A portable surface plasmon resonance (SPR) sensor for the detection of immunoglobulin A in plasma.

BACKGROUND: A life-threatening anaphylactic shock can occur if a patient with undiagnosed immunoglobulin A (IgA) deficiency (i.e., IgA levels <500 ng/mL) receives IgA-containing blood, hence the need for a rapid, point-of-care (POC) method for IgA deficiency screening. Enzyme-linked immunosorbent assay (ELISA) is routinely used to detect IgA, but this method requires trained specialists and ≥24 h to obtain a result. We developed a surface plasmon resonance (SPR)-based protocol to identify IgA-deficient patients or donors within 1 h. MATERIALS AND METHODS: The SPR sensor relies on the detection of IgAs captured by primary antibodies adsorbed on the SPR chip and quantified with secondary antibodies. The sensor was calibrated from 0 to 2000 ng/mL in buffer, IgA-depleted human serum, and plasma samples from IgA-deficient individuals. A critical concentration of 500 ng/mL was set for IgA deficiency. The optimized sensor was then tested on eight plasma samples with known IgA status (determined by ELISA), including five with IgA deficiency and three with normal IgA levels. RESULTS: The limit of detection was estimated at 30 ng/mL in buffer and 400 ng/mL in diluted plasma. The results obtained fully agreed with ELISA among the eight plasma samples tested. The protocol distinguished IgA-deficient from normal samples, even for samples with an IgA concentration closer to critical concentration. DISCUSSION: In conclusion, we developed a reliable POC assay for the quantification of IgA in plasma. This test may permit POC testing at blood drives and centralized centers to maintain reserves of IgA-deficient blood and in-hospital testing of blood recipients.

The Utility of IgA-Based Serologic Markers in Diagnosing Celiac Disease in Children 24 Months of Age or Younger.

Current screening guidelines in North America for celiac disease recommend additional IgG based testing for younger children. Our multicenter retrospective study showed that the anti-tissue transglutaminase IgA antibody test should be the recommended initial test in all children, including those ≤24 months of age.

Implementation of National Institute for Health and Care Excellence (NICE) guidance to measure immunoglobulin A with all coeliac screens: can an affordable solution be devised?

There has been a dramatic increase in requests for coeliac disease (CD) serological screening using immunoglobulin (Ig)A tissue transglutaminase antibodies (IgA-tTG). Recently, the UK National Institute for Health and Care Excellence has revised its guidance, recommending that total IgA should also be measured in all samples. This is justified, as false-negative results may occur with IgA deficiency. However, implementation of this guidance will incur considerable expense. Tests that measure IgA-tTG antibodies can detect IgA deficiency, indicated by low background signal. This provides an opportunity to identify samples containing IgA ≤ 0·2g/l, obviating the need for unselected IgA measurement. We investigated the feasibility of this approach in two centres that use the EliA™ Celikey™ assay or QUANTA Lite® enzyme-linked immunosorbent assay to quantify IgA-tTG antibodies. In both cases, total IgA correlated strongly with background IgA-tTG assay signal. Using the Celikey™ assay, a threshold of < 17·5 response units achieved 100% sensitivity (95% confidence intervals 79·4-100%) for detection of IgA ≤ 0·2g/l, circumventing the need for IgA testing in > 99% of sera. A similar principle was demonstrated for the QUANTA Lite® assay, whereby a threshold optical density of < 0·0265 also achieved 100% sensitivity (95% confidence intervals 78·2-100%) for IgA ≤ 0·2 g/l, avoiding unnecessary IgA testing in 67% of cases. These data suggest that CD screening tests can identify samples reliably containing low IgA in a real-life setting, obviating the need for blanket testing. However, this approach requires careful individualized validation, given the divergent efficiency with which assays identify samples containing low IgA.

Oral manifestations of selective IgA-deficiency: review and case-report.

Immunoglobulin A deficiency is the most common primary immunodeficiency defined as decreased serum level of IgA (less than 7 mg/dl) in the presence of normal levels of other immunoglobulin isotypes. Most individuals with IgA deficiency are asymptomatic and identified coincidentally. However, some patients may present with recurrent infections, allergic disorders and autoimmune manifestations, such as diabetes mellitus, Graves disease and celiac disease. The international literature has not produced any kind of review yet about intra-oral manifestations of selective IgA-deficiency. L.S., a 7-year-old Caucasian girl, was examined at our hospital. After she had undergone a professional dental cleaning, a symmetric, bilateral ulcerative gingivitis developed nearby the upper second primary molars. The gingival ulcers were persistent and did not disappear in the following 3 weeks. In the meantime, the young patient reported the presence of gastrointestinal symptoms. IgA serum level was 4.5 mg/dl, while the other isotypes levels were in the common range. The diagnosis of selective IgA-deficiency was formulated and the girl underwent further examination for the specific IgG autoantibodies in celiac disease, which were not present. Consequently, a full prevention program was planned. This case report emphasizes the role of the paediatric dentist in the early detection of systemic disorder, such as the immunological diseases. The oral cavity often reveals to be the first site of manifestation of important systemic diseases. Immunoglobulin A (IgA) deficiency is the most common primary immunodeficiency and is defined as a decrease in serum IgA levels in the presence of normal levels of other immunoglobulin isotypes (1). Serum IgA deficiency was first described in children with ataxia-telangiectasia (2) and has since been identified in other patients, including normal patients. The prevalence of IgA deficiency ranges from 1:223 to 1:1000 in community studies and from 1:400 to 1:3000 in healthy blood donors (3).

Population-Based Screening for Selective Immunoglobulin A (IgA) Deficiency in Lithuanian Children Using a Rapid Antibody-Based Fingertip Test.

BACKGROUND Selective immunoglobulin A (IgA) deficiency is the most common inherited immunodeficiency disorder worldwide. An early diagnosis is advocated because of the increased risk of infections, autoimmune diseases, and allergic reactions. We investigated the usefulness of a rapid point-of-care test in detecting for IgA deficiency in a population with a previously unknown prevalence. MATERIAL AND METHODS Altogether, 1000 children aged 11-13 years from randomly selected Lithuanian schools were enrolled. A point-of-care test with a fingertip sample was used to screen for the presence of IgA deficiency in children whose parents gave consent. Those with suspected IgA deficiency were referred to hospital for further clinical examination and confirmation of the diagnosis. In addition, their medical histories were compared with those of 30 age- and sex-matched healthy controls. RESULTS IgA deficiency was suspected in one girl and in three boys on the basis of the rapid test, and the diagnosis was confirmed for all four cases (prevalence 0.4%, 95% confidence interval 0.16-1.02%). There was no difference in disease history or complications between IgA-deficient children and healthy controls. CONCLUSIONS The rapid antibody test is a practical and accurate method to diagnose selective IgA deficiency in children. The prevalence of IgA deficiency among Lithuanian schoolchildren is 1:250.

The higher frequency of IgA deficiency among Swedish twins is not explained by HLA haplotypes.

Serum immunoglobulin A (IgA) concentrations were determined in 12 600 adult Swedish twins, applying a high-throughput reverse-phase protein microarray technique. The prevalence of IgA deficiency (IgAD) was found to be 1:241 in monozygotic (MZ) twins and 1:198 in dizygotic (DZ) twins. Hence, the prevalence in twins is markedly elevated as compared with the normal Swedish adult population (1:600). The twins did not show a difference in the frequency of HLA haplotypes in comparison with almost 40 000 healthy Swedish controls. As expected, the risk-conveying HLA alleles A*01, B*08 and DRB1*01 were overrepresented among the IgAD twins and were also associated with significantly lower mean serum IgA concentrations in the twin cohort. In contrast, significantly higher mean IgA concentrations were found among individuals carrying the protective HLA alleles B*07 and DRB1*15. Exome sequencing data from two MZ twin pairs discordant for the deficiency showed no differences between the siblings. Model fitting analyses derived a heritability of 35% and indicate that genetic influences are modestly important for IgAD. The probandwise concordance rates for IgAD were found to be 31% for MZ and 13% for DZ twins.

RAG1 deficiency may present clinically as selective IgA deficiency.

BACKGROUND: Recombination-activating gene (RAG) 1 and 2 deficiency is seen in patients with severe combined immunodeficiency (SCID) and Omenn syndrome. However, the spectrum of the disease has recently expanded to include a milder phenotype. OBJECTIVE: We analyzed a 4-year-old boy who was initially given the diagnosis of selective immunoglobulin A deficiency (SIgAD) based on immunoglobulin serum levels without any opportunistic infections, rashes, hepatosplenomegaly, autoimmunity or granulomas. The patient was found to be infected with varicella zoster; however, the clinical course was not serious. He produced antiviral antibodies. METHODS: We performed lymphocyte phenotyping, quantification of T cell receptor excision circles (TRECs) and kappa deleting recombination excision circles (KRECs), an analysis of target sequences of RAG1 and 2, a whole-genome SNP array, an in vitro V(D)J recombination assay, a spectratype analysis of the CDR3 region and a flow cytometric analysis of the bone marrow. RESULTS: Lymphocyte phenotyping demonstrated that the ratio of CD4+ to CD8+ T cells was inverted and the majority of CD4+T cells expressed CD45RO antigens in addition to the almost complete lack of B cells. Furthermore, both TRECs and KRECs were absent. Targeted DNA sequencing and SNP array revealed that the patient carried a deletion of RAG1 and RAG2 genes on the paternally-derived chromosome 11, and two maternally-derived novel RAG1 missense mutations (E455K, R764H). In vitro analysis of recombination activity showed that both RAG1 mutant proteins had low, but residual function. CONCLUSIONS: The current case further expands the phenotypic spectrum of mild presentations of RAG deficiency, and suggests that TRECs and KRECs are useful markers for detecting hidden severe, as well as mild, cases.

Autoimmunity in patients with selective IgA deficiency.

BACKGROUND AND OBJECTIVE: Selective immunoglobulin A deficiency (SIgAD) is the most common primary antibody deticiency. Patients with SIgAD have a greater risk of concomitant autoimmune disorders than healthy individuals. The exact mechanism underlying the relationship between autoimmunity and SIgAD is not fully understood. The aim of this study was to evaluate potential associations between autoimmunity and specific clinical or immunological findings in patients with SIgAD. METHODS: The study population comprised 57 symptomatic patients (65% males) with confirmed SIgAD who were referred to our center. Demographic data and history of autoimmunity were recorded both for patients and for their relatives. Comprehensive clinical and laboratory examinations were performed to investigate autoimmune complications in all the patients. RESULTS: Autoimmune disorders were documented in 17 cases (29.8%; 9 males and 8 females). The most common manifestations were thyroiditis, vitiligo, and hemolytic anemia (3 cases each). Ten patients (17.5%) had a family history of autoimmunity. Significant associations were detected between autoimmunity and increased duration of follow-up (P = .003), serum level of IgM (P = .01), regulatory T-cell count (P = .03), and class-switched memory B-cell count (P = .01). Four cases of autoimmune SIgAD (23.5%) progressed to common variable immunodeficiency during the follow-up period (P = .006). CONCLUSIONS: Autoimmune disorders, autoimmune cytopenia, and Ig subclass deficiency can lead to severe clinical manifestations in patients with SIgAD. Therefore, immunologists and pediatricians should be aware of these conditions.

Caucasian origin of disease associated HLA haplotypes in chinese blood donors with IgA deficiency.

PURPOSE: Selective immunoglobulin A deficiency (IgAD) is the most common primary immunodeficiency in Caucasians with a prevalence of 1:600. However, the prevalence of IgAD is markedly lower in East Asian countries but no genetic studies have been performed on IgAD individuals in the Mongoloid population. METHODS: We investigated the prevalence of IgAD in a large number of Chinese blood donors (n = 39,015) in Shanghai, China. We measured immunoglobulin class, IgG subclass and anti-IgA serum levels among the IgAD donors. These donors were subsequently tissue typed and the allele frequency was compared with the Shanghai bone marrow donor HLA registry. RESULTS: Seventeen IgAD Chinese blood donors were identified, giving a prevalence of 1: 2,295. Two previously identified IgAD blood donor samples were added in the subsequent tests. Most IgAD donors had serum IgG levels above the normal range with no major IgG subclass deficiency and one donor was weakly positive for anti-IgA. Two-thirds of the Chinese IgAD donors carried Caucasian IgAD associated risk haplotypes, including DRB1*0301-DQB1*0201, DRB1*0701-DQB1*0202 and DRB1*0102-DQB1*0501, giving a significantly higher frequency of these haplotypes as compared to the Shanghai bone marrow donor HLA registry. CONCLUSIONS: The prevalence of IgAD in Chinese in this study is markedly lower than in Caucasians. This is the first study to investigate the genetics of IgAD in the Mongoloid population and two-thirds of the Chinese IgAD donors showed a mixture of Caucasian IgAD risk haplotypes. The low prevalence of IgAD could potentially be due to the low frequency of the disease associated risk haplotypes in China.

Relative IgA-deficient recipients have an increased risk of severe allergic transfusion reactions.

BACKGROUND: Absolute IgA deficiency is the most common immunodeficiency in the Western world. These patients are at risk of severe allergic reactions when receiving a transfusion with a plasma-containing blood product. However, it is unclear whether patients with relative IgA deficiency, that is levels below detection on routine assays, are also at risk of severe reactions. This retrospective study evaluated the number of severe allergic transfusion reactions in relative IgA-deficient patients who were transfused with unwashed blood products. STUDY DESIGN AND METHODS: Patients who had an IgA measurement performed for any reason over a 10-year period were compared with a list of transfusion recipients over the same period. Those who had both an IgA measurement and a transfusion were then compared with the transfusion reaction database to determine whether an allergic reaction had been reported, and if so, the severity of the reaction. Patients with IgA concentrations of <7 mg/dL were defined as relative IgA deficient. RESULTS: Of the 22 362 IgA measurements performed on 19 737 patients over 10 years, a total of 168 relative IgA-deficient patients were identified; 39 of these patients were also transfusion recipients and 4 of 39 (10%) experienced a severe allergic transfusion reaction (SALTR). Eight SALTRs were reported amongst 1545 (0·52%) IgA replete transfusion recipients. CONCLUSION: The significantly increased risk of SALTRs in relative IgA-deficient patients warrants consideration of premedications and/or washing of plasma-containing blood products.

Unexpected reactions of the anti-IgA antibody particle gel immunoassay.

BACKGROUND: The cause of allergic transfusion reactions remains often unknown, but in rare cases anti-immunoglobulin A (IgA) antibodies in patients with IgA-deficiency can be found. We report on the use of the DiaMed particle gel immunoassay (PaGIA) for detection of anti-IgA antibodies in patients with allergic transfusion reactions. METHODS: The examination of the suspected adverse reactions included an anti-IgA antibody test (ID-PaGIA Anti-IgA antibody test; DiaMed GmbH, Cressier , Switzerland) and measurement of IgA concentration in the patient's plasma. In the case of a discrepancy IgA subclasses were examined and neutralization of the anti-IgA antibodies by pure IgA was performed. RESULTS: Of 142 patients tested for IgA concentration and anti-IgA antibodies, 8 gave positive results for the anti-IgA antibody test. In seven of these cases (4.9% of the patients tested) IgA levels were found to be normal, and in four of five so tested, the positive result could not be neutralized with purified IgA. Only one patient had confirmed IgA deficiency with anti-IgA antibodies that were neutralized by addition of purified IgA. CONCLUSION: Cause and clinical relevance of a positive reaction of the anti-IgA antibody test in patients with normal total IgA and normal IgA subclasses remains unknown. Because of the high false positive rate we do not recommend this test as a screening test for anti-IgA antibodies when evaluating allergic transfusion reactions, but instead recommend measurement of total IgA in patient's plasma or serum as a primary screen for IgA deficiency with antibodies as a cause of allergic transfusion reaction.

IgA deficiency and mortality: a population-based cohort study.

IgA deficiency has been linked to increased morbidity but data on mortality is lacking. In this population-based prospective cohort study we examined mortality in patients with IgA deficiency compared with the general population. Through six university hospitals in Sweden we identified 2,495 individuals with IgA deficiency (IgA deficiency ≤0.07 mg/L) diagnosed between 1980 and 2012. Each patient with IgA deficiency was matched on age, sex, place of residence, and year of diagnosis with up to 10 general population controls (n = 24,509). Data on education level and emigration status were obtained from Statistics Sweden. Our main outcome measure was all-cause mortality retrieved from the nationwide Causes of Death Register, which includes >99 % of all deaths in Sweden. We used Cox regression to estimate mortality hazard ratios conditioned on the matching factors and adjusted for education level. During 25,367 person-years of follow-up (median 8.3), there were 260 deaths in the IgA deficiency group versus 1,599 deaths during 257,219 person-years (median 8.6) in the general population controls (102 versus 62 deaths per 10,000 person-years; incidence rate difference, 40, 95%CI 28­53, P < .001). This corresponded to a conditional mortality hazard ratio of 1.8 (95%CI 1.6­2.1, P < .001). Relative mortality varied by follow-up time (P < .001) from a hazard ratio of 3.6 (95%CI 2.5­5.3; P < .001) during the first year to 1.9 (95%CI 1.5­2.4; P < .001) year 1­4; 1.9 (95%CI 1.4­2.4; P < .001) year 5-9; 1.5 (1.0­2.2; P = .054) year 10­14.9; and 1.1 (0.7­1.6; P = .66) year 15­25. Effect modification was also seen by age in each stratum of follow-up time, with higher relative mortality in younger than older patients (P < .001). In conclusion, patients with IgA deficiency are at increased risk of death in the first 10 to 15 years after diagnosis.

Celiac disease in Tunisian children: a second screening study using a "new generation" rapid test.

This work aims to estimate celiac disease prevalence in school-children in the island of Djerba and assess rapid method feasibility for screening. We screened 2064 schoolchildren by a rapid method to detect IgA anti-tissue transglutaminase and IgA deficiency. Children with positive results were tested for IgA anti-transglutaminase and anti-endomysium by conventional tests. In positive children, intestinal biopsy was performed. IgA deficiency suspected by rapid method was confirmed by nephelometry. In these cases IgG anti-endomysium was performed. Rapid test was positive in 7 children; conventional serology was positive in all and 6 of them accepted the biopsy. Total villous atrophy was observed in 5 while intestinal mucosa was normal in one. Among children with positive serology, 3 had silent form, 1 chronic diarrhea, one growth failure and 2 had borderline growth. IgA deficiency was suspected in 13 cases and was confirmed in 11 children tested. Prevalence of celiac disease was 0.24-0.34% and that of IgA deficiency 0.5-0.6%. This screening study confirms that celiac disease is relatively common in schoolchildren in Tunisia. It confirms also that even those with symptoms typical for celiac disease escape diagnosis. Rapid test is better accepted by parents and children than test requiring a venous blood sample.

Genome-wide association study identifies TNFSF13 as a susceptibility gene for IgA in a South Chinese population in smokers.

IgA is an important factor in our immune system. There are many diseases associated with it, such as IgA nephropathy, IgA deficiency, and so on. In order to describe the relationship between the genes and the IgA level, we performed a genome-wide association study of serum IgA with 1,999 healthy Chinese men in the first stage and replicated on an independent Chinese sample with 1,496 subjects in the second stage. Association between each SNP with IgA was estimated by multivariate linear regression analysis conditioned on age and smoke. Haplotype analysis for the block around the top SNP was performed. In the first stage, one genomic locus was identified to be significantly associated with IgA. The loci is TNFSF13 (17p13.1; rs3803800; P = 6.26 × 10(-8)). In smoke-specific analysis, rs3803800 was approximately significantly associated with IgA levels in smokers (P = 3.96 × 10(-7)), while no association was observed in nonsmokers (P = 2.28 × 10(-1)). In addition, we performed the haplotype analysis on chromosome 17 with the SNPs around rs3803800. Although the total P value for the haplotype did not acquire significant difference, three haplotypes (TGAG, CACG, and CACA) reached significant (P < 0.05). In conclusion, TNFSF13 could be a susceptible gene which was discovered having relationship with serum IgA level, and smoke might be a factor infecting the IgA level.

Chronic immune activation in common variable immunodeficiency (CVID) is associated with elevated serum levels of soluble CD14 and CD25 but not endotoxaemia.

Common variable immunodeficiency (CVID), the most frequent symptomatic immunoglobulin primary immunodeficiency, is associated with chronic T cell activation and reduced frequency of CD4(+) T cells. The underlying cause of immune activation in CVID is unknown. Microbial translocation indicated by elevated serum levels of lipopolysaccharide and soluble CD14 (sCD14) has been linked previously to systemic immune activation in human immunodeficiency virus/acquired immune deficiency syndrome (HIV-1/AIDS), alcoholic cirrhosis and other conditions. To address the mechanisms of chronic immune activation in CVID, we performed a detailed analysis of immune cell populations and serum levels of sCD14, soluble CD25 (sCD25), lipopolysaccharide and markers of liver function in 35 patients with CVID, 53 patients with selective immunoglobulin (Ig)A deficiency (IgAD) and 63 control healthy subjects. In CVID subjects, the concentration of serum sCD14 was increased significantly and correlated with the level of sCD25, C-reactive protein and the extent of T cell activation. Importantly, no increase in serum lipopolysaccharide concentration was observed in patients with CVID or IgAD. Collectively, the data presented suggest that chronic T cell activation in CVID is associated with elevated levels of sCD14 and sCD25, but not with systemic endotoxaemia, and suggest involvement of lipopolysaccharide-independent mechanisms of induction of sCD14 production.

Immunoglobulin deficiencies: the B-lymphocyte side of DiGeorge Syndrome.

DiGeorge syndrome is associated with a T-lymphocyte immunodeficiency. The prevalence of hypogammaglobulinemia has not been reported. We found that 3% of patients with DiGeorge syndrome were receiving immunoglobulin replacement therapy and 6% of patients over the age of 3 years had hypogammaglobulinemia. We conclude that DiGeorge syndrome is associated with significant humoral immune deficiency.

Evaluation of particle gel immunoassays for the detection of severe immunoglobulin A deficiency and anti-human immunoglobulin A antibodies.

BACKGROUND: Immunoglobulin A (IgA)-deficient patients with anti-IgA (Ab) require transfusions using blood components with less than 0.05 mg IgA/dL as they are known to be safe for these patients. Identification of severely IgA-deficient (IgA SD) donors involved preliminary screening by the Ouchterlony double immunodiffusion assay followed by confirmatory testing at the required level of sensitivity for IgA and Ab at an external reference laboratory. Two in vitro particle gel immunoassays (ID-PaGIA IgA deficiency test and anti-IgA test) were also evaluated for their suitability in identifying IgA SD individuals and determining their Ab status. STUDY DESIGN AND METHODS: Samples from 198 donors and 36 patients, subjected to confirmatory testing for IgA SD and Ab over a 2-year period, were also evaluated using the ID-PaGIA kits. RESULTS: DiaMed test sensitivity and specificity for detection of IgA SD in donors was 98% whereas for Ab, test sensitivity was 91% at a specificity of 94%. In patients, sensitivity was 94% for IgA SD and 67% for Ab, both tests at a specificity of 100%. CONCLUSIONS: The ID-PaGIA IgA deficiency test was a sensitive and specific tool for identifying IgA SD donors or patients. Sensitivity of the Ab test was high for donors but reduced for patients and of high specificity in both groups. Further studies with patients are needed to confirm this latter observation. Implementation of these tests would make it possible to supply appropriate products from IgA SD donors to prevent anaphylactic transfusion reactions in patients.

Lack of increased prevalence of immunoregulatory disorders in hereditary angioedema due to C1-inhibitor deficiency.

Hereditary angioedema due to deficiency of C1-INH (HAE-C1-INH) is associated with enhanced consumption of the early complement components, which may predispose for autoimmune disease. We assessed the prevalence of such disorders among HAE- C1-INH patients and their impact on the natural course of HAE-C1-INH. Clinical data and immunoserological parameters of 130 HAE-C1-INH and 174 non-C1-INH-deficient patients with angioedema were analyzed. In our study, the incidence of immunoregulatory disorders was 11.5% in the population of HAE-C1-INH patients and 5.2% among non-C1-INH-deficient controls with angioedema. Immunoserology screening revealed a greater prevalence of anticardiolipin IgM (p=0.0118) among HAE-C1-INH patients, than in those with non-C1-INH-deficient angioedema. We did not find higher prevalence of immunoregulatory disorders among our HAE-C1-INH patients. However, in patients with confirmed immunoregulatory disorders, the latter influenced both the severity of HAE-C1-INH and the effectiveness of its long-term management. Appropriate management of the immunoregulatory disease thus identified improves the symptoms of HAE-C1-INH.

Allele *1 of HS1.2 enhancer associates with selective IgA deficiency and IgM concentration.

Selective IgA deficiency (IGAD) is the most common primary immunodeficiency, yet its pathogenesis is elusive. The IG (heavy) H chain human 3' Regulatory Region harbors three enhancers and has an important role in Ig synthesis. HS1.2 is the only polymorphic enhancer of the 3' RRs. We therefore evaluated HS1.2 allelic frequencies in 88 IGAD patients and 101 controls. Our data show that IGAD patients have a highly significant increase of homozygousity of the allele *1 (39% in the IGAD patients and 15% in controls), with an increase of 2.6-fold. Allele *4 has a similar trend of allele *2, both showing a significant decrease of frequency in IGAD. No relationship was observed between allele *1 frequencies and serum levels of IgG. However, allele *1 was associated in IGAD patients with relatively low IgM levels (within the 30th lowest percentile of patients). The HS1.2 polymorphism influences Ig seric production, but not IgG switch, in fact 30th lowest or highest percentile of IgG in patients did not associate to different frequencies of HS1.2 alleles. The control on normal healthy subjects did not correlate high or low levels of IgM or IgG with HS1.2 allelic frequence variation. Overall our candidate gene approach confirms that the study of polymorphisms in human diseases is a valid tool to investigate the function of these Regulatory Regions that confers multiple immune features.