Increased levels of IgG4 subclass in 5 patients with acquired respiratory disease

Spectrum of Disorders Associated with Elevated Serum IgG4 Levels Encountered in Clinical Practice

IgG4-related disease (IgG4-RD) is a recently described systemic fibroinflammatory disease associated with elevated circulating levels of IgG4 and manifests a wide spectrum of clinical presentations. Although serum IgG4 level has been described to be the most sensitive and specific laboratory test for the diagnosis of IgG4-RD, it is recognized that an elevated serum IgG4 level can be encountered in other diseases. In this study, we sought to identify the frequency of IgG4-RD and other disease associations in patients with elevated serum IgG4 levels seen in clinical practice. Among 3,300 patients who underwent IgG subclass testing over a 2-year period from January 2009 to December 2010, 158 (4.8%) had an elevated serum IgG4 level (>140 mg/dL). IgG4 subclass testing was performed for evaluation of suspected IgG4-RD or immunodeficiency. Twenty-nine patients (18.4%) had definite or possible IgG4-RD. Among those patients without IgG4-RD, a broad spectrum of biliary tract, pancreatic, liver, and lung diseases, as well as systemic vasculitis, was diagnosed. We conclude that patients with elevated serum IgG4 levels encountered in clinical practice manifest a wide array of disorders, and only a small minority of them has IgG4-RD.

Polyclonal IgG4 hypergammaglobulinemia associated with plasmacytic lymphadenopathy, anemia and nephropathy

Marked polyclonal immunoglobulin (Ig)G4 hypergammaglobulinemia has exceptionally been reported. Here we report on two Algerian patients who presented a syndrome characterized by anemia, plasmacytic lymphadenopathy, renal manifestations, and a marked polyclonal IgG4 hypergammaglobulinemia leading to a hyperviscosity syndrome in one case. The IgG4-expressing cell percentage was significantly increased in the peripheral blood lymphocytes collected from the two patients upon diagnosis. Moreover, in contrast with normal sera, both patients' sera significantly increased the percentage of IgG4-expressing cells when incubated with CD40-stimulated normal B lymphocytes. Similar effects were obtained with the culture supernatants of the patients' activated T cells. Anti-interleukin (IL) 4 and/or anti-IL-13 antibodies were unable to antagonize the IgG4 production. IL-4 and IL-13 serum concentrations were found to be normal in the two patients. The increased IgG4 production was found to be mediated by soluble factor(s), most probably secreted by activated T cells, which did not require the signal transducer and activator of transcription 6 signaling pathway.

Antibodies of different immunoglobulin isotypes in serum and bile of patients with clonorchiasis

Specimens of serum and bile from patients were assayed by an enzyme-linked immunosorbent assay to reveal antibodies specific to antigens from adult Clonorchis sinensis. Antibodies of the IgG isotype showed the greatest elevation during infection (Student's t-test, P < 0.001), whereas serum IgA and IgE and secretory IgA in bile were moderately elevated (P < 0.05). Major differences in the distribution of antibodies among the IgG subclasses were observed between patients who were and those who were not infected. IgG4 antibody levels were elevated in the serum and bile of infected patients, and there were significant correlations between the levels of IgG and IgG4 antibodies and the intensity of infection.

IgG subclasses in bronchoalveolar lavage fluid from patients with asthma

We have measured Immunoglobulin G (IgG) subclasses in serum and bronchoalveolar lavage fluid (BALF) from 12 non-smoking patients with stable asthma and 9 non-smoking healthy volunteers to obtain information on their possible role in local immunological reactions. The quotients (concentration of IgG subclass in BALF)/(concentration of IgG subclass in serum) were calculated. In controls QIgG3 were lower than QIgG1, QIgG2 and QIgG4. The IgG subclasses in BALF and epithelial lining fluid (ELF) from patients with asthma were significantly higher than in controls, mainly due to increased leakage from the blood. Again QIgG3 were lower than Q of other subclasses. In the analysis of local production of IgG, albumin or ceruloplasmin was used as reference protein. Several patients showed a local production or a preferential accumulation of one or more IgG subclasses. We conclude that in healthy persons the IgG subclasses in ELF originate from the systemic circulation by passive permeation. In patients with asthma, the permeability of the respiratory membrane may be increased resulting in increased concentrations of subclasses in lung-lining fluid. In some patients with asthma, an additional local production of IgG subclasses occurs.

IgG subclass concentrations in sera from 200 normal adults and IgG subclass determination of 106 myeloma proteins: an interlaboratory study

The IgG subclass protein concentrations in sera from 200 normal subjects were determined independently in two laboratories, using the same technique (radial immunodiffusion), the same subclass-specific antibodies and the same calibrator. The coefficients of correlation (rs) between IgG subclass concentrations determined in the two laboratories were 0.487, 0.883, 0.928 and 0.926 for IgG1, IgG2, IgG3 and IgG4, respectively (p less than 0.0005 in all four cases). By the chi-square test for goodness of fit, the frequency distributions observed in the two laboratories were found to differ significantly for all four subclasses (p less than 0.01). In one laboratory, the distributions of IgG1 and IgG2 were not significantly different from normal distributions, whereas the distributions of IgG3 and IgG4 deviated significantly. In the other laboratory, all four subclass distributions were significantly different from normal distributions. In the first laboratory, the IgG2 concentrations were log-normal distributed, whereas in the second, IgG1, IgG2 and IgG4 concentrations were log-normal distributed. We conclude that use of identical reagents does not ensure identical frequency distributions. This finding emphasizes the need for standardization of the measurement technique too. Furthermore, we argue that at present, intralaboratory reference intervals for IgG subclass protein concentrations are necessary. The reference intervals should be based on non-parametric statistics. The subclass of 106 monoclonal IgG proteins, which were demonstrated by agarose gel electrophoresis, was identified by RID for 89 samples. The subclass of the remaining 16 M-components was readily determined by qualitative immunoelectrophoretic analysis using the same subclass-specific antibodies.

Antibody isotypes in human schistosomiasis mansoni

Schistosoma mansoni-infected subjects from the Gezira Irrigated Area of Sudan were studied for serum immunoglobulin levels, and specific antibody titres to larval, adult and egg stage antigens, by class and IgG subclass. The 276 subjects were adult chronic cases (frequently exposed male canal cleaners), primary school children, and hospital-referred cases with acute symptoms including hepatosplenomegaly. Chronic untreated cases were compared with a similar group of canal cleaners 3 months after successful chemotherapy with Praziquantel administered at the start of the non-transmission season. All cases, except those previously treated, were egg positive at the time of blood sampling. Data from infected and treated cases were compared with measurements of serum immunoglobulin in a panel of European blood donors. The major findings are as follows: There is a consistently elevated total serum IgG concentration in infected groups which is accounted for mainly by an increased IgG1 subclass (greatest in chronic cases) and by a remarkable 10- to 11-fold increase in IgG4 in the untreated chronically infected group and in the schoolchildren. All infected groups showed high IgG antibody responses to all life cycle stage antigens, and IgM titres were high to adult and egg antigens in untreated canal cleaners. Major differences were evident in the distribution of IgG subclass antibodies between the infected groups: the response to larval and adult antigens is poor or absent in IgG1, IgG2 and IgG3 in untreated chronic infections but is high in IgG4, whereas in acute cases with hepatosplenomegaly and in school-children IgG1, IgG2 and IgG3 antibodies to larval antigens are in high titre but IgG4 and IgM responses to larvae are low or absent, the response in these isotypes being restricted in these cases to adult and egg antigens. Comparing the treated and untreated canal cleaners, although these are separate groups, the data suggest that Praziquantel reduces total serum IgA and IgM levels but has little effect on the raised IgG component except for the IgG4 subclass. The treated chronic cases show a reversal in the ratio of IgG1, IgG2 and IgG3 to IgG4 antibodies to larval and adult antigens compared with the untreated chronic group-the IgG4 response being low by 3 months after treatment and the IgG1, IgG2 and IgG3 being high. These data are discussed in relation to the possible importance of antibody isotype selection in determining host susceptibility to infection, with reference to age, exposure and treatment of the host.

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

Anti-Sm antibodies are highly specific markers for the diagnosis of systemic lupus erythematosus (SLE). This specificity suggests that the immunoregulation of these autoantibodies would reflect fundamental immune abnormalities in this disorder. As a clue to this immunoregulation, we have investigated the isotype distribution of anti-Sm antibodies by enzyme-linked immunosorbent assays. We have found that the anti-Sm response is markedly restricted to the IgG1 heavy chain isotype. On the other hand, the light chain distribution reflects that in normal serum, while isoelectric focusing analysis fails to show an oligoclonal pattern. The related specificity, anti-ribonucleoprotein, is also restricted to IgG1, while the SLE-specific antibody anti-double-stranded DNA is mostly IgG1 with a lesser contribution by IgG3. These results suggest that antinuclear antibodies that are strongly associated with SLE are produced by a T cell-dependent response, probably driven by antigen. The immunoregulation of the response to several autoantigens may be quite similar.

Sensitive analytic ELISAs for subclass herpes virus IgG

The subclass distribution of antiviral antibodies to three herpes viruses was studied in a population of healthy blood donors. Subclassification by monoclonal antibodies led to the identification of certain viral IgG patterns. IgG1 appeared to be formed in response to almost all CMV, HSV-1 and VZV infections. A higher frequency of virus-specific IgG3 to CMV and HSV-1 suggested that these infections may be reactivated subclinically more often than VZV. The presence of CMV and VZV IgG4 showed a familial relationship, while IgG4 responses to HSV-1 were common. Persons with IgG4 as the only subclass-reactive antibody to CMV showed cell-related reactivities in a high frequency. Patients with leukemias, myelomas and Crohn's disease had a near-normal subclass pattern to the herpes viruses.

Measurement of serum IgG4 levels by a competitive immunoenzymatic assay with monoclonal antibodies

A competitive indirect ELISA is described for the measurement of IgG4 levels. It uses a monoclonal anti-subclass and antibody and purified monoclonal IgG4 as standards. This method is sensitive and reproducible and more accurate than hemagglutination inhibition and radial immunodiffusion. Serum IgG4 levels in 173 normal adults were less than 0.01-2.1 mg/ml (mean 0.30 mg/ml) in women and less than 0.01-1.87 mg/ml (mean 0.465 mg/ml) in men.

A community survey of IgG4 antibody levels

Precise and specific radioimmunoassays have been developed to quantify IgG4 and IgG4 antibodies. A community survey has demonstrated that men have significantly higher total serum IgG4 levels than women: geometric mean values of 0.581 mg/ml versus 0.302 mg/ml. This sex difference was extended to total IgE values. Circulating levels of IgG4 antibodies against foods, especially egg and milk, were normally higher than those against the three most common U.K. inhalant allergens--grass pollen, house dust mite and cat epithelium.