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Targeted deletion of the IgA constant region in mice leads to IgA deficiency with alterations in expression of other Ig isotypes.

A murine model of IgA deficiency has been established by targeted deletion of the IgA switch and constant regions in embryonic stem cells. B cells from IgA-deficient mice were incapable of producing IgA in vitro in response to TGF-beta. IgA-deficient mice expressed higher levels of IgM and IgG in serum and gastrointestinal secretions and decreased levels of IgE in serum and pulmonary secretions. Expression of IgG subclasses was complex, with the most consistent finding being an increase in IgG2b and a decrease in IgG3 in serum and secretions. No detectable IgA Abs were observed following mucosal immunization against influenza; however, compared with those in wild-type mice, increased levels of IgM Abs were seen in both serum and secretions. Development of lymphoid tissues as well as T and B lymphocyte function appeared normal otherwise. Peyer's patches in IgA-deficient mice were well developed with prominent germinal centers despite the absence of IgA in these germinal centers or intestinal lamina propria. Lymphocytes from IgA-deficient mice responded to T and B cell mitogens comparable to those of wild-type mice, while T cells from IgA-deficient mice produced comparable levels of IFN-gamma and IL-4 mRNA and protein. In conclusion, mice with targeted deletion of the IgA switch and constant regions are completely deficient in IgA and exhibit altered expression of other Ig isotypes, notably IgM, IgG2b, IgG3, and IgE, but otherwise have normal lymphocyte development, proliferative responses, and cytokine production.

Animals↗

The frequency of selective IgA deficiency in myasthenia gravis.

The frequency of selective IgA deficiency is unknown in myasthenia gravis. We screened a series of 333 consecutive adult myasthenic patients for selective IgA deficiency and found only one patient with a selective IgA deficiency, which is not significantly different from the normal population. Organ-specific autoimmune diseases may differ from systemic autoimmune diseases concerning their frequency of association with selective IgA deficiency.

Adult↗

[Selective IgA deficiency and malabsorption. Review of the literature apropos of a case].

One of the most common primary immunodeficiencies is the selective deficiency of IgA, which is present in very variable clinical conditions. This situation had conducted to different criteria with respect to the clinical meaning in a particular patient. The association of immunodeficiency of IgA and intestinal malabsorption is reported as statistically significant in the international literature. Nevertheless, the precise pathogenic connection between them is unknown. The relationship between bowel and immune system is reviewed here, and illustrated with the clinical case of a six-year old girl who presented with malabsorption and selective deficiency of IgA.

Child↗

Epilepsy and IgA deficiency--the effect of sodium valproate.

IgA deficiency (less than 80 IU/ml serum) occurred in 29% of 41 epileptic patients on anticonvulsant therapy. Sodium valproate users had significantly lower mean IgA levels (102 IU/ml) than non-users (151 IU/ml) and had a significantly higher incidence of IgA deficiency (50%) than non-users (16%). The occurrence of IgA deficiency did not appear to be related to age, sex, number of drugs used or to serum anticonvulsant levels.

Adult↗

IgA deficiency: a report of three cases from Thailand.

Selective IgA deficiency has been reported to be the most common primary immunodeficiency disease in Western countries. A markedly lower frequency of this condition has been reported in the Japanese population. While most of the IgA deficient cases are healthy, some patients develop significant recurrent sinopulmonary infections, allergic disorders and autoimmune diseases. Herein, we report three cases of IgA deficiency among Thai patients, all of whom suffered from chronic sinopulmonary infections. Two of the three patients had absolute IgA deficiency while the third had a partial IgA deficiency. The associated conditions found in these three patients were deficiencies of an IgG subclass, allergic rhinitis and lupus nephritis. The youngest child (5 years old boy with lupus nephritis) expired from Pneumocystis carrinii pneumonia complicated with adult respiratory distress syndrome.

Adolescent↗

Anti-IgA antibodies in two brothers with selective serum IgA deficiency.

A selective serum IgA deficiency with anti-IgA antibodies at high titer were found in a patient who suffered severe transfusion reactions. The same abnormalities were detected in his brother, a 72-year-old-man in good general condition. Anti-IgA antibodies were found in the IgG fraction and were directed against alpha-chains. A deficiency of isoagglutinins and an absence of heteroagglutinins in the propositus' serum could be shown.

Aged↗

Role of IgA in the defense against respiratory infections IgA deficient mice exhibited increased susceptibility to intranasal infection with Mycobacterium bovis BCG.

IgA is the predominant Ig isotype in mucosal tissue and is believed to be involved in defense against viral and bacterial infections at these sites. Here, we examined the role of IgA in the protection against intranasal (i.n.) infection with Mycobacterium bovis Bacillus Calmette-Guerin (BCG). IgA deficient (IgA-/-) mice and wild type non-targeted littermate (IgA+/+) mice were immunized by i.n. route with the mycobacterium surface antigen PstS-1 formulated with cholera toxin (CT). Our data showed that IgA-/- mice were more susceptible to BCG infection compared to IgA+/+ mice, as revealed by the higher bacterial loads in the lungs and bronchoalveolar lavage (BAL). Analysis of the Ig levels and the antibody responses to PstS-1 showed that IgA-/- mice had no detectable IgA either in the saliva or in the BAL. However, these mice displayed higher levels of total and specific IgM than IgA+/+ mice in both mucosal fluids. More importantly, analysis of the cytokine responses revealed a reduction in the IFN-gamma and TNF-alpha production in the lungs of IgA-/- compared to IgA+/+ mice. Altogether, our results suggest that IgA may play a role in protection against mycobacterial infections in the respiratory tract by blocking the pathogen entrance and/or by modulating the pro-inflammatory responses.

ATP-Binding Cassette Transporters↗

Long-term follow-up of health in blood donors with primary selective IgA deficiency.

A 20-year health follow-up study of 159 initially healthy blood donors with a severe deficiency of serum IgA ( < 0.05 x 10(-3) g/L) and of 45 donors with decreased serum IgA (0.05 x 10(-3)-0.8 g/L) was carried out. The findings indicate that persons with a severe deficiency of and decreased serum IgA who are healthy as young adults have an increased susceptibility to pneumonia and recurrent episodes of other respiratory infections and a higher risk of developing autoimmune diseases in middle age. Vitiligo, autoimmune hypothyreosis, milk intolerance, and possible rheumatoid arthritis were associated with severe IgA deficiency, but otherwise different degrees of IgA deficiency seem to be similar with respect to the appearance of diseases. Regardless of the fact that a total of 163 (80%) of the 204 IgA-deficient subjects had-episodes of infections, drug allergy, or autoimmune or atopic disease, the finding of primary, selective IgA deficiency in a healthy adult per se does not seem to predict severe life-threatening illnesses at least during 20 years of life.

Adolescent↗

Variable increases of IgG and IgM antibodies in milk of IgA deficient women.

Serum, milk and saliva from seven IgA deficient mothers were studied for the presence of IgA, IgG and IgM antibodies to Escherichia coli and poliovirus antigens. Different variable patterns were obtained. One mother had very much increased IgM and IgG antibodies in milk and saliva against both antigens; the milk IgG antibodies were 11-14 times higher than the reference milk pool. Another mother showed also striking increases of both IgM and IgG antibodies in milk, as well as in saliva where the increases were much higher for the poliovirus than the E. coli antibodies. Yet another mother showed a certain increase of IgM but not of IgG antibodies in the milk. The uneven appearance of IgG and IgM antibodies in serum and secretions suggests local production. So do the differences of antibody avidities, the variations in IgG subclass distribution of antibodies and different patterns after isoelectric focusing (IEF)/immunoblotting analysis of antibody spectrotypes in secretions and serum. The study illustrates the variable patterns of compensatory increases of IgG and IgM antibodies which may occur in IgA deficiency. It also shows that the milk from IgA deficient mothers can still be rich in antibodies, in spite of the lack of secretory IgA.

Antibodies, Bacterial↗

IgA deficiency with membranous glomerulonephritis: a case report and review.

Selective immunoglobulin A (IgA) deficiency may result in a predisposition to recurrent sinopulmonary infection and allergic diseases. IgA deficiency may also play a role in the development of autoimmune disorders. Selective IgA deficiency associated with glomerulonephritis was rare, while the clinical presentation in IgA deficiency-associated glomerulonephritis was variable. We report an 83 year-old male with selective IgA deficiency associated with membranous glomerulonephritis. He presented with nephrotic syndrome. Percutaneous renal needle biopsy showed diffuse global thickening and rigidity of glomerular capillary walls, mildly diffuse segmental expansion of mesangial matrix, focal and cortical scar with segmental obsolescence of glomeruli. Heavy IgG and moderate C3 deposits were found on immunofluorescence. We also review the previous cases of IgA deficiency with glomerulonephritis. Several clues were rendered to establish the association between IgA deficiency and membranous glomerulonephritis.

Aged↗

Comparison of IgG subclasses in foetal serum, maternal serum at delivery and milk in IgA-deficient and control women.

Immunoglobulin G subclass concentrations were measured in paired foetal (cord) and maternal serum specimens at delivery from 27 IgA-deficient (serum IgA < 0.01 g/l) and 15 control women. IgA-deficient women had significantly higher serum IgG1 and IgG3 concentrations than control women but 2 of the group had concomitant IgG2/IgG4 deficiency and a further 12 had low IgG4 concentrations (serum IgG4 < 0.025 g/l). Foetal serum also had significantly higher IgG1 concentrations than control foetal serum but lower IgG2 and IgG4 levels. Concentrations of IgG subclasses and IgM were measured in breast milk collected on the fifth day postpartum from 19 of these IgA-deficient and 18 control women. Between-group differences in IgG subclass levels resembled those in serum. Compared with serum, proportionally less IgG3 was present in milk in both groups although the contribution of IgG3 to total IgG was not less than that of IgG4. Slightly higher IgM was found in milk from the IgA-deficient mothers.

Case-Control Studies↗

Cytokine production in transient hypogammaglobulinemia and isolated IgA deficiency.

BACKGROUND: Transient hypogammaglobulinemia of infancy and isolated IgA deficiency are characterized by normal numbers of circulating B lymphocytes. It is likely that no single abnormality, but rather different factors, may be relevant for the delayed onset of IgG synthesis in transient hypogammaglobulinemia or for the differentiation defect of B cells in IgA deficiency. These factors may include defective production of cytokines or an abnormal response of B cells to various mediators. Alternatively, some cytokines may act as inhibitory factors of B-cell function. METHODS: The ability of peripheral blood mononuclear cells from children with proved or probable transient hypogammaglobulinemia (30 patients) and IgA deficiency (15 patients) to secrete several cytokines on stimulation with phytohemagglutinin in vitro was analyzed. RESULTS: An enhanced production of tumor necrosis factor (TNF)-alpha, TNF-beta, and IL-10 was observed in transient hypogammaglobulinemia; whereas secretion of IL-1, IL-4, and IL-6 was essentially similar in the control and patient groups. Increased frequency of mononuclear cells secreting TNF-alpha was seen in the patient groups. Apart from elevated production of TNF-alpha, no other abnormalities in cytokine synthesis in selective IgA deficiency were observed. In vitro observations showed that exogenously added TNF-alpha and TNF-beta inhibited IgG and IgA secretion by pokeweed mitogen-stimulated mononuclear cells. During follow-up of 10 children, normalization of serum IgG level was associated with a decrease in previously elevated TNF-alpha and TNF-beta production, but IL-10 production remained unchanged. CONCLUSION: These results suggest that TNF may be involved in the regulation of IgG and IgA production and can be associated with an arrest of IgG and IgA switch of B cells in hypogammaglobulinemia. The balance between TNF and IL-10 may be important for the normal development of IgG-secreting B cells.

Agammaglobulinemia↗

Macroamylasaemia and selective IgA deficiency.

Macroamylasaemia and selective IgA deficiency were diagnosed in a 2 year old child who presented with persistent hyperamylasaemia. Macroamylasaemia is an isolated biochemical abnormality caused by aggregation of serum amylase activity with immunoglobulins. Early recognition of macroamylasaemia is important to avoid diagnosing pancreatic disease.

Amylases↗

The prevalence of selective IgA deficiency in type 1 diabetes mellitus.

A significant increase in the prevalence of selective IgA deficiency has been observed in patients with autoimmune disorders such as systemic lupus erythematosus and rheumatoid arthritis. Insulin-dependent diabetes mellitus (IDDM) is an autoimmune disease and susceptibility to both IDDM and IgA deficiency is associated with HLA DQB1 alleles encoding non-Asp amino acids at position 57. In order to assess whether the prevalence of selective IgA deficiency is increased in IDDM, we have screened a homogeneous series of adult patients with IDDM for selective IgA deficiency. One patient (1:261) was found to have a selective IgA deficiency. The prevalence of selective IgA deficiency among adult French blood donors is 1:1400. Thus, although IDDM and selective IgA deficiency are both associated with the presence of non-Asp amino acids at position 57 of the HLA DQ beta chain, the frequency of this immunodeficiency in adult IDDM patients is not significantly increased.

Autoimmune Diseases↗

IgA deficiency and membranous glomerulonephritis presenting as nephrotic syndrome.

Selective IgA deficiency associated with glomerulonephritis is rare and no previous reports in childhood have been made of the association of IgA deficiency and membranous glomerulonephritis (MGN). We report a 5-year-old boy with selective IgA deficiency and MGN. He presented with nephrotic syndrome. Percutaneous renal needle biopsy showed diffuse global thickening on light microscopy and heavy IgG and moderate C3 deposits were found on immunofluorescence. Electron microscopy detected extensive global subepithelial deposition of electron-dense material with frequent intramembranous extension and spike formation. The pathological diagnosis was diffuse MGN stage 1. Oral prednisolone (1 mg kg(-1) day(-1)), angiotensin-converting enzyme inhibitors (ACEI), and angiotensin II receptor blocker (ARB) were given resulting in reduction of proteinuria. The prednisolone dose was gradually tapered and discontinued after 2 months. At present the patient has been in complete remission for 10 months despite the discontinuance of prednisolone. In conclusion, our treatment with corticosteroid, ACEI and ARB reduced proteinuria and was effective for our case with selective IgA deficiency and MGN.

Biopsy, Needle↗

Selective IgA deficiency in Australian blood donors.

Selective serum IgA deficiency (defined as a serum IgA level less than 50 mg/l) was detected in 14 of 6,191 Australian blood donors screened by double diffusion analysis of serum specimens in agarose. This prevalence rate of 0.23% (1 in 442) is the same as that found in blood donors in Sweden but is higher than rates found in blood donors in France (0.05%), Norway (0.08%), USA (0.15%). England (0.19%) and Finland (0.20%). Antibodies to human IgA were detected in the serum of three of 11 blood donors with selective IgA deficiency (27%). There was no evidence in the present study of blood transfusion reactions from these anti-IgA antibodies when they were transfused into recipients.

Adolescent↗

Transfer of IgA deficiency to a bone-marrow-grafted patient with aplastic anaemia.

IgA deficiency developed in a 2-year-old boy with aplastic anaemia who received a bone-marrow graft from his HLA-identical, 6-year-old, IgA-deficient sister. Southern blot analysis revealed the presence of alpha-genes in both children, thus suggesting a defect of lymphocyte stem-cell differentiation as a cause of IgA deficiency. Tissue typing showed homozygosity of HLA A1, B8, DR3, the haplotype associated with IgA deficiency in healthy people. Despite normal serum levels of IgG subclasses in both donor and recipient, both children showed a relative lack of specific IgG2 anticarbohydrate antibodies. This suggests that their IgA deficiency is part of a more fundamental aberration of immunoglobulin class and subclass distribution.

Anemia, Aplastic↗

Immunological study of IgA deficiency during anticonvulsant therapy in epileptic patients.

Of 10 epileptic children with IgA deficiency, one showed normal IgA synthesis and secretion on in vitro pokeweed mitogen (PWM) stimulated lymphocyte culture in contrast to IgA deficiency in vivo, two showed IgA synthesis in cytoplasm without any release of IgA into the supernatant and seven failed to synthesize IgA. Co-cultures with allogeneic T or B cells in various combinations with PWM showed intrinsic IgA-B cell defect without T cell defect in two of the second group affected at IgA secretion and in five of the third group, and intrinsic IgA-B defect with dysfunction of T cells in two of the third group. Thus, the IgA deficiency in these epileptic patients was demonstrated to be heterogenous.

Adolescent↗