Conditional Deletion of TGF-βR1 Using Langerin-Cre Mice Results in Langerhans Cell Deficiency and Reduced Contact Hypersensitivity

Abstract

The critical role of Langerhans cells (LC) in contact hypersensitivity (CHS) was recently questioned in studies using different LC-depletion mouse models. On one hand, inducible ablation of LC led to diminished ear swelling, suggesting functional redundancy between LC and (Langerin+) dermal dendritic cells (DC). On the other hand, constitutive or acute depletion of LC resulted in an enhanced reaction, supporting a regulatory role of LC in CHS. To address this controversy by conditional gene targeting, we generated Langerin-Cre knockin mice. Breeding these mice to a Cre-reporter strain demonstrated robust and specific DNA recombination in LC, as well as other Langerin+ tissue DC. In agreement with the vital requirement of TGF-β signaling for LC development, crossing Langerin-Cre to mice homozygous for a loxP-flanked TGF-βR1 allele resulted in permanent LC deficiency, whereas the homeostasis of dermal Langerin+ DC was unaffected. In the absence of LC, induction of CHS in these Langerin+ DC-specific TGF-βR1–deficient mice elicited decreased ear swelling compared with controls. This novel approach provided further evidence against a regulatory function of LC in CHS. Moreover, these Langerin-Cre mice represent a unique and powerful tool to dissect the role and molecular control of Langerin+ DC populations beyond LC.