Abstract
Autoimmune-polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is a primary immunodeficiency caused by mutations in the autoimmune regulator gene (AIRE). Patients with AIRE mutations are susceptible to Candida albicans infection and present with autoimmune disorders. We previously demonstrated that cytoplasmic AIRE regulates the Syk-dependent Dectin-1 pathway. In this study, we further evaluated direct contact with fungal elements, synapse formation, and the response of macrophage-like THP-1 cells to C. albicans hyphae to determine the role of AIRE upon Dectin receptors function and signaling. We examined the fungal synapse (FS) formation in wild-type and AIRE-knockdown THP-1 cells differentiated to macrophages, as well as monocyte-derived macrophages from APECED patients. We evaluated Dectin-2 receptor signaling, phagocytosis, and cytokine secretion upon hyphal stimulation. AIRE co-localized with Dectin-2 and Syk at the FS upon hyphal stimulation of macrophage-like THP-1 cells. AIRE-knockdown macrophage-like THP-1 cells exhibited less Dectin-1 and Dectin-2 receptors accumulation, decreased signaling pathway activity at the FS, lower C. albicans phagocytosis, and less lysosome formation. Furthermore, IL-1β, IL-6, or TNF-α secretion by AIRE-knockdown macrophage-like THP-1 cells and AIRE-deficient patient macrophages was decreased compared to control cells. Our results suggest that AIRE modulates the FS formation and hyphal recognition and help to orchestrate an effective immune response against C. albicans.
Highlights
Immunocompromised patients affected by fungal infections experience high morbidity and mortality
The myelomonocytic THP-1 cell line was cultured in RPMI 1640 supplemented with 10% inactivated fetal bovine serum, 2 mM l-glutamine, 10 U/mL penicillin, 100 μg/mL streptomycin, 10 mM HEPES, 2 mM sodium pyruvate, and 100 μM MEM nonessential amino acids, in a humid 5% CO2 atmosphere at 37°C. 2.5 × 106 THP-1 cells were differentiated to macrophage-like THP-1 cells using 100 U/mL IFN-γ and 1000 U/mL TNF-α for 24–48 h in 6-well plates, following overnight resting in RPMI media
To evaluate the fungal synapse (FS) formation, macrophage-like THP-1 cells were stimulated with C. albicans hyphae for 10, 20, or 30 min (Figure 1A)
Summary
Immunocompromised patients affected by fungal infections experience high morbidity and mortality. Gainof-function (GOF) mutations in signal transducer and activator of transcription 1 (STAT1) impair dephosphorylation of STAT1 in response to IFN-γ, IFN-α/β, and IL-27 stimulation. This leads to defects of IL-17-producing T cells, and many of these patients develop severe CMC [5, 13]. The Y238X polymorphism in Dectin-1 do not result in immune deficiencies but it increases predisposition to fungal infections due to low production of cytokines by innate immune cells and a functional defect in T helper (TH) 17 responses [15, 16]. Patients with autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) may present with high titers of neutralizing autoantibodies against IL-17A, IL-17F, and IL-22 and subsequent CMC [17, 18]
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