Figure 1.

Systemic low-dose UVB impedes primary ova-specific CD8 T-cell (Tc) responses and DTH independently of regulatory CD4⁺CD25⁺ T-cell activation. A: Mice were irradiated with 150 mJ/cm² UVB daily for 3 days on the dorsum and then s.c. immunized with 200 μg ova and 40 μg saponin in saline on the abdomen 3 days after the last irradiation. Seven days after immunization, ova-specific CD8 T cells in the spleen were examined by SIINFEKL-tetramer (Tet) staining. Representative dot plots of activated CD44hi Tet-positive CD8 T cells are gated on CD8⁺ β T-cell receptor–positive T cells from immunized unirradiated (NoUV) and UV-irradiated mice. The total splenic number and the percentage of CD44hi ova-specific CD8 T cells of total CD8 T cells are presented. B: On day 7 after immunization, mice were injected with SIINFEKL–CFSE-lo– and irrelevant–CFSE-hi–labeled cells, and the extent of in vivo cytotoxic killing was determined from spleens at 4 hours after injection. Representative histograms from NoUV and UV-irradiated mice are shown. The percentage-specific lysis from in vivo cytotoxic killing is presented. CFSE, carboxyfluorescein diacetate, succinimidyl ester. C: On day 7 after immunization, mice were challenged with ova intradermally in the ear skin; and the DTH reaction was determined at 24-hour intervals for 5 days after challenge. The increase in ear thickness is shown in NoUV and UV-irradiated mice after controlling for nonspecific increases due to the injection in unimmunized mice. D: CD4⁺CD25⁺ cells were isolated from the sDLNs of donor mice that had been irradiated with 150 mJ/cm² UVB daily for 3 days on the dorsum and immunized. Cells, 0.5 × 10⁶, were adoptively transferred into naïve mice i.v.; the next day, recipient mice were immunized with ova. Seven days after immunization, SIINFEKL-Tet–positive cells were examined in the spleens. The total number and the percentage of CD44hi Tet–positive cells of CD8 T cells are presented in mice that were not transferred and in mice that were transferred with cells from NoUV or UV-irradiated donors. E: The percentage-specific lysis from an in vivo cytotoxic killing assay at 7 days after immunization in transferred and not transferred mice. F: The DTH reaction at 7 days after immunization in NoUV, UV irradiated and not transferred (UV), transferred with cells from unirradiated donors (TNoUV), and transferred with cells from UV-irradiated donors (TUV) mice. Data represent a pool of three to four repeat experiments (n = 9 to 12 mice per group) and are given as mean ± SEM. Comparisons between not transferred UV-irradiated and unirradiated are shown. *P < 0.05, **P < 0.01, and ***P < 0.001.