Consistent with the reduced allergic airway inflammation as a result of defective ILC231 and T cell priming described in Tph1−/− mice, we found a decreased susceptibility of Tph1−/− mice to fungal allergy (Fig. S1), a finding pointing to a unique, as yet unappreciated, beneficial role 5-HT may have in acute pneumonia. The gene discussed is TPH1; the disease is pneumonia.