Il33 depletion in Ifngr1-/-Rag2-/-Il33gfp/gfp mice markedly suppressed both the spontaneous onset of fibrosis (Fig. 6d, e) and the infiltration of ILC2s in the BALF (Fig. 6f), thereby indicating that IL-33 is indispensable for the development of PF development in Ifngr1-/-Rag2-/- mice. Here, IL33 is linked to pemphigus foliaceus.