Figure 5.

Effect of UV on skin-infiltrating T cells. (A) Mice were exposed or not to UV radiation as described in Materials and methods and, 1 h later, skin sections were obtained and immunostained for CD3 (not depicted) and dual phospho-p38 (pT180/pY182). Phospho-p38–positive T cells are indicated with arrowheads, keratinocytes with arrows, and dermal fibroblasts with asterisks. Bars: 200 µm (left); 100 µm(right). Data are representative of five mice per group from two independent experiments. (B) Purified CD4⁺ T cells from the skin of UV treated or untreated mice were stimulated in vitro with anti-CD3/CD28 for 24 h, and Irf4 mRNA expression was measured by real-time PCR. Results are the mean ± SEM of two independent experiments with a total of 5 mice per group. *, P < 0.05, NS, not statistically significant (unpaired two-tailed Student’s t test). (C) Immunohistochemical staining of human psoriatic skin lesions with anti-CD3 or phospho-p38 Y323 (p38 pY323)-specific antibodies. The insets in the middle pane show the T cell–poor and T cell–rich areas that are enlarged in the left and right panes for CD3 and the top and bottom panes for p38 pY323. Arrows indicate examples of p38 pY323-positive cells (n = 3 patients; Bars: 1 mm (middle); 50 µm (outer panels). (D) Immunofluorescence staining for p38 pY323 (cyan), IRF4 (green), IL-17A (red), and the corresponding isotype control of representative psoriatic skin lesions biopsies before and after UVB treatment (Bar, 100 µm). (E) Quantitation of p38 pY323⁺ cells that are also positive for IRF4 and IL-17A (triple positive) in the skin of 6 patients before treatment and 3 of these after UVB treatment. *, P < 0.05. NS, not significant (unpaired two-tailed Student’s t test).