High levels of in vitro IgM rheumatoid factor synthesis correlate with HLA-DR4 in normal individuals

The levels of memory (CD45RA-, RO+) CD4+ and CD8+ peripheral blood T-lymphocytes correlate with IgM rheumatoid factors in rheumatoid arthritis

We investigated whether, in rheumatoid arthritis (RA), the CD45 isoform expression of peripheral blood T-lymphocytes (T-PBL) is related to auto-immune processes (e.g. IgM rheumatoid factors) and to clinical manifestations. By three-colour flow cytometry, we quantified three subsets of CD4+ or CD8+ T-PBL: "naive" CD45RA+,RO-, "transient" CD45RA+,RO+, and "memory" CD45RA-,RO+ cells, in 102 patients with RA and in 41 age- and sex-matched controls. The serum levels of rheumatoid factors (RF) were determined--besides conventional agglutination tests--by ELISA (IgM-RF). Extensive clinical examination was performed at the time of blood sampling. In RA, age, sex and drug therapy did not constitute major influences on the CD45RA/RO patterns. In "healthy" men, higher age significantly' correlated with fewer naive and more memory CD4+ T-PBL (P < 0.01). In RA, distinct correlations between the T-PBL subsets, autoimmune and clinical manifestations became obvious when patients with low and high levels of RF against human IgG Fc fragments, as determined by ELISA, were analysed separately. RA patients with high IgM-RF had elevated proportions of CD45RO+ T-PBL (P < 0.05), that correlated with clinical parameters of disease activity (tender joint count, Ritchie index, P < 0.05) and outcome (Health Assessment Questionnaire, Larsen radiographic scores, P < 0.05). The proportions of memory CD4+ and CD8+ T-PBL correlated strongly (P < 0.001) with the IgM-RF levels. Within 1 year, only three of 34 patients (disease duration of 5-9 years) showed seroconversion from low to high levels of IgM-RF (and positive agglutination tests); this was paralleled by reductions in naive and increases in transient T-PBL (P < 0.02). Thus, in RA, the proportions of memory CD4+ and CD8+ T-PBL correlate with the level of IgM-RF and, together with transient T-PBL, with clinical parameters of disease activity and outcome.

Composition and biological behaviour of immune complexes isolated from synovial fluid of patients with juvenile rheumatoid arthritis (JRA)

Data published from in vitro studies have shown that IgM-rheumatoid factor (RF)-bearing immune complexes possess several biological features that may contribute to their pathogenicity. However, no studies have demonstrated that such complexes exist at sites of inflammation in children with rheumatoid disease. We used two methods of sequential column chromatography to purify immune complexes from synovial fluids of children with JRA. We demonstrate that high molecular weight complexes contain IgM-RF, have not bound C4 in vivo, but activate the classical pathway in vitro. In contrast, complexes which have bound C3 in vivo do not contain IgM-RF and are weak complement activators in vitro.

Interactions of synovial fluid immunoglobulins with chondrocytes

OBJECTIVE

To study the interaction of synovial fluid (SF) immunoglobulins with living chondrocytes, and to evaluate the relative contribution of type II collagen (CII) antibodies.

METHODS

SF of patients with rheumatoid arthritis (RA), osteoarthritis (OA), and gout were incubated with isolated bovine articular chondrocytes. Ig binding was measured by flow cytometry and by quantitation with 125I-labeled anti-IgG and anti-IgM. Complement-dependent cytotoxicity was determined by 51Cr release. Immunoglobulin binding and cytotoxicity were compared between chondrocytes obtained from the superficial and from the deep cartilage zones.

RESULTS

Significantly greater IgG and IgM binding was found with RA SF compared with OA or gout SF. Chondrocytes bound more Ig than did fibroblasts. The relative contribution of anti-CII antibodies to Ig binding was studied following absorption of the SF with bovine CII, and by incubation with bacterial collagenase-treated chondrocytes. There was a small but significant reduction in IgG and IgM binding with SF samples that were positive for anti-CII. RA SF exhibited modest, but significantly greater complement-dependent cytotoxicity than OA SF: Gel chromatography fractionation indicated that IgM antibodies were responsible for the cytotoxic activity. Additional studies showed that SF IgM antibodies bound preferentially to, and killed chondrocytes obtained from, the superficial layers of cartilage.

CONCLUSION

Anti-CII antibodies contained in RA SF represent one of many antibody specificities reacting with chondrocyte membrane antigens. Chondrocyte-reactive SF antibodies may play an important pathogenic role in the processes leading to irreversible cartilage damage in RA. These deleterious effects appear to be exerted particularly on chondrocytes located near the articular surface of cartilage.

The relationship between circulating CD5+ B lymphocytes and in vitro autoantibody synthesis in normal individuals

Recent observations suggest that a subpopulation of B lymphocytes bearing the phenotype CD5+ may be enriched for cells committed to the synthesis and secretion of autoantibodies. We had previously shown that a subset of normal individuals has an expanded subpopulation of B lymphocytes committed to the synthesis of IgM and IgM-rheumatoid factor (RF), and that this condition was associated with HLA-DR4 (4). In these studies, we performed simultaneous quantitation of the size of the circulating CD5+ B lymphocyte subpopulation in a group of 20 normal donors, and of the pokeweed mitogen-induced in vitro synthesis of a panel of autoantibodies by the same peripheral blood cells depleted of CD8+ suppressor lymphocytes in 18 of the 20 individuals. The culture supernatants were assayed for total IgM and IgG, RF, IgM, and IgG anti-single-stranded DNA, anti-human thyroglobulin, and anti-tetanus toxoid. The mean percentage CD5+ B cells was 13.5 +/- 2.5%. There was no significant correlation between total B lymphocytes and CD5+ B cells (R = 0.25, P greater than 0.20. Positive correlations were found between the proportion of circulating CD5+ B lymphocytes and synthesis of RF (R = 0.73, P less than 0.001), and IgM anti-DNA (R = 0.58, P less than 0.03). Significant correlations were not found between CD5+ B cells and secreted IgM or IgG antibodies against the exogenous antigen tetanus toxoid, measured in the same supernatants. The antibodies produced in vitro by T cell-dependent B cell activation appear to have limited or no polyspecificity. These results indicate that the size of the circulating CD5+ B cell subpopulation in any given individual contributes importantly to the magnitude of autoantibody synthesis in cultures where T cell-mediated B lymphocyte activation takes place in the absence of suppressor signals.

Rheumatoid arthritis

The results of family and twin studies suggest that RA may result from an interaction between an oligogenic susceptibility and unknown environmental factors. Part of this genetic predisposition is accounted for by genes within the MHC where there is a well-documented association with HLA-DR4. Studies of DR and other MHC variants have shown different associations with particular subgroups. One subgroup is Felty's syndrome where there is a strong association with DR4, as well as associations with DQ-beta and C4B null variants when DR4-matched Felty's and RA subjects are analysed. These DQ-beta and C4B null variants may characterize a single haplotype which is associated with extra-articular disease. A further rheumatoid subgroup characterized by circulating antibodies to native type II collagen, shows an association with HLA-DR3 and 7. Genes on chromosome 14 may also influence susceptibility to RA, probably by interaction with MHC genes and there are different Gm associations for DR4-positive and collagen-antibody-positive rheumatoid subgroups. HLA and Gm markers so far identified only account for a small part of the total genetic predisposition to RA and a third or further loci may also be involved. Possible candidates include T-cell alpha- and beta-chain genes and immunoglobulin light chain genes. One present concept of the genetic predisposition to RA is of several independent immunogenetic pathways each including interactions at two or more loci.

The incidence of rheumatoid arthritis is predicted by rheumatoid factor titer in a longitudinal population study

Rheumatoid factor (RF) is often detected in subjects who do not have rheumatoid arthritis (RA). To determine if the presence of RF is predictive of the development of RA, 2,712 Pima Indians of Arizona, 20 years of age or older, initially without RA, have been observed for up to 19 years with biennial examinations. These included a medical history, physical examination of the joints, radiographs, and RF determination by sheep cell agglutination test. During the study period, 70 new cases of RA developed. When the population at risk was stratified by RF titer, with reclassification at subsequent examinations if the RF titer changed, the age- and sex-adjusted incidence of RA increased with higher titers of RF. The incidence of RA (in cases per 1,000 person-years) according to RF titer was 2.4 (RF titer less than 1:2); 6.7 (titer 1:2-1:16); 11.0 (titer 1:32-1:256); and 48.3 (titer greater than 1:256) (P less than 0.001). The same trend was also found within each age and sex group, and within groups defined by the number of American Rheumatism Association criteria present before the definite diagnosis. We conclude that the presence of RF, in subjects without RA, is a risk factor for the development of RA, and that this risk is related to the RF titer. It is also suggested that RF may represent a marker of the earliest phases of the pathogenetic process of RA, that may be detectable before the appearance of other features that permit a clinical diagnosis.

Associations of HLA-DR4 with rheumatoid factor and radiographic severity in rheumatoid arthritis

Possible associations between HLA-DR4 and laboratory, radiographic, joint count, functional, and demographic measures of clinical status were analyzed in 154 white patients with rheumatoid arthritis. Overall, 65 percent of the patients were HLA-DR4 positive, similar to other series. HLA-DR4 was associated significantly with the presence of rheumatoid factor and more severe radiographic changes. HLA-DR4 was not associated with significant differences in demographic, joint count, or functional measures of clinical status. HLA-DR1 was not associated significantly with differences in the presence of rheumatoid factor, radiographic changes, or other measures of clinical status. Selective associations of HLA-DR4 with rheumatoid factor and radiographic scores were more marked in men than in women. Patients who were putatively homozygous for HLA-DR4 were all seropositive and had more severe radiographic changes than patients who were heterozygous for HLA-DR4.

Epidemiological and genetic aspects of IgM rheumatoid factors

The occurrence of IgM rheumatoid factors (RF) was studied in a random sample of 8807 persons aged between 20 and 50 years in Tromsø, North Norway. Seropositivity for IgM RF was defined as a Waaler titre of 40 or more. A total prevalence of IgM RF of 1.36% was found, and a prevalence between 0.48-0.94% was found among the healthy persons, with no sex difference. Approximately 50% of IgM Rf positives are thus healthy. Only 11% of those with IgM RF suffered from rheumatoid arthritis. The majority of RF positive sera from healthy persons were low titred, and 81% of them converted to seronegativity in the course of 3.5 years. A low titred IgM RF appears rather harmless, while a high titre indicates a specific disease process. No association between IgM RF and DR4 could be found in healthy persons. The frequencies of Gm-allotypes a, b, e, f-n and x in healthy, RF positive individuals did not differ from the RF positive patients with RA, suggesting that the Gm-allotypes are not involved in the genetic pre-disposition for RA.