Platelet-Sourced TGF-β Promotes Th17 Responses and Enhances Airway Neutrophilia

Microbial, especially fungal, sensitization has been associated with the development and exacerbation of treatment-refractory neutrophilic asthma. Among the airway-inhabiting fungi, <i>Aspergillus fumigatus</i> and <i>Candida albicans</i> are the dominant species that elicit protective T helper (Th) 17 and other T cell responses, contributing to airway neutrophilia and steroid resistance. However, it is not fully understood how fungal airway colonization impacts the immunopathogenesis of asthma. Here, we used a neutrophilic asthma model induced by <i>C. albicans</i> to study the immune regulation of this disease. We found that intranasal administration of <i>C. albicans</i> induced platelet infiltration into the lung. Platelet-expressed latent TGF-β could be activated specifically by Th17 cells and drive the commitment, maintenance, and expansion of Th17 cells. In Candida-induced asthma, an adoptive transfer of platelets enhanced Th17 responses, increasing airway neutrophil influx. Thus, managing airway mycobiota and reducing platelet intrapulmonary infiltration may serve as a promising interventional approach.