Human epidermal resident memory T cells: beyond the dermal perspective

Area of Science:

• Immunology
• Dermatology
• Cell Biology

Background:

• The epidermis was traditionally viewed as a physical barrier, with skin immune research focused on the dermis.
• Recent findings reveal the epidermis harbors significant populations of resident T cells, including conventional and regulatory T_RM cells.

Purpose of the Study:

• To review current knowledge on human epidermal T_RM cells, focusing on their origin, composition, phenotype, and dynamics.
• To highlight the epidermis as a specialized immunological compartment.

Main Methods:

• Review of existing literature and studies on human skin tissues.
• Analysis of T_RM cell populations, including CD8+, CD69+, CD103+, CD49a, and CD101 expression.
• Examination of interactions with Langerhans cells and keratinocytes.

Main Results:

• Epidermal T_RM cells are characterized by CD8+CD69+CD103+ phenotypes, with cytotoxic subsets expressing CD49a and CD101.
• Regulatory T_RM cells form a distinct network promoting immune tolerance.
• Epidermal T_RM cells actively patrol, interact with Langerhans cells, and maintain epidermal immune homeostasis.

Conclusions:

• The epidermis is an autonomous immunological compartment, not just a barrier.
• Epidermal T_RM cells, Langerhans cells, and keratinocytes form an integrated immune ecosystem.
• Understanding epidermal immunity offers insights into skin diseases like HIV, vitiligo, and alopecia areata.