IL-17/Th17 in anti-fungal immunity: what's new?

How the immune system tailors protective responses to suit the infectious challenge while limiting damage to the host is an emerging theme in T-cell biology. Although many studies have focused on the pathological aspects of IL-17-producing T cells in many autoimmune diseases, their role in protective anti-microbial immunity has also been increasingly recognized. This increased recognition also applies to their role in anti-fungal immunity; however, the role of IL-17-producing T cells in protection versus pathology in fungal infections is still controversial. Although both positive and negative effects on immune resistance have been attributed to the IL-23/Th17 axis in experimental models of fungal infections, defective Th17 cell differentiation has been linked to recurrent pneumonia by filamentous fungi and the occurrence of mucocutaneous candidiasis in patients with primary immunodeficiencies. Here we discuss how recent findings in experimental candidiasis and aspergillosis shed new lights on the contribution of Th17 cells to resistance and pathology to fungi.