BTK and aspergillosis: Thus, we focused our studies on the role of BTK in neutrophils, as these cells are the principal effectors against Aspergillus (2) and because we found that Btk-deficient mice, as well as mice with myeloid phagocyte-specific and neutrophil-specific Btk ablation, were susceptible to aspergillosis, indicating that BTK plays a critical role in promoting neutrophil-mediated defense against this fungal infection.