Langerhans cells in innate defense against pathogens.

Langerhans cells (LCs) are at the frontline in defense against mucosal infections because they line the mucosal tissues and are ideally situated to intercept pathogens. Recent data suggest that LCs have an innate anti-HIV-1 function. LCs express the LC-specific C-type lectin Langerin that efficiently captures HIV-1, which prevents HIV-1 transmission. However, immune activation of LCs changes these protective cells into HIV-1-transmitting cells, which indicates that the antiviral function of LCs depends on several factors including co-infections. In this review, we discuss the dual role of LCs in innate defense against pathogens, with a focus on HIV-1 dissemination.