Dermal γδ T cells – What have we learned?

• Most mouse dermal γδ T cells are IL-17+, CCR6+, motile, and Vγ4Vδ4+ or Vγ6Vδ1+.
• They are pathogenic in psoriasis, but enhance protection against some pathogens.
• They also enhance CD4+ αβ T cell-mediated immunity.
• Human dermal γδ T cells are analogous in producing IL-17 and exacerbating psoriasis.
• Responses by dermal γδ T cells can be triggered without the addition of antigen.

Over the last several years, a number of papers have called attention to a distinct population of γδ T cells preferentially found in the dermis of the skin of normal mice. These cells appear to play an important role in promoting the development of psoriasis, but also are critical for host resistance to particular pathogens. They are characterized by the expression of a limited subset of γδ T cell receptors and a strong propensity to secrete IL-17. Perhaps most importantly, humans appear to carry an equivalent dermal γδ T cell population, likewise biased to secrete IL-17 and also implicated as playing a pathogenic role in psoriasis. This review will attempt to summarize and reconcile recent findings concerning the dermal γδ T cells.