Dermal γδ T Cells Do Not Freely Re-Circulate Out of Skin and Produce IL-17 to Promote Neutrophil Infiltration during Primary Contact Hypersensitivity

PLoS One. 2017 Jan 12;12(1):e0169397. doi: 10.1371/journal.pone.0169397. eCollection 2017.

Abstract

The role of mouse dermal γδ T cells in inflammatory skin disorders and host defense has been studied extensively. It is known that dendritic epidermal T cells (DETC) have a monomorphic γδ T cell receptor (TCR) and reside in murine epidermis from birth. We asked if dermal γδ cells freely re-circulated out of skin, or behaved more like dermal resident memory T cells (TRM) in mice. We found that, unlike epidermal γδ T cells (DETC), dermal γδ cells are not homogeneous with regard to TCR, express the tissue resident T cell markers CD69 and CD103, bear skin homing receptors, and produce IL-17 and IL-22. We created GFP+: GFP- parabiotic mice and found that dermal γδ T cells re-circulate very slowly-more rapidly than authentic αβ TCR TRM, but more slowly than the recently described dermal αβ TCR T migratory memory cells (TMM). Mice lacking the TCR δ gene (δ-/-) had a significant reduction of 2,4-dinitrofluorobenzene (DNFB)-induced contact hypersensitivity (CHS). We created mice deficient in dermal γδ T cells but not DETC, and these mice also showed a markedly reduced CHS response after DNFB challenge. The infiltration of effector T cells during CHS was not reduced in dermal γδ T cell-deficient mice; however, infiltration of Gr-1+CD11b+ neutrophils, as well as ear swelling, was reduced significantly. We next depleted Gr-1+ neutrophils in vivo, and demonstrated that neutrophils are required for ear swelling, the accepted metric for a CHS response. Depletion of IL-17-producing dermal Vγ4+ cells and neutralization of IL-17 in vivo, respectively, also led to a significantly reduced CHS response and diminished neutrophil infiltration. Our findings here suggest that dermal γδ T cells have an intermediate phenotype of T cell residence, and play an important role in primary CHS through producing IL-17 to promote neutrophil infiltration.

MeSH terms

  • Animals
  • Dermatitis, Contact / genetics
  • Dermatitis, Contact / immunology*
  • Dermatitis, Contact / pathology
  • Dermis / immunology*
  • Dermis / pathology
  • Interleukin-17 / genetics
  • Interleukin-17 / immunology*
  • Interleukin-22
  • Interleukins / genetics
  • Interleukins / immunology
  • Mice
  • Mice, Knockout
  • Neutrophil Infiltration*
  • Neutrophils / immunology*
  • Neutrophils / pathology
  • Receptors, Antigen, T-Cell, gamma-delta / genetics
  • Receptors, Antigen, T-Cell, gamma-delta / immunology*
  • T-Lymphocytes / immunology*
  • T-Lymphocytes / pathology

Substances

  • Interleukin-17
  • Interleukins
  • Receptors, Antigen, T-Cell, gamma-delta