The complex HLA-E-nonapeptide in Behçet disease.

Introduction: The knowledge of the aetiology of Behçet disease (BD), an immune-mediated vasculitis, is limited. HLA-B, mainly HLA-B51, and HLA-A molecules are associated with disease, but the ultimate cause of this association remains obscure. There is evidence that NK cells participate in the etiopathology of BD. NK cells have activator and inhibitor surface receptors, like the KIR and the NKG2 families. Classical HLA-class I molecules (A, B and C) are keys in the activity control of the NK because they are KIR ligands. Most NKG2 receptors bind HLA-E, which presents only nonapeptides derived from the signal peptide of other class-I molecules. Objective: This study investigates the contribution of the pair HLA-E and ligand, nonapeptide derived from the 3-11 sequence of the signal peptides of class I classical molecules, to the susceptibility to BD. Methods: We analyzed the frequency of the HLA-derivated nonapeptide forms in 466 BD patients and 444 controls and an HLA-E functional dimorphism in a subgroup of patients and controls. Results: In B51 negative patients, the frequency of VMAPRTLLL was lower (70.4% versus 80.0% in controls; P=0.006, Pc=0.04, OR=0.60, 95%CI 0.41-0.86), and the frequency of VMAPRTLVL was higher (81.6% versus 71.4% in controls; P=0.004, Pc=0.03, OR=1.78, 95%CI 1.20-2.63). In homozygosity, VMAPRTLLL is protective, and VMAPRTLVL confers risk. The heterozygous condition is neutral. There were no significant differences in the distribution of the HLA-E dimorphism. Discussion: Our results explain the association of BD with diverse HLA-A molecules, reinforce the hypothesis of the involvement of the NK cells in the disease and do not suggest a significant contribution of the HLA-E polymorphism to disease susceptibility.

The role of a functional variant of TYK2 in vasculitides and infections.

OBJECTIVES: The TYK2 gene encodes a tyrosin kinase which is involved in multiple immune functions. A functional variant of this gene has been identified to play a protective role in multiple autoimmune diseases. The goal of this study was to evaluate the involvement of this variant of TYK2 in vasculitides [giant cell arteritis (GCA), ANCA-associated vasculitis (AAV) and IgA vasculitis (IgAV)] and viral infections [hepatitis C virus (HCV) and human immunodeficiency virus type I (HIV-1)]. METHODS: The study sample was composed of 13,745 European individuals. The genotyping was performed by Immunochip and TaqMan 5' allele discrimination assays and the allele frequencies were compared using PLINK. RESULTS: Although the results obtained did not reach the genome-wide level of significance, p-values at nominal significance were observed, suggesting that the TYK2 variant provides protection against two vasculitides: GCA (p=5.94E-3; OR (95%CI) = 0.56 (0.37-0.85) and AAV (p=6.79E-3; OR (95%CI) = 0.65 (0.47-0.89). However, this variant was not found to be associated with IgAV. No evidence was gained that the TYK2 variant confers susceptibility to HCV and HIV-1 infection. CONCLUSIONS: This is the first study to propose the association between the TYK2 and both GCA and AAV. Our findings also suggest that TYK2 does not play a relevant role in IgAV or in susceptibility to HCV and HVI-1.

Association of Functional Polymorphisms of KIR3DL1/DS1 With Behçet's Disease.

Behçet's disease (BD) is an immune-mediated vasculitis related to imbalances between the innate and adaptive immune response. Infectious agents or environmental factors may trigger the disease in genetically predisposed individuals. HLA-B51 is the genetic factor stronger associated with the disease, although the bases of this association remain elusive. NK cells have also been implicated in the etiopathogenesis of BD. A family of NK receptors, Killer-cell Immunoglobulin-like Receptor (KIR), with a very complex organization, is very important in the education and control of the NK cells by the union to their ligands, most of them, HLA class I molecules. This study aimed to investigate the contribution of certain KIR functional polymorphisms to the susceptibility to BD. A total of 466 BD patients and 444 healthy individuals were genotyped in HLA class I (A, B, and C). The set of KIR genes and the functional variants of KIR3DL1/DS1 and KIR2DS4 were also determined. Frequency of KIR3DL1*004 was lower in patients than in controls (0.15 vs. 0.20, P = 0.005, Pc = 0.015; OR = 0.70; 95% CI 0.54-0.90) in both B51 positive and negative individuals. KIR3DL1*004, which encodes a misfolded protein, is included in a common telomeric haplotype with only one functional KIR gene, KIR3DL2. Both, KIR3DL1 and KIR3DL2 sense pathogen-associated molecular patterns but they have different capacities to eliminate them. The education of the NK cells depending on the HLA, the balance of KIR3DL1/KIR3DL2 licensed NK cells and the different capacities of these receptors to eliminate pathogens could be involved in the etiopathogenesis of BD.

Specific Association of HLA-DRB1*03 With Anti-Carbamylated Protein Antibodies in Patients With Rheumatoid Arthritis.

OBJECTIVE: Recognition of a new type of rheumatoid arthritis (RA)-specific autoantibody, the anti-carbamylated protein antibodies (anti-CarP), has provided an opportunity to improve the management and understanding of RA. The current study was undertaken to assess the relationship between anti-CarP antibodies and HLA-DRB1 alleles in RA. METHODS: Serum samples were obtained from 3 different collections, comprising a total of 1,126 RA patients. Serum reactivity against in vitro carbamylated fetal calf serum proteins was determined by enzyme-linked immunosorbent assay. HLA-DRB1 alleles were determined using either hybridization techniques or imputation from HLA-dense genotypes. Results of these analyses were combined in a meta-analysis with data from 3 previously reported cohorts. The carrier frequencies of the common HLA-DRB1 alleles were compared between the antibody-positive RA subgroups and the double-negative subgroup of RA patients stratified by anti-citrullinated protein antibody (ACPA)/anti-CarP antibody status, and also between the 4 RA patient strata and healthy controls. RESULTS: Meta-analysis was conducted with 3,709 RA patients and 2,305 healthy control subjects. Results revealed a significant increase in frequency of HLA-DRB1*03 carriers in the ACPA-/anti-CarP+ subgroup as compared to ACPA-/anti-CarP- RA patients and healthy controls; this was consistently found across the 6 sample collections. This association of HLA-DRB1*03 with ACPA-/anti-CarP+ RA was independent of the presence of the shared allele (SE) and any other confounders analyzed. No other allele was specifically associated with the ACPA-/anti-CarP+ RA patient subgroup. In contrast, frequency of the SE was significantly increased in the ACPA+/anti-CarP- and ACPA+/anti-CarP+ RA patient subgroups, without a significant distinction between them. Furthermore, some alleles (including HLA-DRB1*03) were associated with protection from ACPA+ RA. CONCLUSION: These findings indicate a specific association of HLA-DRB1*03 with ACPA-/anti-CarP+ RA, suggesting that preferential presentation of carbamylated peptides could be a new mechanism underlying the contribution of HLA alleles to RA susceptibility.

Neumonitis por hipersensibilidad como complicación del tratamiento con BCG intravesical por carcinoma de vejiga / Hypersensitivity pneumonitis as a complication of intravesical BCG therapy for bladder cancer

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