CFTR and infection: Correlations between the levels of CFTR expression, HCO3− secretion, and host defense [29,38] have been demonstrated in the lungs and support that HCO3− is an essential component of the ASL to maintain a normal ASL pH of ~7.1 [18,23] and promote a competent innate immunity, such as antimicrobial activity, in order to protect the lungs against infections.