Human skin is protected by four functionally and phenotypically discrete populations of resident and recirculating memory T cells

The skin of an adult human contains about 20 billion memory T cells. Epithelial barrier tissues are infiltrated by a combination of resident and recirculating T cells in mice, but the relative proportions and functional activities of resident versus recirculating T cells have not been evaluated in human skin. We discriminated resident from recirculating T cells in human-engrafted mice and lymphoma patients using alemtuzumab, a medication that depletes recirculating T cells from skin, and then analyzed these T cell populations in healthy human skin. All nonrecirculating resident memory T cells (TRM) expressed CD69, but most were CD4(+), CD103(-), and located in the dermis, in contrast to studies in mice. Both…

• NS
  National Science Foundation
• DR
  Damon Runyon Cancer Research Foundation
• LA
  Leukemia and Lymphoma Society
• BA
  Brigham and Women's Hospital
• UO
  University of Texas Southwestern Medical Center
• SN
  Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung
• NI
  National Institutes of Health
• NI
  National Institute of Mental Health
• NC
  National Cancer Institute

  Awards: P50 CA9368305, CA9368305
• NI
  National Institute of Allergy and Infectious Diseases

  Award: R01 AI097128
• NI
  National Institute of Arthritis and Musculoskeletal and Skin Diseases

  Awards: R01 AR063962, R01 AR056720