Capturing the tissue-resident CD1a-reactive T cell population from human skin — ASN Events
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  3. Capturing the tissue-resident CD1a-reactive T cell population from human skin

Capturing the tissue-resident CD1a-reactive T cell population from human skin (#184)

Rachel Cotton 1 2 , Tan-Yun Cheng 2 , Ildiko Van Rhijn 2 , Rachael A Clark 1 3 , Branch Moody 1 2
  1. Harvard University, Cambridge, MA, United States
  2. Division of Rheumatology, Immunology and Allergy, Brigham and Women's Hospital, Boston, MA, USA
  3. Department of Dermatology, Brigham and Women's Hospital, Boston, MA, USA

CD1a-reactive T cells bind CD1a without directly contacting the cargo in the CD1a pocket. Altered-self lipids, environmental lipids, or small molecules in CD1a fine-tune the activation of these T cells by interfering with or permitting CD1a-TCR contacts. The CD1a system in humans is uniquely concentrated in skin: CD1a has constitutively high surface expression on epidermal Langerhans cells; epidermal lipids are permissive for CD1a-TCR binding; and CD1a-reactive T cells in circulation have a skin-homing Th22-like signature. Studies from our group and others implicate CD1a-autoreactive T cells in allergic and inflammatory skin diseases. However, capturing CD1a-reactive T cells from their tissue microenvironment remains a major gap. There are no known surface markers or TCR gene patterns to discriminate CD1a-reactive cells from other skin-resident T cells. To obtain skin T cells from healthy individuals, we cultured discarded skin from cosmetic surgeries on 3D matrices with IL-2 and IL-15, recovering millions of T cells migrating from the skin per donor. To enrich CD1a-dependent responses, we co-cultured skin T cells with in vitro derived CD1a++ Langerhans’-like cells. We measured the frequency of CD1a-depdendent cells based on IL-22 production in activation assays with CD1a+ K562 cells +/- CD1a-blocking antibody. By IL-22 ELISPOT, CD1a-dependent responses across donors (n=13) were variable, with 7/13 exhibiting CD1a-dose-dependent and blockable numbers of CD1a-dependent IL-22-producing cells. A second group (3/13) had an elevated frequency in IL-22-producing T cells at baseline that was CD1a-dose dependent but only partially reduced by CD1a-blocking, suggesting that CD1a-reactive T cells make up a variable fraction of IL-22+ skin T cells by donor. Using a newly developed IL-22 capture reagent, we are positively selecting CD1a-dependent IL-22-secreting cells for further phenotyping and high throughput sequencing of TCRα/δ and TCRβ genes. By adapting a described 3D culture method for skin, we are capturing CD1a-reactive T cells from their tissue microenvironment.