APECED: is this a model for failure of T cell and B cell tolerance?

Abstract

In APECED, the key abnormality is in the T cell defect that may lead to tissue destruction chiefly in endocrine organs. Besides, APECED is characterized by high-titer antibodies against a wide variety of cytokines that could partly be responsible for the clinical symptoms during APECED, mainly chronic mucocutaneous candidiasis, and linked to antibodies against Th17 cells effector molecules, IL-17 and IL-22. On the other hand, the same antibodies, together with antibodies against type I interferons may prevent the patients from other immunological diseases, such as psoriasis and systemic lupus erythematous. The same effector Th17 cells, present in the lymphocytic infiltrate of target organs of APECED, could be responsible for the tissue destruction. Here again, the antibodies against the corresponding effector molecules, anti-IL-17 and anti-IL-22 could be protective. The occurrence of several effector mechanisms (CD4+ Th17 cell and CD8+ CTL and the effector cytokines IL-17 and IL-22), and simultaneous existence of regulatory mechanisms (CD4+ Treg and antibodies neutralizing the effect of the effector cytokines) may explain the polymorphism of APECED. Almost all the patients develop the characteristic manifestations of the complex, but temporal course and severity of the symptoms vary considerably, even among siblings. The autoantibody profile does not correlate with the clinical picture. One could speculate that a secondary homeostatic balance between the harmful effector mechanisms, and the favorable regulatory mechanisms, finally define both the extent and severity of the clinical condition in the AIRE defective individuals. The proposed hypothesis that in APECED, in addition to strong tissue destructive mechanisms, a controlling regulatory mechanism does exist, allow us to conclude that APECED could be treated, and even cured, with immunological manipulation.

Psoriasis in autoimmune polyendocrine syndrome type I: A possible complication or a non-endocrine minor component?

“…This protective effect has been postulated by Kluger et al, who also suggested studies in large cohorts of autoimmune polyendocrine syndrome type I to statistically confirm the same. [13] Thus, psoriasis as a complication or as a non-endocrine minor component of autoimmune polyendocrine syndrome type I may occur in the absence of candidiasis, that is, they may occur only as mutually exclusive phenomena. …”

B Cells Producing Pathogenic Autoantibodies

“…Both diseases are caused by genetic defects affecting T cell development. APECED patients carry mutations in the autoimmune regulator gene (Aire) [163]. Aire functions as a transcriptional regulator that induces the expression of peripheral tissue self-antigens in medullary epithelial cells and DCs in the thymus.…”

Lupus pathobiology based on genomics

“…Recently, it was shown that polymorphisms in ICA1 promoter may alter binding of the transcription factor AIRE , resulting in downregulation of ICA1 expression in medullary thymic epithelial cells leading to loss of immunologic tolerance to this self-antigen and triggering autoimmunity (Bonner et al 2012). Interestingly, mutations in AIRE lead to autoimmune polyendocrinopathy candidiasis ectodermal dystrophy (APECED) in which multiple autoantibodies form against several endocrine organs as well as against IFN, IL17, and IL22 (Kluger et al 2012). APECED does not clinically resemble SLE, pointing to perhaps the significance of IFNs to SLE pathogenesis.…”