Figure 5. IL-34 Is Not Critical for the Repopulation of LCs in Inflammation but for Their Maintenance.

(A and B) Il34^LacZ/LacZ and Il34^LacZ/+ mice were exposed to UV light. (A) Plots show the percentage and total cell number (±SEM) of monocytes (CD11b⁺Ly6C⁺) among ear skin cell suspensions (CD45⁺ Ly6G⁻) and of LCs (Epcam⁺Langerin⁺) among CD45⁺ epidermal cells 7 days (d) after UV treatment or in untreated control mice (n = 4 for UV-treated groups and n = 3 for untreated control mice). Data are pooled from two individual experiments. *p < 0.05, **p < 0.01, ***p < 0.001 (Student's t test, unpaired). (B) Plots show the percentage and total cell number (±SEM) of LCs (Epcam⁺Langerin⁺) among CD45⁺ epidermal cells on day 21 (n = 7), day 45 (n = 7) and day 90 (n = 5) after UV exposure. Pooled data of two individual experiments. *p < 0.05, **p < 0.01, ***p < 0.001 (Student's t test, unpaired). (C) Quantitative RT-PCR analysis of Il34 and Csf1 mRNA levels in the epidermis of UV exposed WT mice at different time points post UV exposure or in naive WT mice (d 0). Data were normalized to the expression of RNA polymerase 2 (n = 3 for d 7, d 21 and d 42, n = 2 for d 0).

(D and E) Il34^LacZ/LacZ and Il34^LacZ/+ mice were treated with Calcipotriol (CP) for 2 weeks and epidermal cells were analyzed 21 days post treatment. (D) Plots show the percentage of LCs among CD45⁺ epidermal cells. Graph displays the total cell number (±SEM) of LCs of CP-treated mice (n = 6). Pooled data of two individual experiments are shown. (E) Images depict anti-MHCII staining on ear-derived epidermal sheets of Il34^LacZ/LacZ and Il34^LacZ/+ mice 21 days after CP treatment (scale bar represents 100 μm).

(F and G) Ears of Il34^LacZ/LacZ and Il34^LacZ/+ mice were treated with Aldara cream for 9 days (n = 4). Shown is one representative of two individual experiments. (F) Kinetics of Aldara-induced skin inflammation measured by increase in ear thickness. (G) Plots show the percentage and total cell number (±SEM) of LCs among CD45⁺ epidermal cells of Aldara treated ears on day 12 (n = 7). *p < 0.05, **p < 0.01, ***p < 0.001 (Student's t test, unpaired).