Figure 2.

Mast cell VDR expression helps to limit tissue swelling associated with chronic low-dose UVB irradiation. (A) Ear swelling after 15 exposures to 2 kJ/m² of UVB (each arrowhead indicates a single exposure) in WT WBB6F₁-Kit^+/+ mice (black diamond, Kit^+/+; n = 11), mast cell–deficient WBB6F₁-Kit^W/W-v mice (open diamond, Kit^W/W-v; n = 9), and WBB6F₁-Kit^W/W-v mice engrafted in the ear pinnae with WT C57BL/6-VDR^+/+ BMCMCs (light gray diamond, WT BMCMC→Kit^W/W-v, n = 9) or VDR^−/− BMCMCs (dark gray circle, VDR^−/− BMCMC→Kit^W/W-v; n = 12). ***, P < 0.0001 for the indicated comparisons between groups of UVB-irradiated mice. Data (n = 9–12 per group) are from the three independent experiments performed (each with three to four mice per group), each of which gave similar results. Ear swelling measurements in ears not irradiated with UVB (“no UVB”) are highly overlapping for the four groups of mice; for each group, responses in UVB-irradiated ears were significantly different from those in the non-UVB–irradiated ears at P < 0.0001. (B) Numbers of dermal mast cells in ear pinnae after 15 exposures to 2 kJ/m² of UVB. *, P < 0.05; **, P < 0.01; ***, P < 0.001; or ****, P < 0.0001, for the indicated comparisons. Data (3–12 mice per group) are from the three experiments performed, each of which gave similar results; each experiment analyzed one ear from a mouse not treated with UVB (– UVB) and single ears from three to four UVB-treated (+ UVB) mice.