The frequency of circulating immune complexes in rheumatoid arthritis and systemic lupus erythematosus

Vasculitis associated with connective tissue disease

Vasculitis, one of the clinical features shared by connective tissue diseases, should be considered when signs and symptoms are observed that may result from tissue ischaemia due to damaged vessels. The lesions seem to result from specific and non-specific immunopathogenic mechanisms targeted at the vascular endothelium. Because of the therapeutic implications it is the physician's responsibility to document its presence and the extent of organ involvement. Prompt institution of immunosuppressive drugs may be lifesaving. On the other hand there are some forms of vasculitis accompanying connective tissue disease which are entirely benign. Patients with infarctions of extremities and progressive functional disturbances of the central nervous system or internal organs because of vasculitis should be treated with high dosages of corticosteroids in combination with cytostatic drugs. Remissions are frequently obtained within three to six months of initiation of treatment and can be maintained with a less aggressive treatment regimen.

Immune complex specific for the pancreatic duct antigen in patients with idiopathic chronic pancreatitis and Sjögren syndrome

Circulating immune complexes (ICs) containing the pancreatic antigen against SP3-1 monoclonal antibody were measured in patients with idiopathic chronic pancreatitis (ICP) and Sjögren syndrome (SjS) by Raji cell and solid-phase radioimmuno-assays (RIA). The mean serum levels of ICs measured by solid-phase RIA were significantly higher in patients with ICP (n = 23) and SjS (n = 21) than control (n = 15, p < 0.05, p < 0.02, respectively). ICs were positive in 10 patients with ICP (43%) and 12 SjS patients (57%). Raji cell assay also revealed a significantly higher serum ICs levels in patients with ICP (n = 17) and SjS (n = 12) compared with those of control (n = 7, p < 0.025, p < 0.005, respectively). Seven patients with ICP (41%) and 8 SjS patients (67%) had positive ICs. This was in contrast to the normal level of ICs in patients with alcoholic chronic pancreatitis, primary biliary cirrhosis, and chronic thyroiditis. Our analysis demonstrated a significant and positive relationship between RIA and Raji cell assay (r = 0.70, p < 0.05). Our results suggest that ICs specific for SP3-1 may play a role in the pathophysiology of ICP and SjS.

Immunoglobulin isotype composition of circulating and intra-articular immune complexes in patients with inflammatory joint disease

The immunoglobulin (Ig) heavy chain isotype composition of intra-articular and circulating immune complexes (ICs) were determined by a Raji cell flow cytometric assay in paired serum and synovial fluid samples from 15 patients with rheumatoid arthritis (RA) and 15 patients with other articular diseases (osteoarthritis, ankylosing spondylitis, gout, psoriatic arthritis, Reiter's disease). ICs were most prevalent in synovial fluid samples of patients with RA but were infrequently detected in serum and synovial fluid samples from the non-RA patients. ICs in patients with RA were heterogeneous both in the prevalence of Ig subclasses identified and in the distribution of the respective Ig isotypes within the complexes. Furthermore, differences were observed in the Ig isotype composition of ICs in paired serum and synovial fluid samples indicating that circulating ICs may not always arise simply by spill-over from articular sites. The possible mechanisms for IC formation in RA are discussed with reference to four patients who displayed features of extra-articular disease.

Degradation of aggregates of activated C3 (C3b) by monocytes of patients with rheumatoid arthritis is related to vasculitis

We investigated whether a decreased complement receptor expression or function of monocytes isolated from peripheral blood of 52 patients with rheumatoid arthritis (RA) and rheumatoid vasculitis (RV) could account for the previously observed diminished degradation of immune complexes by monocytes of patients with RA and RV. On average, monocytes from all patients expressed significantly less CR1, and degraded significantly less AC3b when compared with monocytes of healthy controls. In addition, monocytes from RV patients degraded significantly less AC3b when compared with monocytes from patients with RA. The expression of both CR1 and CR3 on monocytes of RV patients was lower compared with RA patients but this difference was only significant for CR3. No differences were found between AC3b degradation and the expression of CR1 and CR3 between patients with active and inactive RA. Using linear discriminant analysis on the variables AC3b, CR1 and CR3, 94% of the patients could be classified correctly as healthy controls, RA or RV, suggesting a true multi-variate relationship between these parameters and patients groups. Our results suggest that the diminished capacity of monocytes from RA patients to degrade AC3b is due partly to a decreased expression of CR1 and CR3.

C3-containing serum immune complexes in patients with systemic lupus erythematosus: correlation to disease activity and comparison with other rheumatic diseases

Although testing for circulating immune complexes (CIC) is regarded as a useful, complementary, laboratory parameter in the differential diagnosis and management of immune complex-induced vasculitis syndromes, there is still an uncertainty with regard to assay systems used for the demonstrated of soluble immune complexes. This is partly due to difficulties in the reproducibility, handling and principle limitations of available test systems for the assessment of soluble immune complexes in body fluids. In the present communication a modification of the anti-C3 test for the determination of CIC was developed using nitrocellulose as a solid phase matrix. IgG-, IgA- and IgM-containing CIC were determined and quantified using standard immune complex preparations. When 39 sera of SLE patients, 12 sera of patients with vasculitis syndromes, 10 sera of rheumatoid arthritis patients and 11 sera of patients with ankylosing spondylitis were tested, predominantly IgG-containing CIC could be demonstrated. Only in SLE patients was a significant amount of other immunoglobulin isotypes detected in CIC. In these patients a significant difference of IgG-containing CIC levels was found with regard to patients with high and low disease activity (P less than 0.0001). A significant correlation was also established between IgG-containing CIC and anti-dsDNA antibodies (P less than 0.001). In a longitudinal study the isotypes in the isolated CIC were found to be constant.

Antibodies to the collagen-like region of C1q in sera of patients with autoimmune rheumatic diseases

Antibodies to the collagen-like region of C1q have recently been observed in sera of patients with systemic lupus erythematosus (SLE). In this study, we documented that these antibodies were present in 47.3% of SLE patient sera, whereas they were uncommon in sera from patients with rheumatoid arthritis (2.8%) and Sjögren's syndrome (12.8%), as well as in normal sera (6.4%). Markedly elevated antibody levels (greater than 4 SD above the normal mean) were observed almost exclusively in sera of patients with SLE. Levels of antibodies to the collagen-like region correlated highly with levels of solid-phase C1q-binding IgG when analyzed by the C1q solid-phase assay for immune complexes (r = 0.87). We previously found that, after sucrose density gradient ultracentrifugation, a predominance of the solid-phase C1q-binding IgG in SLE sera sediments as monomeric IgG. These findings, together with the present data, indicate that reactivity of SLE patients' sera in the C1q solid-phase assay reflects primarily the presence of antibodies to the collagen-like region, and not the presence of immune complexes.

Immune complexes in sera from patients with rheumatoid vasculitis induce polymorphonuclear cell-mediated injury to endothelial cells

The ability of sera from 11 patients with rheumatoid arthritis (RA) complicated by leukocytoclastic vasculitis (RV) to induce injury to cultured monolayers of human umbilical vein endothelial cells (HEC) was investigated. Injury was assessed in vitro using assays of cell lysis and cell detachment. Sera from patients with RV produced neither direct injury to HEC monolayers nor indirect injury when cocultured with HEC and normal peripheral blood polymorphonuclear cells (PMN). However, immune complexes (Icx) isolated from these sera induced nonlytic PMN-mediated HEC detachment. The inhibitory effect of serum on PMN-mediated HEC detachment induced by Icx could be attributed both to a different response of PMN to Icx present in serum compared to isolated Icx and to the presence of protease inhibitors in serum. The results of this study show that sera from patients with RV do not contain factors that can injure HEC directly and provide further support for the hypothesis that Icx and PMN play important roles in the pathogenesis of immune vascular injury.

Anti-C1q affinity isolated circulating immune complexes correlate with extra-articular rheumatoid disease

Circulating immune complexes (CIC) were isolated from sera of 35 patients with rheumatoid arthritis (RA) by a two-step method using 2% polyethylene glycol precipitation and anti-C1q affinity chromatography. By this method CIC were exclusive to 19 patients with vasculitis, nodules, or Sjögren's syndrome. Levels of CIC did not correlate with the severity of synovitis but reflected the extent of extra-articular disease. Furthermore, in four patients with persistent severe synovitis observed over a period of 4 to 16 months, the levels of CIC paralleled changes in extra-articular disease. Despite such additional evidence, whether the relationship between CIC and tissue injury is causative or consequential remains unresolved.

HLA antigen associations with extra-articular rheumatoid arthritis

Seventy-seven patients with rheumatoid arthritis were investigated to examine the frequency of HLA antigens and their relationship to clinical and serological manifestations of extra-articular disease. The phenotype frequencies of DR4, DRw53, Bw62 and Cw3 were significantly increased, compared to normal controls, and there were negative associations with DR2 and DR7. The HLA antigen in strongest association with rheumatoid arthritis was DR4 (73.6%) and the relationship with DRw53 appeared to be secondary. The frequency of DR4 rose to 92% in seropositive patients with extra-articular disease manifestations whose serum contained immune complexes. A high frequency of DR4 was also seen in male patients (86%), reaching 100% in the small group of seropositive male patients with immune complexes. It is suggested that extra-articular disease represents a manifestation of severe classical rheumatoid arthritis and is not an 'overlap' syndrome. We propose that the HLA haplotype Cw3-Bw62-Dw4-DR4-DRw53 makes a greater genetic contribution to disease susceptibility in both extra-articular and male rheumatoid arthritis patients than in other subsets of RA.