Treatment of RORγt diphtheria toxin receptor (DTR) newborn mice (Rorc Cre mice crossed with Rosa26-iDTR mice; RorγtiDTR) with DT diminished the number of ILC3s in the lungs and reduced IL-22 in bronchial lavage fluid (BAL), making them more susceptible to pneumonia. Here, IL22 is linked to susceptibility to pneumonia measurement.