Figure 6. see also Figure S5. MCs in the bladder promote Il10 expression.

(A) A whole mount picture of the luminal side of a murine bladder, showing the abundance of MCs (red, avidin-TRITC stained) under the epithelium. (B) Wsh mice, even at basal levels, have lower expression of Il10 in the bladder as compared to WT bladders, determined by real time PCR. (C) With infection, at 6h after bacterial instillation, Il10 expression increases in bladders of WT but not Wsh mice. (D) Il10 is expressed at higher basal levels in the kidneys of Wsh compared to WT mice, as determined by real time PCR. (E) However, upon infection, the high Il10 levels of expression in Wsh kidneys drop dramatically to be not significantly different from those of WT kidneys at 6h. (F) Image shows a bladder section stained for MCs (MMCP6, green), and for IL-10 (red) 24h after UPEC infection. (G) Intracellular staining for IL-10 reveals IL-10⁺ cells in the bladder 24h p.i. Though Treg cells (foxp3⁺CD4⁺) and macrophages (MHC-II⁺CD11b⁺) contribute to the IL-10 in the bladder, the majority of cells that are IL-10⁺ are MCs (ckit⁺). (H) Rescue of increased Il10 expression is seen in infected bladders of Wsh mice reconstituted with WT BMMCs but not Il10^-/- BMMCs at 24h p.i. (I) Wsh mice reconstituted with WT BMMCs have significantly greater activated DCs draining to the RLNs, compared to ILNs 24h p.i. Reconstitution with BMMC from Il10^-/- mice results in comparable numbers of activated DCs in both LNs. *p<0.05, **p ≤0.01, ***p≤0.001; data are representative of ≥3 independent experiments with n≥3. Error bars represent ±SEM. (J) Mcpt5-Cre Il10Fl mice showed the same phenotype as Il10^-/- mice and Il10^-/- BMMC-reconstituted Wsh mice: significantly greater numbers of mature DCs present in both ILN and RLN as compared to WT ILN 24h p.i. (K) Serum UPEC-specific IgG was detected in Mcpt5-Cre Il10Fl mice 7d p.i. Error bars represent the 95% confidence level with n=5.