Treatment of WT mice with the BTKi ibrutinib or acalabrutinib — a second-generation BTKi that features greater selectivity for BTK and lacks ITK or TEC targeting (18, 30) — phenocopied the increased susceptibility to pulmonary aspergillosis observed in Btk–/– mice (Figure 1, A, F, and G). Here, BTK is linked to aspergillosis.