A fungal antigenic driver for Löfgren's syndrome sarcoidosis.

Löfgren's syndrome is an acute form of sarcoidosis that is characterized by the activation of CD4+ T helper cells. In this issue of JEM, Greaves et al. (2021. J. Exp. Med.https://doi.org/10.1084/jem.20210785) identified a peptide derived from an airborne mold species that stimulates T cells of Löfgren's syndrome patients in an HLA-DR3-restricted manner. An increased serum IgG antibody response to the full-length protein was also observed in those patients, indicating that the fungus Aspergillus nidulans might be the elusive microbial agent that drives acute sarcoidosis.