Mast cell VDR expression helps to limit leukocyte numbers in ear skin exposed to chronic low-dose UVB irradiation. Flow cytometric analysis of granulocytes and macrophages (A and B) and CD4⁺ and CD4⁺CD25⁺ T cells (C and D) 24 h after the last of 15 exposures to 2 kJ/m² UVB irradiation (+ UVB) or at control sites not treated with UVB irradiation (– UVB) in ear skin of WBB6F₁-Kit^+/+ (WT) mice, mast cell–deficient WBB6F₁-Kit^W/W-v (Kit^W/W-v) mice, WT BMCMC→Kit^W/W-v mice, and VDR^−/− BMCMC→Kit^W/W-v mice. Percentage values in A and C refer to percentage of total viable cells present in the depicted section of the plot. (A) Representative FACS plots of granulocytes and macrophages in ears derived from individual mice. (B) Granulocytes (gated population R1, Gr-1^hi; R2, Gr-1⁺) and macrophages (macs; R3 [“activated macrophages”], F4/80⁺ Gr-1^hi; R4, F4/80⁺) recovered per ear. (C) Representative FACS plots of T cell populations in ears derived from individual mice, where live populations of CD3⁺ T cells were first gated and then CD4⁺CD25⁺CD62L⁻ T cells were selected, and where 4% paraformaldehyde-fixed CD4⁺ T cells were gated, and then CD25⁺ FoxP3⁺ T cells were selected. Percentages of gated T cell populations indicated are the percentage of the total cell population in that ear. (D) CD4⁺ T cell populations recovered per ear based on flow cytometric analysis of fixed cells (for CD4⁺CD25⁺FoxP3⁺ T cells) or live cells (the other three groups). (B and D) Data (n = 6–12 per group) are of mean values from 3 different experiments, each of which gave similar results, in which individual ears of three to four mice per group were analyzed in each experiment. *, P < 0.05; **, P < 0.01; ***, P < 0.001 for the indicated comparisons.