Hair follicles act as portals for the recruitment of Langerhans cells, immune cells of the skin and mucosa, to the epidermis, according to a study published in Nature Immunology.

Hair follicles contribute to hair growth, sebaceous secretions and act as reservoirs for various stem cells of the epidermis. Langerhans cells are distributed in a dense network in the epidermis, where they self-renew in normal conditions, but are replenished by cells in the bone marrow under stress conditions.

Nagao and colleagues show that following stress or inflammatory stimuli, distinct regions of the hair follicle secrete soluble mediators known as chemokines, which are able to direct the migration of Langerhans cell progenitors into the epidermis. Correlating with these observations, Langerhans cells are lacking in the skin of patients suffering from lichen planopilaris, an autoimmune condition that leads to destruction of the hair follicles.