An intermediate activation state primes Langerhans cell migration from the epidermis.

Area of Science:

• Immunology
• Dermatology
• Cell Biology

Background:

• Langerhans cells (LCs) are key immune cells in the epidermis, acting as sentinels against environmental threats and skin damage.
• Despite their importance, the precise immunological and physiological functions of LCs, especially during activation and migration, are not fully understood.

Purpose of the Study:

• To elucidate the activation trajectory and migration dynamics of epidermal Langerhans cells.
• To identify novel subpopulations and molecular mechanisms governing LC responses to skin injury.

Main Methods:

• Single-cell transcriptomic analysis of over 22,000 epidermal LCs under homeostatic and injured conditions.
• Intravital imaging to observe LC behavior in vivo.
• Integration with external datasets and analysis of C3-deficient mice models.

Main Results:

• Defined sequential activation stages of LCs, revealing a distinct intermediate state prior to migration.
• Identified a novel population of activated LCs expressing complement system components and receptors.
• Demonstrated that fibroblasts are a major source of C3, which is essential for effective LC recruitment to wound sites.

Conclusions:

• Uncovered a previously unrecognized population of activated epidermal LCs.
• Highlighted the critical role of complement signaling, specifically C3, in mediating LC recruitment during skin injury.
• Established a novel link between fibroblast-derived C3 and LC function in skin repair.