The dual roles of fungi: allergens and pathogens

OpenAlex İngilizce

Fungal infections and hypersensitivity represent two distinct yet interconnected host immune responses. While infection primarily activates innate immune pathways to combat pathogens and opportunists, hypersensitivity arises from exaggerated immune responses to fungal allergens. This duality highlights the complex balance between immune defence against infection and the risk of an inappropriate hypersensitivity response to fungal antigens. Allergens elicit allergic reactions in the respiratory system, skin, and gastrointestinal tract. Inhalation of airborne propagules from e.g., Aspergillus, Alternaria, and Penicillium species frequently leads to respiratory disorders like allergic rhinitis, allergic fungal rhinosinusitis, allergic asthma, or allergic bronchopulmonary aspergillosis / mycosis. Cutaneous exposure to allergens such as Trichophyton may provoke Id reactions, and Malassezia and Candida exacerbate atopic dermatitis or induce urticaria. Furthermore, fungal antigens may interact with the gut-associated immune system, potentially triggering or aggravating food allergies. Antibody- and T-cell-mediated hypersensitivity responses are central to these pathophysiological processes, with environmental influences and genetic predispositions modulating the intensity of allergic manifestations, especially in predisposed individuals. Despite the high prevalence of fungus-induced allergic diseases, precise diagnosis remains challenging due to the vast heterogeneity of extant species and antigenic cross-reactivity. Conventional diagnostic tools, such as skin prick tests and serum total or specific IgE assays are limited by the lack of standardized extracts and variability in antigenic specificity. The dual role of fungal exposure in infection and hypersensitivity underscores the need to deepen our understanding of the immunopathological mechanisms underlying microbial sensitization, identify specific allergens, and elucidate the molecular pathways involved. These areas are essential for enhancing diagnostic accuracy and developing standardized allergen extracts, thereby facilitating the management and treatment of allergic conditions.