Pathogenic CD8 + Epidermis-Resident Memory T Cells Displace Dendritic Epidermal T Cells in Allergic Dermatitis.

The skin is our interface with the outside world, and consequently it is exposed to a wide range of microbes and allergens. Recent studies have indicated that allergen-specific skin-resident memory T (T _RM ) cells play a role in allergic contact dermatitis (ACD). However, the composition and dynamics of the epidermal T-cell subsets during ACD are not known. Here we show that exposure of the skin to the experimental contact allergen DNFB results in a displacement of the normally occurring dendritic epidermal T cells (DETC) concomitant with an accumulation of epidermal CD8 ⁺ CD69 ⁺ CD103 ⁺ T _RM cells in mice. By studying knockout mice, we provide evidence that CD8 ⁺ T cells are required for the displacement of the DETC and that DETC are not required for recruitment of CD8 ⁺ T _RM cells to the epidermis following allergen exposure. We demonstrate that the magnitude of the allergic reaction correlates with the number of CD8 ⁺ epidermal T _RM cells, which again correlates with allergen dose and number of allergen exposures. Finally, in an attempt to elucidate why CD8 ⁺ epidermal T _RM cells persist in the epidermis, we show that CD8 ⁺ epidermal T _RM cells have a higher proliferative capability and are bioenergetically more stable, displaying a higher spare respiratory capacity than DETC.
(Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)