MUC5B and Pneumocystis infectious disease: Induction of the CLCA1 pathway with increased mucins has been shown to correlate with Pneumocystis infection in humans (Vargas et al., 2013; Perez F. J. et al., 2014; Rojas et al., 2019) and in animal models (Swain et al., 2012; Eddens et al., 2016; Iturra et al., 2018; Rojas et al., 2019) and is strongly related to IL-13 driven mucus cell metaplasia, STAT6 activation and MUC5AC and MUC5B expression in the airways (Swain et al., 2012; Eddens et al., 2016; Iturra et al., 2018; Rojas et al., 2019).