Selective IgA Deficiency and Allergy: A Fresh Look to an Old Story

Selective IgA deficiency (SIgAD) is the most common human primary immune deficiency (PID). It is classified as a humoral PID characterized by isolated deficiency of IgA (less than 7 mg/dL but normal serum IgG and IgM) in subjects greater than 4 years of age. Intrinsic defects in the maturation of B cells and a perturbation of Th cells and/or cytokine signals have been hypothesized to contribute to SIgAD pathogenesis. The genetic basis of IgA deficiency remains to be clarified. Patients with SIgAD can be either asymptomatic or symptomatic with clinical manifestations including allergy, autoimmunity and recurrent infections mainly of the respiratory and gastrointestinal tract. Studies analyzing allergy on SIgAD patients showed prevalence up to 84%, supporting in most cases the relationship between sIgAD and allergic disease. However, the prevalence of allergic disorders may be influenced by various factors. Thus, the question of whether allergy is more common in SIgAD patients compared to healthy subjects remains to be defined. Different hypotheses support an increased susceptibility to allergy in subjects with SIgAD. Recurrent infections due to loss of secretory IgA might have a role in the pathogenesis of allergy, and vice versa. Perturbation of microbiota also plays a role. The aim of this review is to examine the association between SIgAD and atopic disease and to update readers on advances over time at this important interface between allergy and SIgAD.

Clinical profile of patients with Seronegative celiac disease

Background Celiac disease (1) mostly diagnosed base on positive serology and duodenal mucosal atrophy, but some patients have negative serology and their diagnosis have some limitation, it delay in diagnosis likely accompanied a poor prognosis and high risk of developing complications of CD. The aim of this study was determent clinical profile of patients with Seronegative CD (SNCD). Methods in this retrospective study, 1115+8 patients, that evaluated for CD with mucosal atrophy included between 2010 to2020. All patients with IgA deficiency other IgG based serology for diagnosis of celiac was done and if these antibodies were negative consider as possible SNCD. If they had positive DQ2-DQ8, and clinical symptoms or had positive challenge test after12 months of GFD were considered as SNCD. Results of total 1115 patients 27 (2.4%) had seronegative mucosal atrophy of duodenum and diagnosed as a SNCD (96.2% marsh3), the mean age and BMI in SNCD patients were significantly higher than other CD patients (p<0.05). Conclusion The prevalence of SNCD was 2.4% that likely related to over weighting, so clinicians should be considered high possible of seronegative CD in patients with over weighting and mucosal atrophy of duodenum.

STXBP6 and B3GNT6 Genes are Associated With Selective IgA Deficiency

Immunoglobulin A Deficiency (IgAD) is a polygenic primary immune deficiency, with a strong genetic association to the human leukocyte antigen (HLA) region. Previous genome-wide association studies (GWAS) have identified five non-HLA risk loci (IFIH1, PVT1, ATG13-AMBRA1, AHI1 and CLEC16A). In this study, we investigated the genetic interactions between different HLA susceptibility haplotypes and non-MHC genes in IgAD. To do this, we stratified IgAD subjects and healthy controls based on HLA haplotypes (N = 10,993), and then performed GWAS to identify novel genetic regions contributing to IgAD susceptibility. After replicating previously published HLA risk haplotypes, we compared individuals carrying at least one HLA risk allele (HLA-B*08:01-DRB1*03:01-DQB1*02:01 or HLA-DRB1*07:01-DQB1*02:02 or HLA-DRB1*01-DQB1*05:01) with individuals lacking an HLA risk allele. Subsequently, we stratified subjects based on the susceptibility alleles/haplotypes and performed gene-based association analysis using 572,856 SNPs and 24,125 genes. A significant genome-wide association in STXBP6 (rs4097492; p = 7.63 × 10−9) was observed in the cohort carrying at least one MHC risk allele. We also identified a significant gene-based association for B3GNT6 (PGene = 2.1 × 10–6) in patients not carrying known HLA susceptibility alleles. Our findings indicate that the etiology of IgAD differs depending on the genetic background of HLA susceptibility haplotypes.

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-DQB 1 ∗ 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-DQB 1 ∗ 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-DQB 1 ∗ 02 allelic variants coding the DQ2 heterodimer. Further and specific studies are needed to make final conclusions in this regard.

Clinical case of congenital CMV neuroinfection in a child with selective IgA deficiency

Congenital CMV infection is thought to occur in at least 1 % of infants, although recent clinical studies indicate that these lesions account for 8 % of all neonates. The severity of clinical symptoms of nervous system damage of CMV-etiology depends on the duration of intrauterine infection. In early infection, during the first trimester of the fetal period, severe CNS malformations develop, including anencephaly, porencephaly, schizencephaly, lissencephaly, micropolygyria, and pachygyria. At later infection, during the 2nd–3rd trimesters of pregnancy, there are milder manifestations — ventriculomegaly, impaired myelination of the white matter of the brain, cysts in the poles of the temporal lobes, hypogenesis of the corpus callosum, periventricular calcifications, and lesions of the cochleovestibular nerves. The article presents the medical history of a 5-year-old boy with typical clinical and instrumental signs of congenital CMV infection. The child had deep spastic tetraparesis, severe mental retardation, refractory epileptic syndrome with polymorphic seizures, disorders of pelvic organs, inability to move independently. MRI of the brain showed typical radiological signs of congenital CMV infection: cortical atrophy, ventriculomegaly, periventricular gliosis, demyelination fields in the white matter of the hemispheres, cysts in the poles of the temporal lobes, hypoplasia of the corpus callosum. During the neonatal period, specific IgM to CMV in serum was observed. Blood leukocyte PCR revealed the CMV DNA in a 5-year-old child at the time of admission to the clinic. This infection led to genera-lized lymphadenopathy, hepatosplenomegaly, thrombocytopenia, and lymphomonocytosis. The assessment of immune status showed the presence of selective IgA deficiency, which was associated with the development of this opportunistic infection. Typical mistakes in the clinical management of children with congenital CMV infection and ways to avoid them are discussed.

Simple Measurement of IgA Predicts Immunity and Mortality in Ataxia-Telangiectasia

Patients with ataxia-telangiectasia (A-T) suffer from progressive cerebellar ataxia, immunodeficiency, respiratory failure, and cancer susceptibility. From a clinical point of view, A-T patients with IgA deficiency show more symptoms and may have a poorer prognosis. In this study, we analyzed mortality and immunity data of 659 A-T patients with regard to IgA deficiency collected from the European Society for Immunodeficiencies (ESID) registry and from 66 patients with classical A-T who attended at the Frankfurt Goethe-University between 2012 and 2018. We studied peripheral B- and T-cell subsets and T-cell repertoire of the Frankfurt cohort and survival rates of all A-T patients in the ESID registry. Patients with A-T have significant alterations in their lymphocyte phenotypes. All subsets (CD3, CD4, CD8, CD19, CD4/CD45RA, and CD8/CD45RA) were significantly diminished compared to standard values. Patients with IgA deficiency (n = 35) had significantly lower lymphocyte counts compared to A-T patients without IgA deficiency (n = 31) due to a further decrease of naïve CD4 T-cells, central memory CD4 cells, and regulatory T-cells. Although both patient groups showed affected TCR-ß repertoires compared to controls, no differences could be detected between patients with and without IgA deficiency. Overall survival of patients with IgA deficiency was significantly diminished. For the first time, our data show that patients with IgA deficiency have significantly lower lymphocyte counts and subsets, which are accompanied with reduced survival, compared to A-T patients without IgA deficiency. IgA, a simple surrogate marker, is indicating the poorest prognosis for classical A-T patients. Both non-interventional clinical trials were registered at clinicaltrials.gov 2012 (Susceptibility to infections in ataxia-telangiectasia; NCT02345135) and 2017 (Susceptibility to Infections, tumor risk and liver disease in patients with ataxia-telangiectasia; NCT03357978)