE production; this could include IgE-related diseases.

Profiles of cytokines (TNF alpha and IL-6) and acute phase proteins (CRP and alpha 1AG) related to the disease course in patients with systemic lupus erythematosus

Tumor necrosis factor alpha (TNF alpha) and interleukin-6 (IL-6) play a main role in inducing acute phase protein production by hepatocytes. This study describes the serum levels of TNF alpha and IL-6 in relation to serum levels of C-reactive protein (CRP) and alpha 1-acid glycoprotein (alpha 1AG) in three systemic lupus erythematosus (SLE) patients. Disease courses of these patients were divided in a total of 19 clinical periods, according to the clinical symptoms and interleukin profiles. Significantly elevated TNF alpha levels were found in all but three of the defined periods, without being associated with disease activity. In only four of the defined periods elevated TNF alpha were observed combined with elevated IL-6 and CRP levels. Two of these periods coincided with minor symptoms of SLE, one with an exacerbation and the other one with a systemic infection while SLE activity was low. All other periods showed varying combinations of elevated TNF alpha and/or IL-6 levels being followed or not by elevated CRP levels. Significantly raised alpha 1AG levels were measured in all clinical periods. In most of the observed periods a dissociation was found between TNF alpha and IL-6 and also between the different cytokine (TNF alpha and IL-6) levels and acute phase protein (CRP and alpha 1AG) levels. These data could not be explained by differences in disease course or influences of medication. We conclude that more factors other than TNF alpha and IL-6 must play a role in the regulatory pathway of the acute phase response in SLE.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of recombinant tumour necrosis factor (rTNF-alpha) in cancer. Observations on the acute phase protein reaction and immunoglobulin synthesis after high dose recombinant TNF-alpha administration in isolated limb perfusions in cancer patients

To obtain insight in the effect of TNF on the synthesis of acute phase proteins like CRP, alpha 1-antitrypsine, alpha 1-acidglycoprotein, C3 and C4 and the immunoglobulins (IgG-M-A), nine cancer patients who were treated with an isolated limb perfusion (ILP) with high dose recombinant TNF-alpha (rTNF-alpha) were investigated during a 7-day period after the end of the perfusion. Resorption of rTNF-alpha from out of these limbs into the circulation after the ILP induced within 30 min to 6 h in all patients elevated serum levels of IL-6. At the same time C-reactive protein became detectable in serum. The highest serum levels were obtained at 48 h after ILP. The serum levels of the other acute phase proteins (alpha 1-acidglycoprotein, alpha 1-antirypsine, C3, C4), rose more slowly and the highest serum levels were found at the third day. All investigated proteins declined after they had reached their peak levels. Levels of alpha 1-acidglycoprotein and alpha 1-anti-trypsin alpha 1-acid declined slower than both complement component. In regard to the immunoglobulin levels a nearly continuous increase in the serum level of specifically IgM was observed. This study clearly shows the interrelationship between TNF-alpha and IL-6 in regard to the synthesis of the different acute phase proteins; and moreover also a striking effect on IgM synthesis.

Immunoreactive interleukin-6 in serum of patients with B-lymphoproliferative diseases

Serum immunoreactive interleukin-6 (ir-IL-6) concentration was measured by radioimmunoassay in nine patients with chronic lymphocytic leukaemia (CLL), 16 patients with multiple myeloma (MM), 12 patients with monoclonal gammapathy of undetermined significance (MGUS), 22 patients with primary Sjögren's syndrome (SS), and in 32 control subjects. Measurable quantities of ir-IL-6 were detected in every sample studied. Patients with MGUS and SS had significantly higher serum ir-IL-6 (mean +/- SD) concentrations (337 +/- 92 ng l-1 and 299 +/- 100 ng l-1, respectively) than controls (92 +/- 77 ng l-1) and patients with CLL and MM (120 +/- 32 ng l-1 and 113 +/- 58 ng l-1, respectively). Longitudinal studies of ir-IL-6 concentration in a few patients with MM showed a decrease before remission and an increase prior to relapse, but no consistent pattern was detected. In conclusion, we found that serum ir-IL-6 levels are higher in patients with benign hypergammaglobulinaemic states than in patients with malignant neoplastic B-cell disorders.

Plasma concentration of IL-6 in systemic lupus erythematosus; an indicator of disease activity?

To investigate the possible role of IL-6 in the activation of the autoimmune process in systemic lupus erythematosus (SLE), we serially measured concentrations of IL-6, IgG, and anti-dsDNA antibodies before and during exacerbations in patients with SLE. In addition, we serially related the IL-6 response to the generation of the acute phase reactant C-reactive protein (CRP). Sixteen consecutive patients who developed an exacerbation were analysed in this study. Blood samples were drawn in EDTA monthly. At the time of maximal disease activity during exacerbation, IL-6 plasma concentrations were increased (greater than or equal to 6 pg/ml) in 12 out of the 16 cases. Concentrations of IL-6 correlated with the concentrations of CRP (P less than 0.01) and the score of the disease activity index (P less than 0.05). No correlation was found between IL-6 concentrations and concentrations of anti-dsDNA or IgG. The course of changes in IL-6 concentrations before the exacerbation was variable. Five out of the 16 exacerbations studied were characterized by a prominent rise of IL-6 at the time of maximum disease activity. In this subgroup serositis as well as elevated concentrations of CRP were observed more frequently (P less than 0.02). Seven exacerbations were not accompanied or preceded by changes in IL-6 concentrations and showed generally low IL-6 concentrations. In this latter subgroup cerebral involvement was seen more frequently (P less than 0.02). Our data do not suggest a pathogenic role for IL-6 in the generation of IgG and/or anti-dsDNA antibodies before exacerbations. Rises of IL-6 concentrations before exacerbations in SLE seem only to occur in a subgroup of patients with SLE characterized by the presence of serositis and elevated concentrations of CRP during exacerbation.

Plasma interleukin-6 and renin substrate in reactive arthritis, rheumatoid arthritis, and systemic lupus erythematosus

In order to study the role of interleukin-6 (IL-6) in inflammatory disease we monitored plasma levels of IL-6 and acute phase proteins such as C-reactive protein (CRP) and renin substrate (RS) in patients with reactive arthritis (ReA), rheumatoid arthritis (RA), and systemic lupus erythematosus (SLE). Venous plasma samples were collected: (1) during the acute phase or exacerbation of the disease, and (2) several months latter during convalescence. Increased mean [95% confidence intervals (CI)] levels of plasma IL-6 were observed in patients with ReA both in the acute phase and later, 229 (177 to 280) ng/l and 197 (134 to 260) ng/l respectively (P less than 0.001 as compared to controls). The corresponding plasma IL-6 levels in RA patients were 283 (223 to 340) ng/l and 183 (151 to 226) ng/l, respectively (P less than 0.001 as compared to controls). Plasma IL-6 levels in SLE patients were not increased. Plasma RS levels were increased in all patient groups, but no significant correlation to IL-6 or CRP levels was observed, whereas plasma IL-6 and CRP levels showed a positive correlation in ReA and RA patients.

Observations on the interleukin-6 and acute phase protein profiles in the disease course of patients with lupus erythematosus

In vitro models have shown that interleukin-6 (IL-6) is the main dominator of the stimulation of the full spectrum of acute phase proteins. This study describes IL-6 levels in relation to levels of acute phase proteins in 15 systemic lupus erythematosus (SLE) patients, with special attention given to those patients with increased serum levels of IL-6. Three episodes with elevated levels of IL-6 were observed in a period shortly after a flare-up of SLE, in three of the 15 patients. In one of these three patients a clear increase in the C-reactive protein (CRP) level, preceded by an IL-6 increase, was observed. In the other two patients, CRP levels remained unchanged. It is speculated that, next to IL-6, another signal is operative or needed for the start of an acute phase reaction. However, influences of the disease itself or of the administered therapy cannot be excluded as the cause of the described discrepancy between IL-6 and acute phase protein profiles in these two SLE patients.

Hypogalactosylation of immunoglobulin G sugar chains and elevated serum interleukin 6 in Castleman's disease

Immunoglobulin G (IgG) molecule has two N-linked complex type oligosaccharides, consisting of a mixture of at least 12 different structures. The pattern of these oligosaccharides is fairly constant in healthy individuals. In three patients with Castleman's disease, in whom serum interleukin 6 (IL-6) levels were elevated, agalactosyl species of serum IgG oligosaccharides were markedly increased as compared to those of normal healthy controls. A close relationship between increased IL-6 and altered IgG oligosaccharide structure is suggested.

Anaemia of chronic disease in rheumatoid arthritis. Raised serum interleukin-6 (IL-6) levels and effects of IL-6 and anti-IL-6 on in vitro erythropoiesis

Serum and bone marrow from 21 patients with rheumatoid arthritis (RA) were studied in order to establish the pathogenetic role of interleukin-6 (IL-6) in anemia of chronic disease (ACD). Erythroid colony growth, using burst forming units of erythroblasts (BFUe) as a parameter, was impaired in ACD and not in nonanemic RA controls. Serum IL-6 was elevated in ACD and it correlated well with parameters of disease activity such as erythrocyte sedimentation rate and C-reactive protein. IL-6 addition to bone marrow cultures had inconsistent effects while anti-IL-6 addition resulted in impaired erythroid colony growth, suggesting stimulatory effects of IL-6 produced in the medium, which may be masked by simultaneous production of cytokines with suppressive effects. It was concluded that elevated serum IL-6 in ACD reflects disease activity. It probably plays no pathogenetic role in ACD. Its stimulatory effects on erythroid growth might counteract suppressive effects of other interleukins.

Interleukin 6 production in the central nervous system during experimental autoimmune encephalomyelitis

Interleukin 6 (IL6) is one of the major inflammation-associated cytokines. Elevated serum or tissue levels of IL6 have been reported to occur in several human diseases, including infections of the central nervous system (CNS), but not in non-infectious CNS inflammation, e.g. multiple sclerosis. While studying experimental autoimmune encephalomyelitis (EAE) as an animal model for autoimmune inflammation of the CNS, we found increased IL6 levels in the CNS of mice suffering from a lethal form of the disease. IL6 levels in the spleens and sera were not significantly increased. These findings are indicative of local production of IL6 in the CNS during EAE, and represent the first demonstration of IL6 production in non-infectious CNS inflammatory disease.