Membrane receptors for the IgG4 subclass on human basophils and mast cells

Factors influencing functional abdominal pain in children

Functional gastrointestinal disorders (FGIDs) commonly affect children and are associated with short- and long-term morbidity. Although the pathogenesis of pain-related FGIDs remains incompletely understood, most investigators agree on a multifactorial etiology and the presence of an altered brain-gut interaction. A continuous interplay of genetic and environmental factors appears to shape the development of the central and enteric nervous systems. The biopsychosocial model is the current operational framework for children with FGIDs, as it recognizes the interaction between social and environmental influences and psychological and physiologic processes. The biopsychosocial model proposes that specific permutations of genetic susceptibility, early life experiences, sociocultural issues, and coping mechanisms could explain the variability in clinical presentation and outcome among individuals.

A comparison of the characteristics of circulating anti-myeloperoxidase autoantibodies in vasculitis with those in non-vasculitic conditions

Although circulating anti-neutrophil cytoplasmic antibodies (ANCA) specific for myeloperoxidase (MPO) are strongly associated with the presence of vasculitis, they have been described in sera from patients with other conditions. High levels of anti-MPO antibodies can also persist in sera from patients with vasculitis despite the achievement of clinical remission. One possible interpretation is that a potentially pathogenic subset of anti-MPO antibodies exists, which is only present in patients with active vasculitis. We therefore compared the characteristics of anti-MPO antibodies in sera from patients with active vasculitis (n = 18) with those present in remission (n = 9) and in a disease control group (n = 10) without clinical evidence of vasculitis. The class, subclass and ability of anti-MPO antibodies from the three groups of patients to recognize three different conformational epitopes were analysed using ELISA-based techniques. The expression of an idiotope, designated 9G4, was also examined. Epitope recognition by anti-MPO antibodies from all patients tested was found to be similar. Sera from patients with active vasculitis showed an over-representation of IgG4 subclass anti-MPO antibodies and a more frequent presence of IgM class anti-MPO antibodies. In disease controls, IgG1 anti-MPO antibodies were predominant. In vitro, neutrophil activation by ANCA has been shown to be dependent on engagement of neutrophil FcgammaRIIa receptors following binding of these autoantibodies to surface-expressed ANCA antigens. We found that active vasculitis may be associated with the presence of circulating anti-MPO antibodies which do not significantly bind this receptor, suggesting that mechanisms other than those dependent on FcgammaRIIa binding should be explored. In addition, the expression of the 9G4 idiotope on anti-MPO antibodies in 60% (12/18) of patients with active vasculitis and 20% (2/10) of disease control patients may indicate a common origin for anti-MPO antibodies in different individuals.

Significant correlation between symptom score and IgG4 antibody titer following long-term immunotherapy for perennial allergic rhinitis

Although there is evidence of some measure of clinical benefit as well as immunologic change during the early phase of immunotherapy, a sustained clinical response is only possible with prolonged therapy. Immunotherapy has to be administered for about 3 to 5 years for such sustained clinical efficacy. This study aimed at investigating the dynamics of IgE and IgG4 antibodies after more than 5 years of immunotherapy, to examine the statistical correlation between these antibodies and symptom scores. Our study demonstrated that the allergen-specific IgE antibody level significantly decreases and the IgG4 antibody level significantly increases following immunotherapy. However, the percent decrease in IgE antibodies did not correlate with the percent decrease in symptom scores. On the other hand, the percent increase in IgG4 antibodies correlated with the percent decrease in symptom scores. We infer that an elevation of IgG4 antibodies is not simply an epiphenomenon unrelated to the underlying working mechanism of clinically successful immunotherapy, but probably makes an active contribution to symptom relief.

Contribution of thromboxane A2 to the antigen-induced immediate asthmatic response mediated by IgG1 antibody by augmentation of bronchial responsiveness in guinea-pigs

1. IgG1-mediated anaphylactic bronchoconstriction was elicited by intravenous administration of antigen to guinea-pig 2 days after passive sensitization with IgG1-rich serum, and this response was not affected by heating the serum (at 56 degrees C, for 4 h). IgE-mediated bronchoconstriction, provoked 14 days after passive sensitization with IgE-rich serum, was completely abolished by the heating of the serum. 2. S-1452 (10 mg kg-1, p.o.), a selective thromboxane (Tx) A2 antagonist, significantly but incompletely suppressed the IgG1-mediated bronchoconstriction, but did not affect the IgE-mediated one, while diphenhydramine (5 mg kg-1, i.v.), a histamine antagonist, almost completely inhibited both IgG1- and IgE-mediated bronchoconstriction. 3. Pretreatment with propranolol (1 mg kg-1, i.v.), a beta-adrenergic blocker, in addition to diphenhydramine, caused a long-lasting bronchoconstriction following antigen challenge in both animal models. This histamine-independent bronchoconstriction was markedly suppressed by S-1452 at a low dose of 0.1 mg kg-1. 4. A significant increase in bronchial responsiveness to i.v. acetylcholine (ACh), compared to the prechallenge value, occurred as early as 3 min and persisted for 24 h after antigen challenge in the IgG1 model, but was not observed in the IgE model. S-1452 (10 mg kg-1, p.o.) inhibited the IgG1-mediated bronchial hyperresponsiveness, as assessed 60 min after antigen challenge. 5. A marked elevation of TxB2 levels was observed in bronchoalveolar lavage fluid (BALF) 3 min after antigen challenge in the IgG1 model, while levels were not changed in the IgE model. In contrast, the plasma TxB2 level assessed 1 min after antigen challenge was increased in both the IgGI and IgE models.6. The results indicate that the inhibition of IgGl- but not IgE-mediated bronchoconstriction by higher doses of S-1452 may result from the suppression of increased bronchial responsiveness to allergic mediators such as histamine, which is probably due to TxA2 generated in the airway lumen rather than in plasma. In both the IgGI and IgE models, plasma TxA2 appeared to contribute directly to the bronchoconstriction, its action being almost completely masked by histamine-mediated bronchoconstriction.

Determination of immunoglobulin classes and subclasses of sperm immobilizing antibodies in infertile women and the inhibitory effect of IgG4 subclass on the sperm immobilizing antibody activity

Immunoglobulin classes and subclasses of sperm immobilizing antibodies (SI-Abs) in the sera of sterile women were determined by the absorption of patients' sera with Staphylococcus aureus and immunoadsorbents bound with class or subclass-specific anti-human immunoglobulin antibodies. Among 18 patients' sera tested, 16 had the IgG-dominant SI-Abs and the remaining 2 sera contained IgM-dominant SI-Abs. From the former patients' sera, 9 were further studied to determine the IgG subclasses; 6 of them had IgG1-dominant SI-Abs, one IgG2-dominant, and in the other two IgG1 and IgG2 were equally dominant. Interestingly, SI-Ab activities in 6 of the 9 patients' sera increased after absorption of IgG4 subclass and the addition of IgG4 purified from an SI-positive patient to the same patient's serum diminished the SI-Ab activities.

IgG subclasses in human chronic schistosomiasis: over-production of schistosome-specific and non-specific IgG4

IgG subclasses were determined quantitatively in sera from 63 Egyptian men who were infected with Schistosoma mansoni. Total and antigen-specific IgG was measured pre- and post-treatment. Total IgG subclass antibodies were determined by immunoradiometric assay (IRMA) using monoclonal antibodies (MoAbs). The anti-worm and anti-egg specific S. mansoni IgG subclass antibodies were quantitatively measured by ELISA using specific MoAbs and standards obtained by affinity chromatography. Our data show that total IgG of the patients was elevated in the range of two to three times above normal. The magnitude of increase differed markedly among the four subclasses of IgG. The IgG1, IgG2 and IgG3 concentrations were approximately two to four times higher than normal, whereas the IgG4 concentrations was 20 times normal (9000 mg/l). IgG1 and IgG4 tended to dominate the IgG subclass distribution of anti-soluble worm antigen preparation (SWAP) antibodies followed by IgG2 and IgG3. On the other hand, IgG1 and IgG2 dominated the IgG subclass distribution of anti-soluble egg antigen (SEA) antibodies. As with IgG1, IgG2 and IgG3, most IgG4 was non-specific. The role of IgG subclasses in the pathogenesis of schistosomiasis is not clear. However, the high concentration of IgG4 might act as IgE blocking antibody, possibly as anti-idiotypes that may play a role in down-regulation of the immune system when it is challenged with an excess of antigen.

House dust mite-specific IgE, IgG1, and IgG4 antibodies in patients with perennial rhinitis

Serum samples were obtained from patients with house dust mite-sensitive nasal allergies before and 6 months after immunotherapy, and the level of immunoglobulin (Ig)E, IgG1, and IgG4 antibodies in those sera was determined by the enzyme-linked immunosorbent assay. The present data showed that the mite-specific IgG4 antibodies increased in patients who responded well to immunotherapy but not in those who responded poorly. It was suggested from the present study that IgG4 antibodies seem to act as "blocking antibodies" to reduce the allergic reaction in the target organ, and that an increase of allergen-specific IgG4 antibodies following immunotherapy can be of clinical benefit to patients suffering from mite-specific nasal allergy.