Dermal γδ T cells translocate into epidermis under inflammatory conditions. (A and B) In vivo two-photon imaging of Tcrd-GDL Vaseline- (ctrl.) and IMQ-treated ear skin, respectively. Shown are pooled data from three experiments with each one to two mice per group, Student’s t test. (A) Using IMARIS software motile dermal γδ T cells (red dots) were tracked and dermis was defined as surface by second harmonics signal corresponding to collagen (blue, right). Frequency of motile γδ T cells in epidermis (see Video 4), one dot per video (left). (B) Scatter plots show track straightness (displacement length divided by track length, left) and mean track speed (right). (C) Ear skin histology of inflamed Tcrd-H2BeGFP ears (representative image of two different stainings). Mice were treated for five consecutive days with Vaseline (ctrl.) or IMQ-containing cream (Aldara; IMQ). Red: epidermis (keratin 14); green: GFP⁺ γδ T cells below epidermis; purple: GFP⁺ Vγ5⁺ dendritic epidermal T cells (blue Vγ5⁺ cells); yellow: GFP⁺Vγ5^– dermal γδ T cells within epidermis. Bars, 50 µm. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ns, not significant.