Accumulation and activation of epidermal γδ T cells in a mouse model of chronic dermatitis is not required for the inflammatory phenotype

Chronic skin inflammation resulting from a defective epidermal barrier is a hallmark of atopic dermatitis (AD). We previously demonstrated that mice lacking FGF receptors 1 and 2 in keratinocytes (K5-R1/R2 mice) develop an AD-like chronic dermatitis as a result of an impaired epidermal barrier. Here, we show that gamma delta T cells, which rapidly respond to various insults, accumulate in the epidermis of K5-R1/R2 mice before the development of histological abnormalities. Their number and activation further increase as the phenotype progresses, most likely as a consequence of increased expression of Il-2 and Il-7 and the stress-induced proteins Rae-1, H60c, Mult1, PlexinB2, and Skint1. To determine the role of gamma delta T cells in the skin phenotype, we generated quadruple mutant K5-R1/-R2 mice lacking gamma delta T cells. Surprisingly, loss of gamma delta T cells did not or only marginally affect keratinocyte proliferation, epidermal thickness, epidermal barrier function, and accumulation and activation of different immune cells in the skin of K5-R1/R2 mice, possibly due to partial compensation by alpha beta T cells. These results demonstrate that gamma delta T cells do not contribute to the development or maintenance of chronic inflammation in response to a defect in the epidermal barrier.