WAPing out pathogens and disease in the mucosa: roles for SLPI and Trappin-2

The interface between the external environment and the body’s internal structures is defined by the mucosal tissue and the viscous lining fluid that is responsible for maintaining its integrity and protecting internal structures from damage or infection. Human mucosal fluids include seminal fluid, cervical mucus, bronchial and nasal secretions and tears whose composition is particularly complicated. This review will focus on just two related molecules that are present in the mucosal lining fluid, namely, trappin-2 and secretory leucocyte protease inhibitor (SLPI), that are responsible for many of the homeostatic and host defence functions of these uniquely situated viscous sols. This review will focus on our increasing understanding of these two molecules from a simple role as local antibiotics that respond to pathogen invasion to major orchestrators of cellular interplays, host defence mechanisms and immune homeostasis