Abstract
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.
Highlights
Celiac disease (CD) is a gluten-related systemic immunemediated disorder characterized by a very variable clinical expression, including both gastrointestinal and extragastrointestinal manifestations
The HLA system represents a relevant component of the genetic predisposition to autoimmunity in general, even if the implicated loci and allelic variants are different according to the specific autoimmune disorder [6]
Immunoglobulin A (IgA) may play a regulatory role in the general homeostasis of the immune system: T regulatory cell deficiency was evidenced in 64% of Selective IgA deficiency (SIgAD) patients, and a number of alterations of B cells were described in these patients, all of which may potentially contribute to autoimmunity [66,67,68,69]
Summary
Celiac disease (CD) is a gluten-related systemic immunemediated disorder characterized by a very variable clinical expression, including both gastrointestinal and extragastrointestinal manifestations. It is diagnosed by the demonstration of specific autoantibodies, such as anti-tissue transglutaminase antibody and anti-endomysium antibody (which mainly belongs to the IgA isotype), along with the presence of atrophic (small bowel) enteropathy at the histopathological level [1,2]. SIgAD is significantly associated with CD [1], which can make the diagnosis of the latter disease be more difficult, since the main serological markers are IgA autoantibodies. We discuss SIgAD and CD in the perspective of the HLA system, in order to analyze and assess the specific contribution of these loci in the etiology and Disease Markers pathogenesis of the epidemiological association between these diseases
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