These authors showed that cysteine protease activity initiates and drives allergic responses and that activation with L-cysteine leads to a significant increase in the induction of IgE and IgG, eosinophilia, interleukin (IL)-4, IL-5, and IL-10 in mouse bronchoalveolar lavage fluid after papain challenge 19. Here, CTSB is linked to Increased total eosinophil count.