Subclass restriction and polyclonality of the systemic lupus erythematosus marker antibody anti-Sm

Distribution of IgG subclass anti-nuclear antibodies (ANAs) in systemic lupus erythematosus

OBJECTIVES

Our study purpose was to detect the distribution of anti-nuclear antibody (ANA) IgG subclasses in patients with systemic lupus erythematosus (SLE) and to evaluate their influence on the inflammatory process in SLE.

METHODS

We determined the serum levels of ANA IgG subclasses from 70 SLE patients, 25 patients with other autoimmune diseases (OAD), and 25 healthy controls using ELISA. The serum level of total ANA IgG and the avidity of ANA IgG, dsDNA IgG, and dsDNA IgG subclasses were analysed by ELISA.

RESULTS

The results indicated that levels of four ANA IgG subclasses (IgG1, IgG2, IgG3 and IgG4) and total IgG were significantly higher in SLE patients than in OAD patients and healthy controls (p < 0.001). Moreover, the level of each ANA IgG subclass and the prevalence of high-avidity IgG ANAs (HA IgG ANAs) were significantly higher in the active cases than in the inactive cases of SLE and LN. Furthermore, level of ANA IgG subclasses decreased as level of dsDNA IgG subclasses decreased in 30 patients with SLE. In comparison, ANA IgG3 was significantly effective in high-dose prednisone combined with hydroxychloroquine (p = 0.025). Additionally, it revealed that level of dsDNA IgG had a significant influence on four ANA IgG subclasses, especially on ANA IgG3 (β coefficient = 0.649, p < 0.001). Level of ANA IgG3 was also positively related to the serum level of dsDNA IgG (r = 0.729, p < 0.001) and RAI of HA IgG ANAs (r = 0.504, p < 0.001). However, the level of ANA IgG4 was positively related to the serum level of albumin (r = 0.572, p < 0.001) and RAI of HA IgG ANAs (r = 0.549, p < 0.001). Moreover, the results revealed that cutaneous and renal involvement were mainly associated with the ANA IgG1 and IgG4 subclasses. Although, arthritic involvement was mainly associated with ANA IgG3.

CONCLUSIONS

First, we demonstrated that the ANA IgG subclasses were diagnostic tools in SLE patients. Furthermore, HA IgG ANAs might affect the distribution of ANA IgG3 and IgG4. Moreover, ANA IgG3 might play a particular role in the activity of SLE disease and therapy. Therefore, an altered ANA IgG subclass distribution might be a risk factor influencing the inflammatory process in SLE.

Progression of immunoglobulin G4-related disease to systematic lupus erythematosus after gastric cancer surgery: A case report

RATIONALE

Immunoglobulin G4 related disease (IgG4-RD) rarely coexists with other autoimmune diseases, though we had a patient whose primary clinical problem was shifted from IgG4-RD to systemic lupus erythematosus (SLE) after gastrectomy. The present paper aimed to report pathological findings and clinical course of the patient.

PATIENT CONCERNS

The patient was a male aged 74 years old with gastric cancer characterized by the following symptoms: Raynaud phenomenon, polyarthralgia, and swollen parotid glands on both sides. Before gastrectomy, laboratory examination results showed renal dysfunction, hypocomplementemia, antinuclear antibodies (ANAs) positivity, and elevated serum IgG and IgG4 levels.

DIAGNOSIS

Based on postoperative renal biopsy showing severe plasma cell infiltration with tubulointerstitial fibrosclerosis, the patient was diagnosed with IgG4-RD. Despite significant improvement in renal function and reduction in parotid gland swelling during the postoperative follow-up period, after 7 months of the gastrectomy, anti-DNA antibody levels were increased and serositis was detected, which indicated the onset of SLE. IgG4-type ANA were also detected in the sera of the patient.

INTERVENTIONS

Treatment by oral prednisolone at 30 mg/day was initiated.

OUTCOMES

Pericardial fluid, pleural effusions, and thickening of the gallbladder wall improved after 3 months of treatment according to computed tomography.

LESSONS

This study presented a rare case of comorbidity, wherein the patient's primary problem progressed from IgG4-type ANA-positive IgG4-RD to SLE after excision of gastric cancer.

Complement-fixing properties of antinuclear antibodies distinguish drug-induced lupus from systemic lupus erythematosus

The immunofluorescence antinuclear antibody (ANA) test has been widely used to monitor autoimmune disease, but its value for diagnostic purposes is compromised by low specificity and high prevalence in disease-free individuals. The capacity of autoantibodies to fix serum complement proteins when bound to antigen is an important effector function because this property is associated with acute and chronic inflammatory processes. The current study evaluates the complement-fixing properties of antinuclear antibodies (CANA) in three well-defined and clinically-related patient groups: systemic lupus erythematosus (SLE), drug-induced lupus (DIL) and drug-induced autoimmunity (DIA). Of 20 patients diagnosed with SLE, 90% displayed complement-fixing ANA while this feature was present in only two of 18 patients with DIL and no patients with DIA without associated disease even though the mean ANA titres were similar among these patient groups. CANA was significantly correlated with anti-Sm activity. Because SLE but not DIL or DIA can be a life-threatening disease associated with complement consumption in vivo, these results demonstrate that measurement of CANA is a diagnostically useful tool and may have immunopathologic implications.

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.

Strategies for building reference standards for autoantibodies

Producing robust, certified, traceable reference material for autoantibody testing is a vital element in maintaining the validity of results that are generated in the daily clinical laboratory routine. This is a huge challenge because of the high number of variables involved in the detection and measurement of the autoantibodies. The production of such materials is time consuming and needs rigorous attention to detail; this is best achieved by an overarching independent body who will oversee the process in a “not for profit” manner. Much effort has been made to build international standards for quantitative and qualitative assays based on monoclonal antibodies, obtained from affinity purification and plasmapheresis. The big challenge is to respect individual differences in immune response to the same antigen. A promising ongoing initiative is the construction of pools with monospecific samples from different individuals.

Immunoglobulin subclass profiles of anti-idiotypic antibodies to GAD65Ab differ between type 1 diabetes patients and healthy individuals

Previously we reported the presence of anti-idiotypic antibodies (anti-Id)-specific to autoantibodies against GAD65 (GAD65Ab) in healthy individuals while the activity of anti-Id directed to GAD65Ab in type 1 diabetes (T1D) patients was significantly lower. These anti-Id recognize the antigen-binding site of GAD65Ab, thus preventing their binding to GAD65. Here, we characterized the IgG subclass profile of these anti-Id (GAD65Ab specific) and of the associated GAD65Ab themselves. The IgG subclass response of anti-Id in healthy individuals (n = 16) was IgG3-dominated, while in T1D patients (n = 8) IgG1 was the major IgG subclass. The GAD65Ab bound by anti-Id in both healthy individuals (n = 38) and GAD65Ab-negative T1D patients (n = 35) showed a predominant rank order of IgG1 > IgG2 > IgG4 > IgG3. However, the frequency of GAD65Ab of the IgG4 subclass was significantly higher in T1D patients (P < 0.05). We conclude that the IgG subclass profile of anti-Id (GAD65Ab specific) in healthy individuals differs from that in T1D patients. These differences may provide insights into the development of these antibodies.

In vivo enzymatic modulation of IgG glycosylation inhibits autoimmune disease in an IgG subclass-dependent manner

IgG antibodies are potent inducers of proinflammatory responses. During autoimmune diseases such as arthritis and systemic lupus erythematosus, IgG autoantibodies are responsible for the chronic inflammation and destruction of healthy tissues by cross-linking Fc receptors on innate immune effector cells. The sugar moiety attached to the asparagine-297 residue in the constant domain of the antibody is critical for the overall structure and function of the molecule. Removal of this sugar domain leads to the loss of the proinflammatory activity, suggesting that in vivo modulation of antibody glycosylation might be a strategy to interfere with autoimmune processes. In this work, we investigated whether removal of the majority of the IgG-associated sugar domain by endoglycosidase S (EndoS) from Streptococcus pyogenes is able to interfere with autoimmune inflammation. We demonstrate that EndoS injection efficiently removes the IgG-associated sugar domain in vivo and interferes with autoantibody-mediated proinflammatory processes in a variety of autoimmune models. Importantly, however, we observed a differential impact of EndoS-mediated sugar side chain hydrolysis on IgG activity depending on the individual IgG subclass.

T cell reactivity against the SmD1(83-119) C terminal peptide in patients with systemic lupus erythematosus

BACKGROUND

The SmD1(83-119) peptide is a major target of the B cell response in patients with systemic lupus erythematosus (SLE).

OBJECTIVE

To investigate the T cell response directed against this peptide, its disease specificity, and possible impact on SLE pathogenesis.

METHODS

Peripheral blood mononuclear cells derived from 28 patients with SLE and 29 healthy and disease controls were stimulated by the SmD1(83-119) and the recombinant (r)SmD1 protein, and [3H]thymidine incorporation was measured. Patients with SLE were simultaneously tested for autoantibodies, disease activity, clinical symptoms, and medical treatments.

RESULTS

T cell reactivity against the SmD1(83-119) peptide was detected in 11/28 (39%) patients with SLE and against the rSmD1 protein in 10/28 (36%) patients. In contrast, only 2/29 (7%) controls exhibited SmD1 reactivity. An analysis of proliferation kinetics showed that SmD1 reactive T cells are activated in vivo, as additionally confirmed by cytometric analysis. Addition of mammalian dsDNA to rSmD1 enhanced the rSmD1-specific T cell response. SmD1(83-119)-specific T cell reactivity was significantly more common in patients with cardiac and pulmonary symptoms. No correlation between T and B cell responses and disease activity was seen.

CONCLUSION

SmD1(83-119) is a major T cell epitope of SmD1, commonly recognised by T cells from patients with SLE and much less commonly found by healthy or disease controls. This strong T cell reactivity as well as the high frequency and specificity of anti-SmD1(83-119) antibodies in SLE suggest a possible role in SLE pathogenesis, at least in a subset of patients.

Autoreactive T cells in murine lupus: origins and roles in autoantibody production

The conventional paradigm to explain systemic lupus erythematosus (SLE) is that disease results from tissue deposition of pathogenic autoantibodies and immune complexes, secondary to activation of autoreactive B cells in the context of help from alphabeta T cells. Recent work in murine lupus has confirmed this notion and demonstrated that autoantigen-specific alphabeta T cells are absolutely required for full penetrance of disease, with such autoreactive alphabeta T cells, even in Fas-intact mice, likely arising from defects in peripheral tolerance. These studies have also revealed a network of regulation that also involves nonclassical pathogenic and downregulatory alphabeta and gammadelta T cells, suggesting that the lupus immune system involves more complex interactions than the conventional paradigm suggests.

T cells in murine lupus: propagation and regulation of disease

MRL/Mp-lpr/lpr mice develop a spontaneous lupus syndrome, including hypergammaglobulinemia, autoantibodies, glomerulonephritis, and lymphadenopathy. To investigate the role of lymphocytes subsets in the pathogenesis of disease, lupus-prone MRL mice deficient in alpha beta T cells, gamma delta T cells, or both were generated. Mice deficient in alpha beta T cells developed a partially penetrant lupus syndrome, characterized by lymphadenopathy, elevated levels of class-switched immunoglobulins, an increased incidence of antinuclear antibodies, and immune deposits in kidneys which progressed to renal insufficiency over time. In comparison to wild type animals, gamma delta T cell-deficient animals developed an accelerated and exacerbated disease phenotype, characterized by accelerated hypergammaglobulinemia and enhanced autoantibody production and mortality. Repertoire analysis of these latter animals identified polyclonal expansion (V beta) of alpha beta CD4+ B220-cells. Mice lacking both alpha beta and gamma delta T cells failed to generate class-switched autoantibodies and immune complex renal disease. First, these findings demonstrate that murine lupus in the setting of Fas-deficiency does not absolutely require the presence of alpha beta T cells, and they also suggest that a significant basis for MRL/lpr disease, including renal disease, involves alpha beta T cell-independent, gamma delta T cell dependent, polyreactive B cell autoimmunity, upon which alpha beta T cell-dependent mechanisms aggravate specific autoimmune responses. Second, these data indicate that gamma delta T cells partake in the regulation of systemic autoimmunity, presumably via their effects on alpha beta CD4+ B220-T cells that provide B cell help. Finally, these results demonstrate that MRL/lpr B cells, despite their intrinsic abnormalities, cannot per se cause tissue injury without T cell help.

Restricted heterogeneity and changing spectrotypes in autoantibodies to La/SS-B

Isoelectric focusing (IEF) spectrotype of specific immunoglobulins has been studied as a marker for B-cell clonality. In the present study, the spectrotype of anti-La antibodies in human autoimmune sera were analyzed by newly developed IEF sandwich assay in which focused total immunoglobulin on filter papers are incubated with crude antigen followed by horse-radish peroxidase-labeled anti-La antibodies. The anti-La spectrotypes contained oligoclonal bands, the positions and patterns of which are different in each patient, suggesting the preferential expansion of limited numbers of anti-La producing B-cell clones unique to individual patients. Furthermore, the bands on anti-La spectrotype in sequentially obtained sera changed continuously, suggesting alteration in the expanding anti-La producing clones. These may reflect affinity maturation and/or diversification of the B-cell epitopes involving somatic mutation.

Differential antibody isotype reactivity to specific antigens in human lymphatic filariasis: gp15/400 preferentially induces immunoglobulin E (IgE), IgG4, and IgG2

Lymphatic filarial infection in humans is associated with a strong skewing of the immune response towards the TH2 arm, with prominent interleukin 4-producing cells and elevated levels of immunoglobulin G4 (IgG4) and IgE antibodies in peripheral blood. To determine how such a generalized TH2 imbalance governs responses to individual parasite antigens, the profiles of isotypes of antibodies to two recombinant proteins of Brugia spp. were studied. One molecule was the C-terminal portion of the filarial heat shock protein 70 (Bpa-26), representative of a cytoplasmic protein, and the second antigen was a single unit of the tandem repeats of a Brugia polypeptide (BpL-4), a secreted product which is prominently exposed to the immune system. Serum samples from 146 individuals resident in areas in which brugian filariasis is endemic were used, and it was found that whereas the levels of IgG1 and IgG3 responses to both Bpa-26 and BpL-4 were high, IgG4 and IgE antibodies to only BpL-4, not to Bpa-26, were prominent. Thus, an antigen which is chronically exposed to the immune system elicited a TH2-dependent isotype switch, as manifested by increased IgG4 and IgE responses. Moreover, IgG4 and IgE responses to BpL-4 showed a strong negative association, suggesting that mediators other than interleukin 4 must be responsible for such differential regulation of these two isotypes. When the data were analyzed as a function of clinical status, a striking association between elevated levels of IgG3 antibodies to Bpa-26 and manifestation of chronic obstructive disease was found; elephantiasis patients showed significantly higher levels of IgG3 antibodies to Bpa-26 than microfilaremics and asymptomatic amicrofilaremics. This indicates that an imbalance of isotypes of antibodies to particular filarial antigens might play a role in the pathogenesis of chronic disease.

Altered immunoglobulin concentrations and light chain ratios in juvenile onset mixed connective tissue disease

Immunological disturbances may result in altered immunoglobulin concentrations and kappa/lambda light chain (kappa/lambda) ratios. We measured the kappa/lambda ratios of total serum immunoglobulins and of polyclonal IgG, A, and M separately as well as concentrations of these immunoglobulins in fourteen patients with juvenile onset mixed connective tissue disease. When comparing the patient group with a reference group the mean serum IgG and IgA concentrations were respectively 2.98 G/L (p = 0.0012) and 0.79 G/L (p = 0.0114) higher in the group of patients with juvenile onset mixed connective tissue disease. The mean IgM concentration was 0.39 G/L (p = 0.0002) lower. The mean kappa/lambda ratios of total serum immunoglobulins, serum IgG, and serum IgA were respectively 0.20 (p = 0.0226), 0.28 (p = 0.0016) and 0.10 (p = 0.0732), higher in the group of patients with mixed connective tissue disease as compared with the reference group. Mean serum IgM kappa/lambda ratio, however, was 0.21 (p = 0.0046) lower. The alterations of the serum immunoglobulin concentrations and of the kappa/lambda ratios reflect immunological disturbances in patients with juvenile onset mixed connective tissue disease. The increased concentration of serum IgG and raised IgG kappa/lambda ratio and decreased concentration of serum IgM with decreased IgM kappa/lambda ratio indicate that the synthesis of kappa-bearing immunoglobulins mainly is affected.

Isotypic distribution of anti-pyruvate dehydrogenase antibodies in patients with primary biliary cirrhosis and their family members

IgG subclasses of anti-pyruvate dehydrogenase (PDH) antibodies were determined in 72 patients with primary biliary cirrhosis. All isotypes were detected, but IgG3, IgG1, and IgG2 predominated independently or in association. An average of 33.3 +/- 19.1% of the anti-PDH IgG was IgG1 (mean optical density, 0.863 +/- 0.783, vs 0.053 +/- 0.038 in the normal controls), 25.0 +/- 17.8 IgG2 (0.652 +/- 0.656 vs 0.062 +/- 0.030), 39.5 +/- 23.4% IgG3 (1.140 +/- 0.917 vs 0.010 +/- 0.023), and 2.4 +/- 7.4% IgG4 (0.060 +/- 0.182 vs 0.012 +/- 0.007). Anti-PDH IgG were restricted to IgG1 in the family members of patients (0.180 +/- 0.403).

Comparative analysis of the antibody response to the HTLV-I gag and env proteins in HTLV-I asymptomatic carriers and HAM/TSP patients: an isotype and subclass analysis

We have compared the immunoglobulin isotype and IgG subclass and the titre of neutralizing antibody responses to the human T cell lymphotropic virus type I (HTLV-I) between a group of asymptomatic HTLV-I infected individuals and a group with the neurological disease HTLV-I associated myelopathy/tropical spastic paraparesis (HAM/TSP). A western blot titration assay and an envelope peptide ELISA were used to determine the presence and titre of isotype and IgG subclass responses to the gag p19 and p24 proteins and to the envelope protein. Significant increases were observed in the number of individuals seropositive for a particular isotype and IgG subclass in the HAM/TSP group versus the asymptomatic group particularly for IgM and IgE and to a lesser extent, IgA. The predominant IgG subclasses to the HTLV-I p19, p24 and envelope proteins were IgG1 and IgG3. This finding was also observed in the titres of the antibody responses to these HTLV-I proteins. The HAM/TSP group also exhibited significantly higher neutralizing antibody titres than the asymptomatic group. This evidence suggests that some form of chronic immune stimulation might be involved in the immunopathogenesis of HAM/TSP. In addition, by following the Western blot titre to the IgM and IgE isotypes in particular, it may be possible to identify asymptomatic individuals progressing to HAM/TSP.

B cell activation in clinically quiescent systemic lupus erythematosus (SLE) is related to immunoglobulin levels, but not to levels of anti-dsDNA, nor to concurrent T cell activation

In clinically quiescent SLE hypergammaglobulinaemia, presence of autoantibodies, and increased soluble IL-2 receptors (sIL-2R) have been reported, suggesting persistent B as well as T cell activation. In contrast, the primary immune response to test antigens is markedly decreased. To analyse these phenomena at a cellular level, we undertook a cross-sectional study on 13 non-active SLE patients and 15 controls. We determined the composition of lymphocyte subsets with special attention to activation markers (CD25, HLA-DR, CD38) and the presence of naive T cells (CD45RO-), and related those findings to serological parameters. In non-active SLE patients the expression of activation markers on B cells and T cells was higher than in normal controls (P < or = 0.02), but was not interrelated. Percentages of activated B cells in SLE were related to levels of total IgG (P < 0.02) and IgM (P < 0.02) but not to anti-dsDNA, suggesting a disordered immune system also in clinically quiescent SLE. Numbers of CD4+ cells (P < 0.001) and CD4+CD45RO- cells (P < 0.05) were decreased. The latter finding might explain the anergy to primary test antigens in clinically quiescent SLE.

T- and B-cell abnormalities in systemic lupus

A wealth of T- and B-cell abnormalities has been described in systemic lupus erythematosus (SLE). In general, T and B cells manifest evidence of intense in vivo activation, yet perform poorly when tested for in vitro responsiveness to exogenous antigen. The immune system behaves as if its commitment to self-responsiveness overrides the normal capacity to respond to immunogenic challenges. Many immunoregulatory abnormalities have been characterized, but their relation to disease remains controversial. Although a widely accepted unifying hypothesis for the vigorous autoantibody production and associated immune deficiency of SLE is lacking, it seems certain that the profound abnormalities of T and B cells in SLE are intertwined with the fundamental cause of this illness.

More evidence of distinctive features of mixed connective tissue disease

A comparison of clinical, immunological and HLA-D region antigen features was made between 22 patients with mixed connective tissue disease (MCTD) and 118 patients with systemic lupus erythematosus (SLE), scleroderma or primary Sjögren's syndrome. The MCTD patients had hypergammaglobulinemia more often than did those with SLE and scleroderma, but had less skin ulceration, serositis, nephritis, central nervous system disease and hypocomplementemia than the SLE patients. The frequencies of HLA-DR4 and its Dw4 subtype were significantly increased in MCTD as compared with both the other patient groups and healthy controls. Anti-RNP antibodies and the clinical characteristics together seem to illustrate a disease syndrome which is clinically and genetically distinct and fits with the prevailing concept of MCTD.

IgG subclasses in systemic lupus erythematosus and other autoimmune rheumatic diseases

In this study the concentration of the different subclasses of IgG in sera from patients with a range of autoimmune rheumatic diseases (ARD) was detected by radial immunodiffusion. In the second part the IgG subclasses of autoantibodies that recognize single-stranded DNA (ssDNA), double-stranded DNA (dsDNA), Ro, La, Sm and RNP in patients with ARD were measured by enzyme-linked immunosorbent assay. We studied 15 patients with lupus, 20 patients each with primary and secondary Sjögren's syndrome (SS) and 10 each with rheumatoid arthritis (RA), scleroderma and myositis. Twenty healthy controls were also measured. The serum concentration of IgG2 in ARD patients was generally reduced. In contrast, the concentrations of IgG1, IgG3 and IgG4 subclasses were normal or raised. A high degree of correspondence in the IgG1, IgG2 and IgG3 responses to dsDNA and ssDNA in SLE was found. Notable differences in the IgG1 anti-Ro and ssDNA responses compared to the other subclasses were seen in 1 degree and 2 degrees SS. In addition, an unexpected high level of IgG4 antibodies to ssDNA in 1 degree SS (65%) and IgG4 antibodies to Sm/RNP in RA was observed.

Immunoglobulin class and IgG subclass distribution of anticardiolipin antibodies in patients with systemic lupus erythematosus and associated disorders

The class and subclass distribution of an antibody response may give insight into the stimulating mechanism and likely effector functions. IgA, IgG and IgM anticardiolipin antibodies (aCL) were quantified in a consecutive series of 200 samples sent to an autoimmune serology laboratory to determine the relationships between aCL responses of each of these antibody classes and, in particular, whether there was any utility in the measurement of IgA aCL. Positive results for one of the three aCL isotypes were found in 105 samples (53%), and in 41 samples IgA aCL was detected (21%). However, amongst these unselected samples, little additional information was obtained by measurement of IgA aCL, which was found in conjunction with IgM or IgG aCL in all but five samples, and in these the isolated elevation of IgA aCL was only slight, and showed no disease specificity. The levels of each of the four IgG subclasses of aCL were measured in a subgroup of serum samples from 28 patients with autoimmune disease and from 29 patients with syphilis. Amongst the SLE patients IgG1 and IgG3 aCL were the predominant IgG subclasses, consistent with an antigen-driven, T cell-dependent antibody response. However, a subgroup of eight of the autoimmune subjects had predominant elevation of IgG2 aCL, possibly implying a role for T cell-independent antibody production to cardiolipin. Amongst the syphilis patients IgG1 and IgG3 aCL were also the predominant subclasses of aCL but IgG4 aCL were also detected in the majority of subjects, consistent with prolonged antigenic stimulation.

Cross-reactivity of the subunit of the Sm ribonucleoprotein autoantigen with proline-rich polypeptides

Using recombinant fusion proteins representing different regions of the human Sm B/B' polypeptide, the 4B4 monoclonal anti-Sm antibody was found to bind a C-terminus epitope that is proline-rich. 4B4 cross-reacted with the p24 gag protein of HIV-1 and with other polypeptides rich in proline residues, including collagen. BALB/c mice immunized with human collagen not only produced antibodies to the immunizing antigen but also antibodies to Sm. This immune mouse serum also recognized C-terminus B/B' fusion proteins. These data suggest that the Sm B/B' antigen contains a poly-Pro epitope that is shared by several autoantigens and retroviral proteins. These sites may be important in the induction of autoantibodies through molecular mimicry.

Patterns of heavy and light chain utilization in the antibody response to single-stranded bacterial DNA in normal human subjects and patients with systemic lupus erythematosus

Although anti-DNA antibodies are generally considered to be specific markers for systemic lupus erythematosus (SLE), antibodies binding DNA from certain bacterial species can be found in the sera of normal subjects. To characterize the immunochemical properties of these antibodies, the IgG subclass and light chain profile of antibodies to single-stranded micrococcal DNA (MC DNA) in the sera of normal subjects and patients with SLE was determined. The anti-MC DNA response in normal sera was predominantly of the IgG2 subclass with a marked predominance of kappa light chains. In contrast, anti-MC DNA antibodies in SLE sera exhibited all IgG subclasses with a predominance of the IgG1 subclass and both kappa and lambda light chains were represented. These results suggest that antibodies to bacterial DNA in the sera of normal subjects and patients with SLE differ in patterns of immunoglobulin gene expression; the restricted response of normal subjects may be related to the binding to a discrete DNA determinant.

Clinical significance of IgG subclasses of Anti-Sm and U1 ribonucleoprotein antibodies in patients with systemic lupus erythematosus and mixed connective tissue disease

IgG subclasses of anti-Sm and anti-U1 ribonucleoprotein (U1 RNP) antibodies were determined using a new clone of the anti-IgG2 antibody (HG2-56F). Although the predominance of IgG1 coincided with previous reports, IgG2 anti-Sm and U1 RNP antibodies were detected in numerous patients. IgG3 anti-Sm antibody significantly correlates with joint involvement and a high titer of anti-DNA antibody. On the other hand, IgG4 anti-U1 RNP antibody significantly correlated with esophageal dilation and muscular involvement. These results may suggest that some IgG subclasses are related to a specific clinical feature or manifestation.

Laboratory diagnosis of HIV infection

Laboratory diagnosis of human immunodeficiency virus (HIV) infection is complicated by absence of data on sensitivity, specificity and predictive value of the various tests as they apply to children. The presence of maternal anti-HIV passively transmitted across the placenta also confounds diagnosis. The authors review currently available data on the detection of HIV, HIV genome, and HIV gene products, as well as the diagnostic value of detecting serologic and cellular responses to HIV in infants and children.

The role of an autoantigen, histidyl-tRNA synthetase, in the induction and maintenance of autoimmunity

Patients with systemic autoimmune diseases make specific autoantibodies that are directed against self structures. According to one view, these autoantibodies arise as a result of an immune response to foreign antigens such as infectious agents that share, by molecular mimicry, common structures with host proteins. An alternative view is that the target autoantigen itself initiates, selects, and sustains autoantibody synthesis. We show here that anti-Jo-1 autoantibodies directed against histidyl-tRNA synthetase in the human autoimmune muscle disease polymyositis undergo, in addition to spectrotype broadening and class switching, the sine qua non of an immune response to the target antigen--affinity maturation to that antigen. We demonstrate further that these autoantibodies, unlike anti-synthetase antibodies induced in mice immunized with heterologous antigen, bind only nonlinear epitopes on the native human synthetase that remain exposed when the enzyme is complexed to tRNA(His). These data suggest that the native target autoantigen itself has played a direct role in selecting and sustaining the autoantibody response and sharply restrict the time and the way in which a molecular mimic might act to provoke autoantibodies.

IgG subclasses in the serum and skin in subacute cutaneous lupus erythematosus and neonatal lupus erythematosus

IgG subclasses differ in their biologic and chemical properties, such as complement fixation, protein and cellular binding, and placental transfer. In this study, IgG subclasses of anti-Ro/SSA antibodies in subacute cutaneous lupus (SCLE) and neonatal lupus (NLE) are examined in the serum and in the skin. IgG subclasses in NLE beginning in utero (NLE-heart disease) are compared to subclasses in NLE beginning after birth (NLE-skin disease). Human skin was grafted onto athymic mice, mice were injected with one of eight anti-Ro/SSA maternal NLE sera (four heart block, four skin disease) or seven anti-Ro/SSA SCLE sera, and grafts were examined for IgG subclasses using monoclonal anti-human IgG subclass reagents in an immunofluorescent technique. Lesional skin was examined from four SCLE patients. IgG1 was the only IgG subclass detected in the grafts and skin lesions. IgG1 was the predominant anti-Ro/SSA IgG subclass detected in SCLE and NLE sera in an ELISA using a synthetic Ro/SSA polypeptide. These studies show that the maternal anti-Ro/SSA autoantibodies in NLE-heart disease sera are predominantly IgG1 and are therefore likely to be present in the fetus at the time of gestation, when heart block usually develops. Second, differences in the clinical presentations of NLE (in utero vs. postnatal disease) cannot be attributed to differences in anti-Ro/SSA IgG subclasses. Finally, the subclass bound in the skin in SCLE is IgG1, a subclass capable of mediating tissue injury via complement or cellular effectors.

Heavy and light chain utilization in autoantibodies of elderly patients with systemic lupus erythematosus

To determine whether age-related changes in immune function affect patterns of autoantibody production, we have examined the isotype and light chain utilization in autoantibodies of elderly patients with systemic lupus erythematosus (SLE). Enzyme-linked immunosorbent assays (ELISA) were used to determine the frequencies of IgG and IgM antibodies to single-stranded DNA (ssDNA), Sm, and the 70K protein component of RNP in the sera of 53 patients with SLE older than age 60. The IgG subclass distributions and kappa/lambda ratios for each of these autoantibodies were also determined and compared to measurements performed on the sera of 53 young adult patients with SLE. The frequencies of autoantibodies of each specificity, except IgM anti-ss DNA antibodies, were higher among the young adult patients, although the magnitudes of the responses were similar in both age groups. IgG anti-Sm antibodies were composed of both IgG1 and IgG2 subclasses, while IgG anti-70K RNP and IgG anti-ssDNA were predominantly of the IgG1 subclass. There were no differences in the IgG subclass distributions of any of the three autoantibodies between the elderly and young adult patient sera. The kappa/lambda ratios for each of the three autoantibodies were similar to that present in total serum immunoglobulins, and kappa/lambda ratios of autoantibodies, standardized to the kappa/lambda ratios of serum, were not different between elderly and young adult groups. Few patient sera of either age group (9 elderly, 7 young adult) demonstrated even midly skewed light chain ratios in their autoantibody responses. Thus, despite developing in an immunological environment that may have altered the clonality and isotype distribution of their responses, the autoantibodies produced by elderly patients with SLE were qualitatively similar to autoantibodies of younger patients.

Use of molecular cloning methods to map the distribution of epitopes on topoisomerase I (Scl-70) recognized by sera of scleroderma patients

We report the initial molecular characterization of the autoimmune response against DNA topoisomerase I (topo I; Scl-70). Sera from 36 patients with scleroderma and 4 healthy control subjects were studied using 6 subcloned portions of topo I. Twenty-three sera recognized at least 2 independent epitopes on the molecule. Therefore, anti-topo I, like other non-organ-specific autoantibodies characterized to date, is polyclonal and multifocal. The cloned protein should prove suitable for sensitive early detection of anti-topo I in the clinical setting.

Antiphospholipid antibody syndrome: immunologic and clinical aspects

Antiphospholipid antibody is associated with a clinical syndrome of vascular thrombosis, thrombocytopenia, recurrent fetal loss, and livedo reticularis, whether or not a clinical diagnosis of systemic lupus erythematosus (SLE) coexists. A positive antiphospholipid antibody test is defined by enzyme-linked immunosorbent assay (ELISA) (antiphospholipid antibody itself) or by coagulation assay (lupus anticoagulant). These are similar but not identical antibodies. The test for syphilis is less closely related to the preceding two and is less regularly associated with clinical complications. The mechanism of action of either antiphospholipid antibody or lupus anticoagulant is as yet unknown. SLE-induced but not infection-induced antiphospholipid antibody has immunoglobulin G2 (IgG2) and IgG4 predominance. It recognizes all negatively charged phospholipids, but various physical characteristics of the phospholipids alter the recognition patterns. Treatment for the antiphospholipid antibody syndrome has not been clearly defined. Anticoagulation with aspirin, heparin, or warfarin is currently favored. A role for corticosteroid remains to be demonstrated.

Recognition of synthetic peptides of Sm-D autoantigen by lupus sera

The reactivity of autoantibodies present in the serum of patients with systemic lupus erythematosus (SLE) was investigated by ELISA using seven overlapping synthetic peptides representing the entire sequence of the polypeptide D component of 'Sm antigen'. Of the 165 SLE sera tested, 59% were found to contain IgG antibodies able to bind to peptide 1-20, while 37% of the sera reacted with peptide 44-67. All sera reacting with peptide 44-67 also reacted with peptide 1-20. These two peptides were only seldom recognized by the sera of 187 patients with other rheumatic autoimmune diseases or by 53 sera of normal individuals. In a parallel study using sera that reacted with the D band in immunoblotting, most of the sera recognized peptides 44-67 (89%) and 1-20 (67%), while 33% of them reacted with peptide 97-119. The use of these synthetic peptides in ELISA may be of considerable help for detecting anti Sm autoantibodies.

Immunoglobulin class and subclass restriction of autoimmune responses in secondary syphilis

The immunoglobulin (Ig) class and IgG subclasses of autoantibodies to commercial VDRL antigen, creatine kinase (CK), and fibronectin (Fn) in the sera of patients with various stages of syphilis were quantified using solid-phase radioimmunoassays (RIA) and ELISA. Sera from patients with active secondary syphilis, initially positive for anti-Fn and anti-CK autoantibodies by RIA, were re-evaluated by ELISA using monoclonal antibodies (MoAb) for detection of human Ig class and subclass responses. Results of these assays revealed that anti-Fn and anti-CK responses were not only IgG in nature, but dramatically skewed to IgG1 and IgG3 subclasses. While the restricted, co-expression of these isotypes seemingly paralleled anti-treponemal activity, inverse relationships actually existed between the subclass responses to Fn and those to Treponema pallidum. In contrast, anti-VDRL were predominantly IgM in 17 of 22 patients. Of those sera exhibiting detectable anti-VDRL IgG activity, responses appeared to be restricted to IgG1. These results suggest that different control mechanisms may be responsible for regulation of the various autoantibody responses expressed during syphilitic infection.

Expression of IgM and IgG autoantibodies in pediatric and adult systemic lupus erythematosus

To compare patterns of autoantibody responses in pediatric and adult patients with systemic lupus erythematosus (SLE). IgG and IgM antibodies to single-stranded DNA (ssDNA), Sm, and the 70-kDa protein component of the RNP antigen (70-kDa RNP) were measured in 29 pediatric and 36 adult patients by enzyme-linked immunosorbent assays. Antibodies of either isotype to ssDNA, Sm, and 70-kDa RNP were present in 64, 58, and 79% of pediatric patients, respectively, comparable to prevalences of these autoantibodies in the adult SLE patients. Pediatric SLE patients were more likely than adult patients to have IgM anti-Sm antibodies (41.4% vs 13.9%, P = 0.02) and tended to more commonly express IgM anti-70-kDa RNP and IgM anti-ssDNA antibodies. The prominence of IgM autoantibody responses among pediatric SLE patients was shown by multiple logistic regression analysis to be related to total IgM concentrations and not related to age or duration of disease. Sequential serum samples available from several pediatric patients revealed the maintenance of similar patterns of isotype responses over time in approximately one-half of patients. In those patients whose responses changed over time, the variations in isotype expression were consistent with maturation of antibody responses of each specificity. While these results demonstrate similarities in autoimmune reactivities between pediatric and adult SLE patients, the serologic study of pediatric patients may provide an opportunity to more readily investigate the evolution of autoantibody responses.

Comparison of IgG subclass autoantibodies in patients with systemic lupus erythematosus and subacute cutaneous lupus erythematosus

Circulating antinuclear antibodies and in vivo bound immunoglobulins at the dermal-epidermal junction are frequently seen in patients with lupus erythematosus. The present study was designed to examine the distribution of the IgG subclasses of in vivo skin bound IgG and circulating antinuclear antibodies (ANA) in patients with systemic lupus erythematosus (SLE) or subacute cutaneous lupus erythematosus (SCLE). Immunofluorescence studies on skin biopsies showed IgG1 to be the predominant IgG subclass in SCLE patients, present in 20 of 21 (95%) of the specimens. IgG2 was present in 4 patients (19%), IgG3 in 1 (5%), and IgG4 in 7 (33%). The frequencies of IgG2, IgG3, and IgG4 skin staining were significantly higher in the seven SLE patients who were studied: IgG1 in 7/7 (100%), IgG2 in 7/7 (100%) and IgG4 in 6/7 (86%). Immunoblot analysis for the IgG subclasses was performed on serum of 29 patients with SCLE who had antibodies to SSA/Ro antigen. Twenty-seven (93%) of these patients were positive for IgG1 anti-SSA/Ro antibody, while the frequencies for IgG2, IgG3, and IgG4 anti-SSA/Ro were very low. These studies indicate that there is a difference in the IgG subclass antibody response in patients with SLE and SCLE. The presence of more than one subclass antibody may be indicative of systemic disease.

Antireticulin antibody in systemic sclerosis

The prevalence, immunoglobulin class, and IgG subclass of antireticulin antibody in the serum samples of 32 patients with systemic sclerosis were investigated by indirect immunofluorescence on unfixed rodent tissue. Antireticulin antibody was present in 22/32 (69%) of patients and belonged to the IgG class in 19/22 (86%), the IgA class in 13/22 (59%), and the IgM class in 6/22 (27%) of positive sera. IgG1 was the predominant subclass of IgG antireticulin antibody, occurring either alone or in association with IgG3 in 12/19 cases (63%). Thus antireticulin antibody of the IgG and IgA classes is found in most patients with systemic sclerosis. The finding of an autoantibody with reactivity for collagen-like fibres in systemic sclerosis indicates that the antibody has a potential role in the pathogenesis of the disease, and as it belongs to the IgA class this suggests that it arises in response to antigens presented to the immune system at the mucosal level.

Immunoglobulin classes in biopsies of autoimmune liver disease

The immunological isotypes of plasma cell infiltrates in a series of consecutive liver biopsies from patients with chronic active hepatitis (CAH) and primary biliary cirrhosis (PBC) were determined immunohistochemically. The plasma cell infiltrate was more pronounced in PBC than in CAH. IgA and IgG isotypes predominated in CAH, and IgM and IgG in PBC. The expected predominance of kappa light chains was observed in every biopsy in PBC. However, in 8/14 CAH biopsies the plasma cells were predominantly lambda isotype. Lambda predominance was significantly associated with the presence of serum autoantibodies. These findings would suggest that different mechanisms operate in the pathogenesis of these two autoimmune liver diseases.

Origin and regulation of a disease-specific autoantibody response. Antigenic epitopes, spectrotype stability, and isotype restriction of anti-Jo-1 autoantibodies

Anti-Jo-1 antibodies (AJoA), which bind to and inhibit the activity of histidyl-transfer RNA synthetase (HRS), are found in a genetically and clinically distinct subset of myositis patients. This specificity suggests that understanding the antigenic epitopes and immunoregulation governing the production of AJoA may result in clues to disease pathogenesis. Limited digestion of human HRS by V8 protease resulted in four major antigenic polypeptides of 35, 34, 21, and 20 kD; digestion with subtilisin gave four fragments of the same sizes and two additional major antigenic polypeptides of 28 and 17 kD. Sera from 12 AJoA positive patients reacted indistinguishably with these proteolytic fragments by Western blotting, and AJoA elution studies suggested a common epitope(s) on all six. Isoelectric focusing showed a different polyclonal pattern of AJoA in each patient, although serial analyses in individual patients revealed stable AJoA spectrotypes over years of observation. Enzyme-linked immunosorbent assays showed that the AJoA response was mainly restricted to the IgG1 heavy chain isotype. The levels of IgG1 AJoA varied in proportion to disease activity over time but were independent of total IgG1 levels, and three patients became AJoA negative as their myositis remitted after treatment. These findings suggest that AJoA are induced by an antigen-driven mechanism, bind to a common epitope or epitopes on HRS, and are modulated by an immune response closely linked to that which is responsible for myositis in these patients.

IgG1 and IgG2 are the predominant subclasses of antiphospholipid antibody in women with the lupus anticoagulant

We studied the sera of 36 patients with lupus anticoagulant and IgG antibodies against both phosphatidylserine and cardiolipin. Most sera also had IgG antibodies against other phospholipids: 97% against phosphatidylinositol, 91% against phosphatidylglycerol, and 82% against phosphatidylethanolamine. IgG2 was the predominant subclass against cardiolipin and phosphatidylserine; 35 of 36 patients (98%) had IgG2 against both phospholipids. Most patients also had the IgG1 subclass; 32 of 36 (89%) against cardiolipin and 25 of 36 (69%) against phosphatidylserine. IgG3 and IgG4 subclasses were present at very low concentrations and in only a minority of the sera. The antibody response against phosphatidylserine was characterized by significantly less IgG1 than was the response against cardiolipin (P less than 0.01), although the IgG2 responses against each phospholipid were not different. IgG subclasses were unrelated to any other aspect of the patients' history, including a history of thrombocytopenia or thrombosis, a positive antinuclear antibody test, or a diagnosis of systemic lupus erythematosus.

Regulation of the anti-Sm autoantibody response in systemic lupus erythematosus mice by monoclonal anti-Sm antibodies

The administration of certain monoclonal anti-Sm antibodies (2G7, 7.13) induced most MRL/lpr mice to become anti-Sm positive by 5 mo of age, although other anti-Sm monoclonals (Y2, Y12) suppressed the spontaneous response. Positive anti-Sm antibody enhancement occurred efficiently only in MRL/lpr mice and not in other systemic lupus erythematosus mice that have little spontaneous anti-Sm production. The enhancement by anti-Sm antibodies was specific for the anti-Sm response. The mechanism of the passive antibody enhancement was apparently not isotype- or idiotype-related. The fine specificity of the anti-Sm monoclonal antibody may be essential to its enhancing or suppressing effects, since both enhancing monoclonals recognized only the D Sm polypeptide, whereas both suppressing monoclonals saw the D and the B polypeptides. Furthermore, analysis of serial bleeds from unmanipulated MRL mice that developed anti-Sm positivity showed that the D specificity almost always appeared first. We hypothesize, therefore, that those animals in which an anti-Sm response is initiated by D-specific B-cell clones can become serologically positive with the aid of a positive feedback loop. In contrast, animals in which the initial specificity is for both B and D peptides would be prevented from developing a full anti-Sm response.

IgG subclasses of antibodies to the collagen-like region of C1q in patients with systemic lupus erythematosus

Low molecular weight C1q-binding IgG in the sera of patients with systemic lupus erythematosus consists of autoantibodies to the collagen-like region of C1q. In this study, the IgG subclass distribution of these autoantibodies was examined by radial immunodiffusion with polyclonal antibodies specific for each subclass. The purified antibodies to the collagen-like region of C1q possessed the IgG subclass distribution present in normal serum.

Isotype analysis of the anti-CENP-B anticentromere autoantibody: evidence for restricted clonality

Utilizing the centromere B fusion protein (CENP-B) and specific, matched monoclonal antiisotype reagents in an enzyme-linked immunosorbent assay, we found that anti-CENP-B autoantibodies were skewed to the IgG1 isotype. The overall kappa:lambda light chain ratio was 2:1, although several individual sera showed a strong predominance of one of the light chains. Isoelectric focusing of light chain-skewed sera showed polyclonal patterns. Our findings are consistent with the anti-CENP-B autoantibody response being a chronic, antigen-driven response.

The B-cell activation pathway in human systemic lupus erythematosus: imbalanced in vitro production of lymphokines and association with serum analytical findings

Recent knowledge of B-lymphocyte physiology has clarified the role of T cell-derived lymphokines in clonal proliferation and differentiation of B-cell responses. Lymphokine production was analyzed in 19 systemic lupus erythematosus (SLE) patients and sex- and age-matched controls in relation to clinical activity and steroid treatment. When in vitro production of interleukin-2 (IL-2) and B-cell growth factor (BCGF) was tested, both activities were found to be diminished in the group of patients (P less than 0.01), while B-cell differentiation factor (BCDF) activity was higher in this group with respect to normal controls (P less than 0.01). Interestingly enough, this in vitro BCDF synthesis was positively correlated with clinical activity regardless of low-dose steroid treatment. A correlation was also found between BCDF production and the levels of IgG (r = 0.64, P less than 0.01), anti-DNA antibodies (r = 0.52, P less than 0.05), and the IgG/IgM ratio (r = 0.7, P less than 0.01) in serum. Implications of these abnormal T-lymphocyte functions in SLE with respect to in vivo B-cell function are discussed.

An IgG subclass imbalance in connective tissue disease

A group of 16 patients with a disproportionate polyclonal increase in their serum IgG1, resulting in raised concentrations of total IgG immunoglobulin, has been discovered. The other IgG subclasses in these patients are either normal or slightly reduced, resulting in an IgG1:IgG2 ratio of at least 10:1. Most cases are marked by the presence of anti-extractable nuclear antigen (anti-ENA) antibodies and high titres of rheumatoid factor and antinuclear antibody. All but one patient has a connective tissue disease, nearly twice the prevalence found in similarly hypergammaglobulinaemic patients without this IgG subclass imbalance. Among patients with systemic lupus erythematosus (SLE), those with the IgG1 disorder have a higher prevalence of high titre rheumatoid factor and antinuclear antibody, but a lower prevalence of anti-double-stranded DNA (anti-dsDNA) antibodies above 30 U/ml. It is suggested that this immunoglobulin abnormality may reflect a unique immunoregulatory dysfunction in these patients.