Association of complement factor B allotypes and serum biomarkers in rheumatoid arthritis patients and their relatives

The aim of the study was to investigate the allotypic variability of complement factor B (BF) in patients and relatives with rheumatoid arthritis (RA) and its association with serological biomarkers and clinical features of the disease. BF allotypes were determined by high‐voltage agarose gel electrophoresis in serum samples of 180 patients with RA, 198 relatives and 98 controls from Southern Brazil. Anticyclic citrullinated peptide (anti‐CCP), antimutated citrullinated vimentin (anti‐MCV) and IgA‐rheumatoid factor (RF) were determined by ELISA and IgM‐RF by latex agglutination in all samples. No significant differences were found in the allotypic variants of BF between patients with RA, relatives and controls, nor associations with gender and age of RA onset. BF*S07 allotype was significantly associated with extra‐articular manifestations (EAMs; Secondary Sjögren Syndrome, pneumonitis, rheumatoid nodules) in patients with RA (P = 0.02; OR = 6.62). Patients with phenotype BF F had lower positivity for anti‐MCV biomarker (P = 0.02; OR = 0.22) and those with allotype BF*S had higher prevalence of this autoantibody (P = 0.02; OR = 3.77). An increased frequency of RF‐IgA was detected in relatives of patients with RA with BF FS07 phenotype (P = 0.02; OR = 7.78). Complement BF variability did not influence the development of RA in the studied patients, but BF variants may act as markers of disease prognosis, such as development of EAMs, corroborating with the role of the alternative pathway in the pathogenesis of RA.     

Metabolism of factor B of serum complement in rheumatoid arthritis.

An increased rate of catabolism of radio-iodinated Factor B has been shown in five out of ten patients with rheumatoid arthritis. Serum levels of Factor B were normal, the increased catabolism being matched by increased synthesis. The patients showing high catabolic rates had more manifestations of extra articular disease than did those with normal catabolic rates and they had higher rheumatoid factor titres. In seven patients, the catabolic rate for Factor B correlated significantly with the rate of IgG catabolism. In this series, the Raji-cell assay for immune complex-like material was in the normal or near normal range in all but one patient.     

C4 complement allotypes in juvenile dermatomyositis

Twenty probands with juvenile dermatomyositis and their relatives were studied to determine the inherited segregation patterns of class I, II, and III HLA region markers including C4A, C4B, Bf, and C2 complement polymorphisms. The extended haplotype B8, DR3, C4A*Q0, C4B*1, C2*C, and Bf*S was present in 13 of the 20 probands. Three other probands also carried a haplotype with a null allele for C4A and two further probands carried a null allele for C4B; only two probands had no detectable C4 null allele. These data confirm previous studies showing high frequencies of B8 and DR3 in patients with juvenile dermatomyositis, but show that there is a higher association with null alleles of C4. This suggests that the C4 genes are either themselves the disease-susceptibility genes or are in very strong linkage disequilibrium with such genes.     

Immune complex detection and complement activity in rheumatoid arthritis: a comparative study of a radioimmunoassay using monoclonal rheumatoid factor, gel diffusion techniques and C4 activity.

Paired sera and synovial fluids from forty-nine patients with rheumatoid arthritis and twenty-five with other forms of arthritis were tested for immune complexes by a radioimmunoassay using monoclonal rheumatoid factor and gel diffusion procedures with monoclonal rheumatoid factor and C1q. Synovial fluid hemolytic C4 and C4 adjusted for IgG concentration were determined in both groups of patients. Immune complexes were detected at similar high frequencies in the rheumatoid synovial fluids by precipitin formation with monoclonal rheumatoid factor (68%) and C1q (71%). In contrast, immune complexes in rheumatoid sera were detected in low frequency by precipitin reactions with monoclonal rheumatoid factor (10%) and C1q (0%). Using the monoclonal rheumatoid factor radioimmunoassay, thirty-one (63%) synovial fluids exceeded the mean non-RA binding activity by one standard deviation. Similarly, twenty-four (49%) rheumatoid sera exceeded the mean non-RA binding activity to one standard deviation. Synovial fluid C4 adjusted for IgG as well as IgG alone distinguished between the two groups of patients whereas the C4 values did not. The C4/IgG value showed a strong negative correlation with the monoclonal rheumatoid factor radioimmunoassay and C1q precipitin formation.     

Association of rheumatoid factor with complement activation in rheumatoid arthritis and other diseases.

Rheumatoid factor (RF) is a complement activating autoantibody. In rheumatoid arthritis (RA) the rate of catabolism of complement is closely related to the titre of RF. Therefore, we have examined whether these relationships are unique to RA or will be found in non-RA disorders in which RF may be found in the circulation. We studied patients with subacute bacterial endocarditis, leprosy, tuberculosis, and a variety of other rheumatic and vasculitic disorders. We found that in all the disorders examined the RF had a complement activating potential which was equivalent to that of the RF of RA patients. Furthermore in vivo activation of complement, as exhibited by the appearance of C3 degradation products, was significantly related to higher titres of haemolytically active RF in non-RA as well as the RA group. In these respects, therefore, the RF in RA and non-RA patients is indistinguishable. A possible survival value for RF is discussed.     

Life stress and rheumatoid arthritis. A 15-year follow-up study

A 15-year follow-up study of 74 female patients with definite or classic rheumatoid arthritis (RA) was performed with special focus on the association between life stress and clinical course of the illness. Two categories of RA could be classified: a disease form less connected with genetic factors and more influenced by major psychodynamic conflict situations ('major conflict group' MCG) and a second form more associated with hereditary predisposition and less influenced by environmental psychosocial changes ('non-conflict group', NCG).     

Measurement of terminal complement complexes in rheumatoid arthritis.

Though complement activation is recognized as a central event in inflammation in the rheumatoid joint, little attention has been paid to the role of the cytolytic membrane attack complex of complement in the pathogenesis of this disease. The membrane attack complex causes a variety of non-lethal effects in nucleated cells, including stimulation of release of inflammatory mediators, and cell proliferation. Thus in the rheumatoid synovium, non-lethal effects of complement membrane attack may play a major role in disease pathology. In order to investigate this possibility, assays for the detection of terminal complement complexes in biological fluids have been established, and used to demonstrate membrane attack pathway activation in rheumatoid arthritis. Terminal complement complexes were present in increased levels in synovial fluid (mean, 1,334 ng/ml) and plasma (mean, 513 ng/ml) in 20 patients with rheumatoid arthritis when compared with controls (mean, 285 ng/ml and 129 ng/ml respectively). Using an assay specific for the SC5b-9 complex it was demonstrated that the raised levels of terminal complement complexes in rheumatoid synovial fluid consisted of a mixture of inactive SC5b-9 complexes and fluid-phase complement membrane attack complexes.     

Restriction fragment length polymorphism of complement C4 in Japanese patients with rheumatoid arthritis and normal Japanes

Restriction fragment length polymorphism (RFLP) of the two genes for complement C4A and C4B was studied in 56 Japanese patients with rheumatoid arthritis (RA) and 161 normal individuals. HindIII digestion revealed six common patterns, from which the segregation of three common RFLP-types were deduced; 32-15 kb, 32-25 kb, and 32-20-13-6.5 kb. The last type showed positive associations with C4B5 and HLA-DR4. In the RA patients, an increase of this type was found as well as a decrease of the 32-15 kb/32-25-15 kb heterozygotes.     

A study of complement fixation by rheumatoid factor using a haemolytic assay system.

Complement fixation by rheumatoid factor (RF) in sera from rheumatoid arthritis patients has been investigated by means of a haemolytic assay system employing sheep erythrocytes (SRBC) coated with reduced and alkylated rabbit IgG anti-SRBC antibody. Haemolysis was almost invariably detected with RF-positive sera whereas haemolysis was not observed with RF-negative sera; It was evident from a marked increase in haemolysis, obtained following isolation of IgM-RF of high purity from several RF-positive sera, that the full in vitro complement-fixing ability and hence lytic potential of RF in serum is masked. Parallel observations were also made with synovial fluids. The inhibition of haemolysis by RF in sera and synovial fluids commonly involved a reduction in degree of lysis at high concentration of test material as well as a more generalized inhibition in overall percentage lysis. Complete replication of typical RF-positive serum and synovial fluid patterns of lysis on dilution was achieved by addition of heat-aggregated human IgG to isolated IgM-RF preparations and demonstrated that the two inhibitory effects are separable in terms of complement depletion and reduction of free rheumatoid factor antibody activity, respectively.     

Terminal complement complexes and C1/C1 inhibitor complexes in rheumatoid arthritis and other arthritic conditions.

Terminal complement complex (TCC) and C1r-C1s-C1 inhibitor complex (C1/C1 INH) concentrations were measured in plasma and synovial fluid from patients with arthritis and related to other measures of disease activity. Both TCC and C1/C1 INH concentrations were significantly increased in patients with rheumatoid arthritis (RA) compared with patients with osteoarthritis (plasma and synovial fluid, P less than 0.05) and normal subjects (plasma only, P less than 0.001). In the patients with RA, there was no correlation between plasma or synovial fluid TCC concentrations and IgM rheumatoid factor, immune complex or C1/C1 INH levels. However, in 10 patients with seronegative RA, C1/C1 INH and immune complex levels correlated significantly in synovial fluid (r = 0.69, P less than 0.05) although not in plasma (r = 0.52). Plasma and synovial fluid TCC and C1/C1 INH concentrations did not differ in rheumatoid patients with severe compared with mild joint disease (categorized by the Ritchie score). These results confirm a role for complement activation in RA but suggest that several mechanisms are involved in its pathogenesis.     

Immunoglobulins and complement factor C4 in adult rhinosinusitis

We assessed whether complement and its factor C4 or abnormal immunoglobulin levels are associated with chronic or recurrent rhinosinusitis. We used multiple patient and control groups to obtain clinically meaningful data. Adult chronic or recurrent rhinosinusitis and acute purulent rhinosinusitis patients were compared with unselected adults and controls without previous rhinosinusitis. Associated clinical factors were reviewed. Levels of immunoglobulins, plasma C3, C4 and classical pathway haemolytic activity were analysed. C4 immunophenotyping was used to detect C4A and C4B deficiencies as null alleles. Complement was up-regulated in rhinosinusitis. C4A nulls and low IgA, IgG, IgG1, IgG2, IgG3 and IgG4 levels were all more common in chronic or recurrent rhinosinusitis patients than in unselected and healthy controls. We searched for relevant differences between the patient groups. According to stepwise logistic regression analysis, nasal polyposis [odds ratio (OR) 10.64, 95% confidence interval (CI) 2.5-45.7, P = 0.001], bronchial asthma (OR 8.87, 95% CI 2.3-34.9, P = 0.002), C4A null alleles (OR 5.84, 95% CI 1.4-24.9, P = 0.017) and low levels of IgG4 together with either IgG1 or IgG2 (OR 15.25, 95% CI 1.4-166.8, P = 0.026) were more common in chronic or recurrent rhinosinusitis than in acute rhinosinusitis patients. Isolated low IgG subclasses had limited value in patient assessment. C4A null alleles are associated with chronic or recurrent rhinosinusitis, potentially through their effect on immune defence and inflammation control. Multiple clinical and immunological parameters may need to be evaluated when searching for prognostic variables.     

Role of leukotriene B4 receptors in rheumatoid arthritis

The purpose of this review is to summarize the role that murine models of arthritis are playing in the understanding of human rheumatoid arthritis and how leukotriene B(4) (LTB(4)) is emerging as an important target in this field. Both the collagen-induced arthritis (CIA) model and the K/BxN serum transfer arthritis model have contributed to outline the potential mechanisms involved in inflammatory arthritis. Indeed, the CIA model has contributed to the development of effective anti-TNFalpha and anti-IL-1beta based treatments for RA that are currently in the clinic. Many recent studies in mouse models have suggested a critical role for LTB(4) and its receptors in the development of inflammatory arthritis. Inhibitors of LTB(4) biosynthesis as well as LTB(4) receptors are protective in mouse models of RA and mice deficient in the LTB(4) biosynthetic enzymes or LTB(4) receptors are resistant to disease development suggesting several promising targets for RA in this pathway.     

Circulating immune complexes and complement in rheumatoid arthritis

Rheumatoid arthritis is characterized immunologically by the detection of rheumatoid factor (RF) and circulating immune complexes (CIC). The pathogenesis role played by these CIC has been discussed a long time. A part of this theoretical question, it could be of interest to know if these technics could help the clinician in the diagnosis or in the follow up of the patients with RA.     

Unequal expression of complement C4A and C4B genes in rheumatoid synovial cells, human monocytoid and hepatoma-derived cell lines

C4A and C4B are closely related homologous complement proteins encoded in the class III region of major histocompatibility complex (MHC). The regulation of their expression is under genetic and hormonal control. In this study we investigated the synovial fluid plasma ratio of C4A and C4B of rheumatoid (RA) and osteoarthritis (OA) patients, and a predominance of the C4B gene expression by the synovial macrophages of RA patients was demonstrated. To clarify the tissue specificity of the expression of C4A and C4B genes, human monocytoid cell line U937 and hepatoma-derived HepG2 cells were studied. The gene expression of C4A and C4B were markedly different in these cells since a relative predominance of C4B mRNA in U937 cells and excess of that of C4A in HepG2 cells were detected. Recombinant interferon-gamma (IFN-gamma) up-regulated the expression of C4A gene in both cells, but had apparently no effect on the C4B gene. Our results demonstrate dissimilar expression patterns for the two human C4 genes, suggesting different tissue specific regulation of human C4A and C4B.     

Conjugal prevalence of rheumatoid arthritis, rheumatoid factor and other autoantibodies in rheumatoid arthritis

The prevalence of rheumatoid arthritis, rheumatoid factor, antinuclear autoantibodies, thyroglobulin and thyroid `microsomal'' autoantibodies and gastric parietal cell autoantibodies has been studied in 327 husbands and 181 wives of 508 probands with seropositive `definite'' or `classical'' rheumatoid arthritis as defined by the American Rheumatism Association diagnostic criteria. Two husbands and three wives had definite rheumatoid arthritis: this prevalence is no higher than one might expect. A higher prevalence of all five autoantibodies was found in husbands compared with age matched controls, but only in respect of antinuclear autoantibodies and thyroglobulin autoantibody were the differences statistically significant. In the wives only rheumatoid factor showed a significantly higher prevalence as compared with controls. The presence of autoantibodies in husbands and wives showed no relationship to the duration of marital contact nor to the presence of the autoantibodies in the probands. The prevalence of autoantibodies in spouses of probands who developed their arthritis after marriage showed no difference when compared with that in probands who developed their arthritis before marriage.     

Activation of classical pathway complement in chronic inflammation. Elevated levels of circulating C3d and C4d split products in rheumatoid arthritis and Crohn's disease

Split products of complement component 3 (C3) and complement component 4 (C4) derived from activation of the alternative and classical complement pathways were measured in untreated outpatients, 20 with Crohn's disease and 19 with rheumatoid arthritis. Elevated levels of the d split product of C4 (C4d) were observed in 12 of 19 patients with rheumatoid arthritis and in 9 of 20 patients with Crohn's disease. Levels of the d split product of C3 (C3d) were increased in 14 of 19 patients with rheumatoid arthritis and in 6 of 20 Crohn's disease patients. The median values of C4d and C3d were significantly increased in both groups of patients. C3d concentrations correlated positively with C4d levels (rs = 0.51-0.56, p less than 0.005). The complement activation was not reflected in reduced plasma levels of native C3 and C4. The data indicate activation of the classical complement pathway in both rheumatoid arthritis and Crohn's disease.     

IL-13 results in differential regulation of the complement proteins C3 and factor B in tumour necrosis factor (TNF)-stimulated fibroblasts.

IL-13, like IL-4, a product of activated T cells, has multiple biological actions, primarily on B cells and monocytes. The purpose of the present study was to compare the effects of IL-13 with those of IL-4 on the synthesis of complement proteins in fibroblasts. Dermal fibroblasts were developed from skin biopsies. Confluent monolayers were stimulated with the relevant cytokine or combinations of cytokines and biosynthetically labelled with 35S-methionine. The specific proteins were analysed using immunoprecipitation and SDS-PAGE. Addition of IL-13 to fibroblast cultures treated with TNF-alpha resulted in a dose-dependent increase in C3 protein biosynthesis and a concomitant down-regulation of factor B protein biosynthesis. In TNF-stimulated fibroblasts, the addition of IL-13, 100 ng/ml, induced a 2.45-fold increase in the synthesis of C3, while in the same cells under identical conditions the synthesis of factor B was only 42% of the level without IL-13. Similar effects of IL-13 were noted on IL-1-treated fibroblasts. These effects were specific for C3 and factor B, and no alteration of the constitutive or TNF-induced synthesis of C1s or C1 inhibitor proteins was observed. IL-13 altered the synthesis of C3 and factor B proteins also in fibroblasts stimulated with interferon-gamma (IFN-gamma) in addition to TNF, in the same direction as it did in cells stimulated with TNF alone. IL-13 has similar effects to those of IL-4 on the synthesis of C and factor B in TNF- and IL-1-stimulated fibroblasts. The observed effects of IL-13 are IL-4-independent, as anti-IL-4 antibody abrogates IL-4-induced effects, but has no effect on IL-13-induced responses. This interaction between different cytokines on the synthesis of proinflammatory and immunoregulatory proteins may have significance, particularly at local sites of inflammation, and may affect the synthesis of complement proteins in inflamed joint as in rheumatoid arthritis.