La polyendocrinopathie auto-immune de type 1 (PEA1) est liée aux mutations du gène AIRE. En l’absence de AIRE se développe un défaut de tolérance immune centrale, à l’origine de pathologies auto-immunes multiples spécifiques d’organe. Notre objectif était d’évaluer l’effet d’une altération« exemplaire » du répertoire T sur les empreintes auto-réactives humorales. Les données cliniques etimmunologiques ont été recueillies chez des patients atteints de PEA1, qui ont bénéficié du séquençage du gène AIRE. Chez ces patients ont été analysés les profils d’auto-réactivité sérique IgGet IgM vis à vis des tissus pancréatique et surrénalien, en comparaison à des patients atteints d’autres endocrinopathies auto-immunes, et à des sujets sains. Les bandes antigéniques discriminantes ont été sélectionnées grâce à un test de Chi-2, et une approche immuno-protéomique a permis leur caractérisation moléculaire. Dix-neuf patients atteints de PEA1 ont pu être étudiés. Ils présentaient de1 à 10 manifestations cliniques liées à la maladie. Quatre mutations du gène AIRE différentes ont été identifiées, et la délétion 13-bp dans l’ exon 8 (c.967-979del13) s’est avérée la plus fréquente. L’étude en immuno-empreinte a permis d’identifier 6 antigènes préférentiellement reconnus par les patients atteints de PEA1. Leur caractérisation par approche immuno-protéomique a montré qu’il s’agissait à lafois d’antigènes tissus-spécifiques (lipase pancréatique reconnue à la fois par les IgM et les IgG,amylase pancréatique reconnue par les IgG, Regenerating Protein 1 alpha pancréatique ciblée par lesIgM) mais également ubiquitaires (péroxiredoxine-2 reconnue à la fois par les IgG et les IgM, HeatShock cognate 71kDa Protein ciblée par les IgM, aldose réductase reconnue par les IgG). Ainsi, une altération majeure du répertoire T auto-réactif, telle que celle liée aux mutations du gène AIRE, affecte de manière importante les réponses humorales auto-réactives dépendantes d’ IgG, mais également d’IgM. Ces modifications touchent à la fois des antigènes tissu-spécifiques et ubiquitaires, nous faisant évoquer un rôle au moins partiel de AIRE dans des phénomènes T-indépendants et /ou des altérations de l’immunité naturelle. / Autoimmune polyendocrine syndrome type 1 (APS1) is caused by mutations in the AIRE gene thatinduce central tolerance breakdown which results in tissue-specific autoimmune diseases. Ourobjective was to evaluate the effect of a well-defined T cell repertoire impairment on humoralsystemic self-reactive footprints. Clinical and immunological data were collected, and pathologicalmutations in the AIRE gene were identified by DNA sequencing. Comparative serum self-IgG andself-IgM reactivities, directed towards pancreatic and adrenal protein extracts, of APS1 patients,patients suffering from other autoimmune endocrinopathies and healthy subjects, were tested using Western blotting. Discriminant protein bands were selected using the Chi-square test and molecularcharacterization of these bands was conducted using a proteomic approach. Nineteen patients wereidentified with APS1. Clinical manifestations varied greatly, showing 1 to 10 components. Fourdifferent AIRE gene mutations were identified, and the 13-bp deletion in exon 8 (c.967-979del13) wasthe most prevalent. A singular distortion of seric self-IgG and self-IgM repertoires was noted in APS1patients. IgG and IgM antibodies recognized significantly one tissue-specific (pancreatictriacylglycerol lipase) and one ubiquitous antigens (peroxiredoxin-2). IgM recognized one tissuespecific (Pancreatic regenerating protein 1!) and one ubiquitous antigen (Heat Shock cognate 71kDaProtein). IgG also recognized one tissue-specific (pancreatic amylase) and one ubiquitous antigen(aldose reductase). As expected, a well-defined self-reactive T cell repertoire impairment affected thetissue-specific self-IgG repertoire but also self-IgM repertoire. Our study also reveals discriminant responses against ubiquitous antigens with IgG and IgM antibodies. Some common discriminantantigenic targets were found for IgG and IgM. All these data suggest that T cell-dependent but also T cell-independent mechanisms are involved in APS1. The potent involvement of complementary events related to potent dysfunction in the innate immune response is discussed.

Systemic lupus erythematosus (SLE) is the prototypic systemic autoimmune disease, whereas autoimmune polyendocrine syndrome type 1 (APS1) is a rare autosomal disorder characterized by combinations of organ-specific autoimmune manifestations including hypoparathyroidism and intestinal dysfunction, and may serve as a model for organ-specific autoimmunity. Autoantibodies directed against proteins expressed in the affected tissues are found in both diseases. From a chondrocyte cDNA expression library, we identified the protein AHNAK as an autoantigen in SLE. Anti-AHNAK antibodies were found in 29.5% (18/61) of patients with SLE, 4.6% (5/109) of patients with rheumatoid arthritis, and 1.2% (2/172) of blood donors. Using a candidate approach, we analyzed the prevalence in APS1 and other organ-specific autoimmune diseases, of autoantibodies against the pyridoxal phosphate-dependent enzymes histidine decarboxylase (HDC) and cysteine sulfinic acid decarboxylase (CSAD), which are structurally closely related to known autoantigens. Anti-HDC and anti-CSAD reactivity was detected exclusively in APS1 patient sera. Anti-HDC antibodies were detected in 37.1% (36/97) of the APS1 sera, did not cross-react with aromatic L-amino acid decarboxylase, and were associated with intestinal dysfunction and loss of histamine-producing gastric enterochromaffin-like cells. In contrast, anti-CSAD reactivity was detected in 3.6% (3/83) of APS1 sera and cross-reacted with recombinant glutamic acid decarboxylase. From a parathyroid cDNA expression library, novel spliced transcripts of the CLLD4 gene on human chromosome 13q14, encoding 26 and 31 kDa isoforms recognized by autoantibodies in 3.4% (3/87) of APS1 patients, were identified and found to be preferentially expressed in lung and ovary. Both isoforms contain an N-terminal BTB/POZ domain, similarly to the TNF-alpha-regulated protein B12, localize both to the cytoplasm and nucleus in transfected COS cells, and form oligomers in vitro. The CLLD4 gene is located in a region frequently deleted in several forms of cancer, including lung and ovarian tumors. In conclusion, we have identified and partially characterized AHNAK and HDC as two common targets of autoantibodies in SLE and APS1, respectively. We have also identified CSAD and CLLD4 as two minor autoantigens in APS1, one of which is a novel protein with unknown function.