Anti-cytokine autoantibodies suggest pathogenetic links with autoimmune regulator deficiency in humans and mice

Abstract

Autoimmune polyendocrinopathy candidiasis ectodermal dystrophy (APECED) is a recessive disorder resulting from mutations in the autoimmune regulator (AIRE). The patients' autoantibodies recognize not only multiple organ-specific targets, but also many type I interferons (IFNs) and most T helper type 17 (Th17) cell-associated cytokines, whose biological actions they neutralize in vitro. These anti-cytokine autoantibodies are highly disease-specific: otherwise, they have been found only in patients with thymomas, tumours of thymic epithelial cells that fail to express AIRE. Moreover, autoantibodies against Th17 cell-associated cytokines correlate with chronic mucocutaneous candidiasis in both syndromes. Here, we demonstrate that the immunoglobulin (Ig)Gs but not the IgAs in APECED sera are responsible for neutralizing IFN-ω, IFN-α2a, interleukin (IL)-17A and IL-22. Their dominant subclasses proved to be IgG1 and, surprisingly, IgG4 without IgE, possibly implicating regulatory T cell responses and/or epithelia in their initiation in these AIRE-deficiency states. The epitopes on IL-22 and IFN-α2a appeared mainly conformational. We also found mainly IgG1 neutralizing autoantibodies to IL-17A in aged AIRE-deficient BALB/c mice - the first report of any target shared by these human and murine AIRE-deficiency states. We conclude that autoimmunization against cytokines in AIRE deficiency is not simply a mere side effect of chronic mucosal Candida infection, but appears to be related more closely to disease initiation.

Assessment of interferon-related biomarkers in Aicardi-Goutières syndrome associated with mutations in TREX1, RNASEH2A, RNASEH2B, RNASEH2C, SAMHD1, and ADAR: a case-control study

“…The positive–negative discrimination level was set for each antigen as the mean plus three SD of the LU value of sera previously calculated from 15 healthy controls who were not known to have any medical condition, were physically well at the time of sampling, and were negative for autoantibodies to nuclear, smooth muscle, mitochondrial, and parietal cell antigens. Because of the known association with the presence of high titres of neutralising autoantibodies to type I interferons, 27,28 serum from a patient with autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) was run as a positive control with each assay. 28 …”

“…Because of the known association with the presence of high titres of neutralising autoantibodies to type I interferons, 27,28 serum from a patient with autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) was run as a positive control with each assay. 28 …”

Autoimmune Polyendocrinopathy Candidiasis Ectodermal Dystrophy

“…However, approximately 9 % of patients, especially those with missense mutations or later AIRE truncations, do not neutralize IL-22 [70]. ELISA is not the best method for anti-IL-22 detection because many of the epitopes are conformational and sensitive to flattening onto the plastic surface [30]. The diagnostic sensitivity of IL-22 autoantibodies determined by the LIPS assay is 95 % because only 3 patients from 83 tested were negative (our own unpublished observations).…”

“…Low-titer autoantibodies to type I IFNs can also be found in diseases that are accompanied by increased IFN production (i.e., systemic lupus erythematosus, genetic interferonopathies, and during HIV or HCV infection); however, autoantibody production never reaches the levels observed in APECED patients and the antibodies are rarely neutralizing [25,26]. IFN-binding autoantibodies have been analyzed using an enzyme-linked immunosorbent assay (ELISA) [16,27], europium-based immunoassay [20], radioligand binding assay (RLBA) [28], Luminex [29] and luciferasebased immunoprecipitation system (LIPS) [30,31]. Additionally, bioassays such as the antiviral neutralizing assay (AVINA) [16,17,32] and reporter-based cell assays [33] that enable the determination of the neutralizing capacity of the autoantibodies have been reported.…”

“…For diagnostic purposes, the autoantibodies should be tested against IFN-ω and preferentially at least two different IFN-α subtypes because in rare APECED cases some IFN subtypes are less targeted and may remain undetected [16,27,32]. The anti-IFN autoantibody epitopes in APECED are largely conformational [30]. Therefore, solution-based assays where IFN molecules retain their native conformations have advantages over solid phase assays where the epitopes are lost due to flattening onto the surface.…”