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

An overview of early genetic predictors of IgA deficiency

INTRODUCTION

Inborn errors of immunity (IEIs) refer to a heterogeneous category of diseases with defects in the number and/or function of components of the immune system. Immunoglobulin A (IgA) deficiency is the most prevalent IEI characterized by low serum level of IgA and normal serum levels of IgG and/or IgM. Most of the individuals with IgA deficiency are asymptomatic and are only identified through routine laboratory tests. Others may experience a wide range of clinical features including mucosal infections, allergies, and malignancies as the most important features. IgA deficiency is a multi-complex disease, and the exact pathogenesis of it is still unknown.

AREAS COVERED

This review compiles recent research on genetic and epigenetic factors that may contribute to the development of IgA deficiency. These factors include defects in B-cell development, IgA class switch recombination, synthesis, secretion, and the long-term survival of IgA switched memory B cells and plasma cells.

EXPERT OPINION

A better and more comprehensive understanding of the cellular pathways involved in IgA deficiency could lead to personalized surveillance and potentially curative strategies for affected patients, especially those with severe symptoms.

The Role of HLA in the Association between IgA Deficiency and Celiac Disease

Selective IgA deficiency (SIgAD) is the most frequent primary immune defect. Since SIgAD is not characterized by relevant infectious issues in most cases, it is often diagnosed during the diagnostic work up of several and different autoimmune disorders, which are associated with this primary immune defect. The genetic background of SIgAD is complex and three HLA haplotypes resulted to be more frequently associated with it; in detail, two of them include HLA-DQB1^∗02 allelic variants, which are essential predisposing factors to develop Celiac Disease (CD). Here, we discuss the evidence regarding the role of HLA in the etiopathogenesis of SIgAD and its association with CD. Actually, the HLA region seems to play a modest role in the genetic predisposition to SIgAD and we may speculate that the association with the HLA-DQB1^∗02 alleles (or haplotypes including them) could derive from its link with CD. Indeed, SIgAD and some related immunological alterations are likely to predispose to several autoimmune diseases (with and despite different HLA backgrounds), including CD, which is relatively common and directly associated with the HLA-DQB1^∗02 allelic variants coding the DQ2 heterodimer. Further and specific studies are needed to make final conclusions in this regard.

The epidemiology and clinical feature of selective immunoglobulin a deficiency of Zhejiang Province in China

Background

Selective immunoglobulin A deficiency (SIgAD) is the most common primary antibody deficiency disease and frequently reported in the Western countries. However, large‐scale epidemiologic studies on SIgAD in China are still lacking.

Methods

The clinical information of 555 180 subjects (age >4 years) including the outpatient, inpatient, and healthy subjects who had ordered serum immunoglobulin A, G, M in 9 hospitals of Zhejiang Province in China was collected. The SIgAD individuals were defined as IgA level <0.07 g/L with normal levels of serum IgG and IgM, whose age should be over 4 years, and any other secondary diseases causing SIgAD were also excluded. Then, the geographical and prevalence distribution of SIgAD individuals in Zhejiang Province and patients' clinical characteristics at the time of diagnosis were also reviewed.

Result

Among these 555 180 subjects who had ordered the immunoglobulin evaluation, the prevalence of SIgAD was 109/555180 (0.02%). The ratio of male to female of these SIgAD individuals was 1:1.37, which also included 87 adults (≥18 years) and 22 children (18 > age >4 years). For adults, the common clinical features were infections (43/87, 49.43%), autoimmune disorders (31/87, 35.63%), allergic cases (5/87, 5.75%), and tumor cases (4/87, 4.60%). Additionally, infectious diseases (20/22, 90.91%), autoimmune disorders (4/22, 18.18%), and allergic cases (1/22, 4.55%) were found in 22 children.

Conclusion

We first describe a large cohort of SIgAD individuals of Zhejiang Province in China. The incidence was 0.020%. The common clinical features were infection, autoimmune disorders, tumor, and allergy, and the infection rate was higher in children than the adults.

Selective immunoglobulin A deficiency (SIgAD) primarily leads to recurrent infections and autoimmune diseases: A retrospective study of Chinese patients in the past 40 years

Selective immunoglobulin A deficiency (SIgAD) is considered to be the most common human primary immune-deficiency disease in the world. However, the incidence in China is obviously lower than Caucasian races. The definition of SIgAD has changed over time with the progress of people's understanding. The scientific community did not reach a consensus on the definition until 1999. As a result, many previously reported cases need to be excluded under the current definition. SIgAD can lead to several spectra of diseases including infections and autoimmune diseases. We retrospectively summarized the SIgAD patients in Peking Union Medical College Hospital (PUMCH), and summarized the Chinese SIgAD reported in China and abroad in past 40 years. Fourty three SIgAD patients were confirmed in the study, in which 9 were healthy without clinical symptoms. Of the 34 patients with clinical symptoms, recurrent infections were found in 29 (85.3%) patients; 13 (38.2%) patients were with autoimmune diseases; 6 (17.6%)cases had allergic symptoms; 3 patients (8.8%) were with tumors, only one case (2.9%) had a family history. Compared with other countries, sIgAD patients in China showed similar symptoms, but the rate of recurrent infections and autoimmune diseases were higher than some other countries; most of the allergic symptoms are drug allergy, different with the allergic sequelae reported in other countries, such as asthma, rhinitis, food allergy and atopic dermatitis; and it is rare to have family history in Chinese patients. We also figured out that more female SIgAD patients tend to have more autoimmune diseases than men (P = 0.039).

The clinical implications of selective IgA deficiency

Selective IgA deficiency (SIgAD) is the most common primary immunodeficiency but does not always result in clinical disease. This may in part be due to the definition based on serum IgA, while most IgA is secreted at mucosal surfaces, not amenable to measurement. Clinical complications include increased risk of sinopulmonary infections with bacteria and viruses, gastrointestinal infections with a predilection for Giardia lamblia, a myriad of autoimmune diseases including systemic lupus erythematosus, hyper- and hypo-thyroidism, Type 1 diabetes, celiac disease, and rarely, malignancy. SIgAD must be differentiated from IgA deficiency that may be seen with IgG2 or IgG4 deficiency, specific antibody deficiency, or as an early manifestation prior to a diagnosis of common variable immunodeficiency. Secondary IgA deficiency is increasingly recognized and may be due to medications such as anti-epileptics, or antibiotics with disruption of the microbiome which can influence IgA levels, infections or malignancies. Patients with SIgAD should be monitored at regular intervals and educated to be aware of particular complications. There is a rare chance of development of anti-IgA IgE antibodies in patients with complete deficiency, which can result in anaphylaxis if blood products with IgA are administered. Prophylactic antibiotics may be indicated in some cases, and very rarely, supplemental IgG infusions.

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 long and winding road to IgA deficiency: causes and consequences

INTRODUCTION

The most common humoral immunodeficiency is IgA deficiency. One of the first papers addressing the cellular and molecular mechanisms underlying IgA deficiency indicated that immature IgA-positive B-lymphocytes are present in these patients. This suggests that the genetic background for IgA is still intact and that class switching can take place. At this moment, it cannot be ruled out that genetic as well as environmental factors are involved. Areas covered: A clinical presentation, the biological functions of IgA, and the management of IgA deficiency are reviewed. In some IgA deficient patients, a relationship with a loss-of-function mutation in the TACI (transmembrane activator and calcium-modulating cyclophilin ligand interaction) gene has been found. Many other genes also have been associated. Gut microbiota are an important environmental trigger for IgA synthesis. Expert commentary: Expression of IgA deficiency is due to both genetic and environmental factors and a role for gut microbiota cannot be excluded.

IgA measurements in over 12 000 Swedish twins reveal sex differential heritability and regulatory locus near CD30L

In a broad attempt to improve the understanding of the genetic regulation of serum IgA levels, the heritability was estimated in over 12 000 Swedish twins, and a genome-wide association study was conducted in a subsample of 9617. Using the classical twin model the heritability was found to be significantly larger among females (61%) compared with males (21%), while contribution from shared environment (20%) was only seen for males. By modeling the genetic relationship matrix with IgA levels, we estimate that a substantial proportion (31%) of variance in IgA levels can ultimately be explained by the investigated SNPs. The genome-wide association study revealed significant association to two loci: (i) rs6928791 located on chromosome 6, 22 kb upstream of the gene SAM and SH3 domain containing 1 (SASH1) and (ii) rs13300483 on chromosome 9, situated 12 kb downstream the CD30 ligand (CD30L) encoding gene. The association to rs13300483 was replicated in two additional independent Swedish materials. The heritability of IgA levels is moderate and can partly be attributable to common variation in the CD30L locus.