Stress-Induced Chemokine Production by Hair Follicles Recruits Dendritic Cells to Sites of Minor Trauma

The study demonstrated that hair follicles (HF) played a crucial role in recruiting Langerhans cells (LC) to sites of minor trauma in the epidermis. Using Lysozyme M-Cre mice and bone marrow transplantation experiments, researchers found that immediate LC precursors (pre-LC) derived from Gr-1hi monocytes infiltrated the epidermis through HF in a CCR2/CCR6-dependent manner. Different subsets of HF keratinocytes expressed specific chemokines, with the infundibulum expressing CCL2, the isthmus expressing CCL20, and the bulge producing CCL8. This differential chemokine production facilitated or inhibited LC recruitment. The findings were supported by skin graft experiments on nude mice, showing that pre-LC repopulated hair-bearing but not hairless skin. The study suggested that HF serve as portals for immune cell trafficking during skin inflammation, with potential similar mechanisms in non-hair-bearing epithelium.