Interplay of immunoglobulin G heavy chain markers (Gm) and HLA in predisposing to systemic lupus nephritis

Immunoglobulin GM and KM genotypes in Korean patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by immune complex deposition. We genotyped immunoglobulin allotypes of G1M (f,z), G2M (n+,n-), G3M (b,g) and KM (1,3) in 142 Korean patients with SLE and 200 healthy controls to investigate the role of the allotypes in SLE. The allele frequency of G1M (z) was significantly higher in patients with SLE as compared to the healthy controls (94.6% vs. 84.3%, corrected P = 0.0004, OR 3.30, 95% CI 1.71-6.88). The frequency of G2M (n-) allele was also higher in patients with SLE (95.3% vs. 88.3%, corrected P = 0.008, OR = 2.71, 95% CI 1.38-5.72). Distribution of the tested allele frequencies for G3M and KM were not different between the patients and controls. In the respect of antibody production, there was increased genotype frequency of G1M (z/z) in anti-Sm(-) SLE (P = 0.023 vs. control, P = 0.042 vs. anti-Sm (+) SLE). In conclusion, particular genotypes at G1M (f,z) and G2M (n+,n-) loci are significantly associated with SLE. These immunoglobulin genes may contribute to the etiology of SLE and production of autoantibodies.

Restriction fragment length polymorphisms of constant region genes of immunoglobulin lambda chains in Venezuelan patients with systemic lupus erythematosus

Previous studies suggest a potential association between human immunoglobulin (Ig) genes and susceptibility to systemic lupus erythematosus (SLE). Ig allotypic determinants seem to confer an increased risk for the disease in various ethnic patient populations. In this study we have examined the pattern of restriction fragment length polymorphisms (RFLP) of constant region lambda (C lambda) light chain genes in a group of 78 Venezuelan patients with SLE and 70 healthy controls. The frequency of the 8-kb allele and the 8/8 genotype was significantly lower in normal Venezuelan controls as compared to healthy British Caucasians (P = 0.0002 and 0.0007 respectively). In turn, Venezuelan controls showed a higher frequency of the 18-kb allele and the 18/18 genotype (P = 0.0002 and 0.0052 respectively). However, there were no statistically significant differences in either parameter between Venezuelan SLE patients and healthy controls. Our study argues against a role for lambda light chain constant region genes in predisposition to SLE.

Immunoglobulin allotypes (GM and KM) and their interactions with HLA antigens in autoimmune diseases: a review

GM and KM immunoglobulin (Ig) allotypes and their interactions with HLA antigens have been analyzed in various autoimmune diseases: multiple sclerosis, rheumatoid arthritis, insulin-dependent diabetes mellitus (IDDM), systemic lupus erythematosus, coeliac disease, Crohn's disease, Graves' disease, atrophic thyroiditis, Hashimoto's thyroiditis, myasthenia gravis, chronic active hepatitis, alopecia areata, uveitis, vitiligo, Turner's syndrome, glomerular nephritis, Berger's disease and idiopathic dilated cardiomyopathy. This review reports published results about associations or linkages, as well as the origins of the populations, the numbers of patients and controls tested. The possible role of Ig polymorphisms in the physiopathology of autoimmune diseases is discussed. Ig allotypes and statistical methods used to analyse the HLA and Ig data are also described.

IgG3 reactive rheumatoid factor in rheumatoid arthritis: etiologic and pathogenic considerations

Rheumatoid factor (RF) is a polyclonal autoantibody directed against the Fc portion of IgG. Although the role of RF in patients with rheumatoid arthritis (RA) is unclear, immune complexes that form between RF and IgG can activate the classical complement (C) pathway, leading to pathogenic outcomes involving inflammatory events and tissue damage. The specificity of serum RF and RF produced by rheumatoid synovial cells (RSC) is different. Serum RF has specificity for rabbit IgG and human IgG subclasses IgG1, 2, and 4, but binds poorly to IgG3. The affinity of serum RF for IgG Fc is low, having an association constant of 10(4)-10(5) M-1. RSC RF, however, has specificity for human IgG and high avidity for IgG3. Because of this greater specificity and avidity for IgG3, and because RSC RF may be pathogenically more important than serum RF, an important role for IgG3-reactive RF in RA may exist. Binding of RF to IgG may be dependent on the allotype and glycosylation of IgG. Infectious agents present in RA patients may directly or indirectly induce the production of certain RF. In this communication, we review and expand on several observations examining the role of IgG3-reactive RF in RA including: 1) binding differences between RF derived from RSC and serum; 2) glycosylation characteristics of IgG and its interaction with RF; 3) apparent allotype dependent binding of IgG3-reactive RF; and 4) possible relationship between infectious agents and the production of IgG3-reactive RF. Taken together, these observations suggest an important role for IgG3-reactive RF in better understanding the etiology and pathogenesis of RA.

Differences in HLA antigens between patients with mixed connective tissue disease and systemic lupus erythematosus

Patients with mixed connective tissue disease (MCTD, n = 32) or systemic lupus erythematosus (SLE, n = 60) were typed for HLA-A, B, C, Dw, and DR antigens. All patients with SLE fulfilled at least four criteria of SLE and the patients with MCTD met the criteria proposed by Alarcon-Segovia (1989). The presence of antibodies to Sm was not considered as an exclusion for MCTD. In the patients with SLE, Dw3, DR3, and the associated B8 and A1 antigens were increased, whereas in the patients with MCTD an increased frequency of Dw4 was found (45 v 18% in controls v 14% in SLE). Of the subtypes of DR4, Dw4 was present in all but one of the DR4 positive patients. The frequency of DR4 in patients with MCTD (52%) differed significantly from that of controls (28%). The strong association of MCTD to one DR4 subtype was further seen in the significantly increased frequency of the B15, DR4 combination. Thus the genetic background seems to be different in patients with MCTD from that in patients with SLE. This could partly explain the clinical differences between these diseases.

Immunoglobulin heavy chain constant-region gene polymorphism in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is associated with immunoglobulin allotypes in several ethnic groups. In this study, we investigated the association of a Bst EII immunoglobulin heavy chain constant-region gene restriction fragment length polymorphism with SLE in patients from the US and Mexico. A 3-kb restriction fragment was observed with significantly decreased frequency in randomly selected Mexican SLE patients and in Mexican SLE patients in multiplex families. However, no such association was observed in SLE patients from the US. Thus, the absence of a 3.0-kb Bst EII restriction fragment from immunoglobulin heavy chain constant-region genes provides a marker for SLE in Mexican individuals.

Immunoglobulin allotypes are not associated with HLA-antigens, autoantibodies and clinical symptoms in systemic lupus erythematosus. Members of the SLE Study Group

Immunoglobulin heavy chain (G1m, G2m, G3m, A2m) and kappa light chain (Km) allotype and phenotype frequencies of 323 central European Caucasian patients with systemic lupus erythematosus (SLE) were examined and correlated with various genetic, serologic and clinical markers of SLE. No significant associations were found between immunoglobulin allotypes or phenotypes and all 20 parameters tested (nephritis, vasculitis, arthralgias, photosensitivity, discoid lesions, central nervous system disease, Raynaud's phenomenon, sex, anti-Ro, anti-La, anti-nRNP, HLA-DR1-DR7, HLA phenotypes B8-DR3, B7-DR2). It could therefore be assumed that Gm, A2m and Km allotypes were not associated with HLA-antigens and had no influence on the serologic and clinical expression of SLE.

Association of immunoglobulin Km and Gm allotypes with specific antinuclear antibodies and disease susceptibility among connective tissue disease patients

The distribution of the immunoglobulin Km(1) and Gm phenotypes was examined in patients with connective tissue diseases, including systemic lupus erythematosus, mixed connective tissue disease, and scleroderma, whose sera were characterized for antibodies against nuclear antigens and polypeptides of U small nuclear ribonucleoproteins. We found a strong association between Km(1) phenotype and susceptibility to systemic lupus erythematosus (P less than 0.00001, relative risk = 17). We also found a positive association between the Km(1) phenotype and the presence of anti-double-stranded DNA antibodies. The presence of certain immunoglobulin genes or gene families may have a role in susceptibility to the development of autoantibodies and/or of connective tissue disease.

Non-H-2 genes alter the H-2 determined susceptibilities in immune complex nephritis

These experiments examined the effects of genes outside of the H-2 region on disease susceptibility and pathogenesis. Four strains of mice with the susceptible H-2 type, H-2d, but different non-H-2 genes were studied. B10, D2, Balb/c, NZB, and DBA/2J mice were injected with 4 mg of apoferritin i.p. q.d. for 28 days. B10, D2 and Balb/c mice developed proliferative and crescentic glomerulonephritis. NZB mice developed proliferative and crescentic glomerulonephritis with wire loop lesions suggestive of lupus. DBA/2J mice developed only minimal mesangial proliferation without crescents or necrosis. Electron microscopy showed subepithelial and mesangial deposits in B10, D2, moderate subepithelial and mesangial deposits in Balb/c, and marked mesangial, subendothelial and subepithelial deposits in NZB. Immunofluorescence demonstrated the presence of IgG, IgM, C3 and apoferritin in these deposits. The DBA/2J mice had only minimal mesangial deposits by immunofluorescence and electron microscopy. These experiments demonstrate that non-H-2 genes alter the H-2d determined disease susceptibility seen in H-2 congenic mice. NZB genes can alter the disease so that lupus-like lesions develop and DBA/2J genes can substantially ameliorate the disease.

Gm allogenotype distribution and lack of HLA-DR, Gm interaction in SLE and CREST/PSS

The distribution of Gm allogenotypes (Gm allotypes identified by IgCH restriction fragment length polymorphism (RFLP) analysis) was compared in 66 systemic lupus erythematosus (SLE) patients, 38 CREST/PSS group (P less than 0.05) but not in the SLE group. HLA-DR5 is significantly increased in frequency in this series of CREST/PSS patients compared to controls (P less than 0.001), and log linear regression analysis showed that although both DR5 and Gm homozygosity were significant factors determining disease susceptibility, there was no evidence of an interactive effect between these two groups of genes increasing the predisposition to CREST/PSS.

Genetic factors in Graves' ophthalmopathy

We investigated the distribution of HLA and immunoglobulin G heavy chain markers (Gm) in 117 patients with Graves' disease, 62 with ophthalmopathy and 55 without. With Graves' disease per se, there is a closer association with HLA-DR3 than with B8. The opposite was true for Graves' patients with ophthalmopathy (odds ratio for ophthalmopathy associated with B8 was 12.4 and with DR3 was 7.7, both with P less than 0.0005). HLA-DR7 interacts with B8 in modifying the risk for eye disease; using the phenotype B8- DR7- as reference, the odds ratios were 16.7 for B8+ DR7+, 8.7 for B8+ DR7- and 0.26 for B8- DR7+. Thus, DR7 enhanced the risk for ophthalmopathy in the presence of B8+ but had a protective influence in its absence. Although Gm showed no association with eye disease, it modified the risk for ophthalmopathy associated with HLA-B8; the odds ratios were 20.9 for B8+ Gmfb homozygozity (fb+), 15.3 for B8+ fb- and 1.7 for B8- fb+ (B8- fb- = 1.00). We conclude that the genetic factors contributing to Graves' ophthalmopathy are different from those related to liability for Graves' hyperthyroidism.

Heterogeneity of systemic lupus erythematosus elucidated by cluster analysis. The influence of HLA

For 75 patients with systemic lupus erythematosus (SLE), 39 laboratory and clinical characteristics, including HLA-A, B, C and DR typing, were analysed using a cluster analysis technique. Three groups were identified. Group I (46 patients) was characterized by infrequently severe disease, good response to therapy and infrequent multisystem involvement. Group II (24 patients) was characterized by a severe course of disease (although the tendency to remit after therapy was not unusual), and frequently, renal involvement and pericarditis. Group III (5 patients) was characterized by more severe renal disease. Of the 75 patients studied, 38.7% possessed HLA-DR3, compared to 17.4% of controls. Group I patients did not differ from controls but 80% of Group II patients and 4/5 Group III patients had DR3. Cluster analysis identifies subsets of SLE patients who show marked differences in disease course and severity, correlated with possession of the HLA B8, DR3 phenotype.