Analysis of IgG subclasses of human antitopoisomerase I autoantibodies suggests chronic B cell stimulation

Screening for IgG4-type anti-nuclear antibodies in IgG4-related disease

BACKGROUND

Immunoglobulin (Ig) G4-related disease (IgG4-RD) is characterized by elevated serum IgG4 and infiltration of IgG4(+) plasma cells into multiple organs. It is not known whether serum IgG4 is autoreactive in IgG4-RD.

METHODS

We measured anti-nuclear antibody (ANA) in 19 IgG4-RD cases, determined IgG subclasses of the ANA, and compared them with those of other systemic autoimmune diseases (systemic lupus erythematosus, Sjögren's syndrome, systemic sclerosis, and polymyositis), using subclass-based ANA test (indirect immunofluorescence).

RESULTS

58 % of IgG4-RD cases were ANA-positive (cut-off: 1:40). Whereas their subclass of ANA was predominantly IgG2, we observed no IgG4-type ANA. In systemic autoimmune diseases, subclasses of ANA were mostly IgG1, 2, or 3, but IgG4-type ANA was very rarely detected. We also found several patients in whose serum ANA patterns differed among IgG subclasses, probably due to the difference of corresponding autoantigens.

CONCLUSIONS

Although IgG4 is highly elevated in sera of IgG4-RD patients, their ANA do not include IgG4 subclass. These results offer new insight into the role of IgG4 and the pathogenesis of IgG4-RD, implying that each IgG subclass tends to cover its own spectrum of antigens, and IgG4 is not preferentially used to make ANA.

Correlation of serum anti-DNA topoisomerase I antibody levels with disease severity and activity in systemic sclerosis

OBJECTIVE

To investigate correlations between serum levels of topoisomerase I-specific antibody (anti-topo I) and clinical features of systemic sclerosis (SSc), including disease severity (the total skin score [TSS]) and disease activity.

METHODS

Using highly sensitive enzyme-linked immunosorbent assays, we measured the levels of anti-topo I antibody, including total IgG, individual IgG subclasses, and IgA, and analyzed their correlations with the TSS in 59 patients with SSc, all of whom had diffuse cutaneous involvement. Serial serum samples were obtained from 11 of these patients.

RESULTS

The titers of anti-topo I antibody, including IgG and IgA, were positively correlated with the TSS, a measure of SSc disease severity. In 8 of the 11 patients from whom serial serum samples were obtained, changes in the levels of both IgG and IgA, when detectable, paralleled changes in the TSS. In 3 patients, an increasing anti-topo I IgG level preceded an increase in the TSS. The level of each IgG subclass also correlated with and tended to parallel the TSS. The patients with very active disease had higher mean IgG (P < 0.001) and IgA (P < 0.05) titers than did those with inactive disease.

CONCLUSION

Serum levels of anti-topo I antibody correlate positively with disease severity and disease activity in SSc.

Clinical features and IgG subclass distribution of anti-p80 coilin antibodies

We examined the clinical features of patients presenting antinuclear autoantibodies against p80-coilin and the IgG subclass distribution of anti- p80-coilin antibodies. Sera from 365 Japanese patients were analysed. Immunoblotting and indirect immunofluorescence microscopy techniques were used with a polyclonal rabbit antiserum against p80-coilin. Eleven patients with anti-p80-coilin antibodies were found. All the patients were female and nine were in their twenties. None could be diagnosed with differentiated rheumatic disease except for one case of systemic scleroderma and another of Sjögren's syndrome. Most patients had general fatigue, arthralgia, headaches, dysmenorrhea, lymph node swelling and/or low grade fever such as chronic fatigue syndrome (CFS), and showed low complement. One patient fulfilled the criteria for CFS. All were younger females than those often diagnosed with rheumatic disease in previous reports. Patients' sera had a predominant distribution of subclass IgG(1)anti-p80-coilin antibodies and five sera had concomitant subclass IgG(2). Two rheumatic disease patients had a relatively high titer of IgG(2)anti-p80-coilin antibodies. The IgG(2)subclass of anti-p80-coilin antibodies may be a specific marker for systemic autoimmune disease.

Anticentromere autoantibodies in patients without Raynaud's disease or systemic sclerosis

Anticentromere autoantibodies (ACA) are associated with Raynaud's disease and systemic sclerosis (SSc). ACA usually bind at least one of three major centromere proteins (CENPs), particularly CENP-B. We identified 16 patients with ACA who do not have Raynaud's disease or SSc. The objective of this study was to determine whether these 16 ACA differ in antigenic specificity from the ACA found in patients with Raynaud's disease or SSc. Binding of these serum ACA was tested using competition experiments with recombinant CENP-B, and native centromere proteins from HEp-2 cells and HeLa nuclear extracts in ELISAs, immunoblots, and indirect immunofluorescence assays. The ACA from these 16 patients are strikingly different from those obtained from patients who have Raynaud's disease or SSc. Only 5 of the 16 index sera (31.25%) bound CENP-B from two or more different sources by at least two methods. Six of these 16 sera (37.5%) did not bind CENP-B on ELISA, and 8 of 16 (43.75%) did not bind CENP-B on immunoblots. Three sera did not bind CENP-B either by ELISA or immunoblots. Of the 13 sera that bound CENP-B, their patterns of binding to CENP-B strongly suggested that they bind different epitopes within the CENP-B antigen. Independently of their binding to CENP-B, these sera reacted mainly with minor CENP antigens detected by HeLa nuclear extracts. We have identified unusual ACA not associated with Raynaud's disease or SSc.