Figure 4.

Cyclooxygenase (COX)-2–derived prostaglandins (PGs) inhibit T helper cell type 9 (Th9) differentiation through down-regulation of IL-17RB. (A) Naive CD4⁺ T cells from COX-2^+/+ and COX-2^−/− mice were differentiated into Th9 cells and IL-17RB mRNA levels were assayed by real-time RT-PCR. (B and C) The effects of PGD₂, PGE₂, PGF_2α, and PGI₂ (1 μM each) on IL-25 and IL-17RB levels was examined by RT-PCR and real-time RT-PCR (n = 5; *P < 0.05 versus vehicle). (D) Naive CD4⁺ T cells from wild-type (WT) mice were transfected with IL-17RB receptor siRNAs or control siRNA. Transfected cells were then differentiated in the presence of anti-CD3, anti-CD28, anti–INF-γ, IL-4, and transforming growth factor (TGF)-β for 5 days. Levels of IL-9 and IL-17RB relative to GAPDH were determined by real-time RT-PCR (n = 3; *P < 0.05 versus control siRNA). (E) WT mice were sensitized and exposed to ovalbumin (OVA), after which lung CD4⁺ T cells were isolated and levels of IL-9, IL-10, and IL-17RB mRNAs were determined by real-time RT-PCR. (F) Levels of IL-17RB in allergic COX-2^−/− and WT mice by real-time RT-PCR. (G) Immunofluorence staining of lungs from COX-2^+/+ and COX-2^−/− mice with anti–CD4⁺-phycoerythrin, anti–IL-17RB–fluorescein isothiocyanate and anti–IL-9–antigen-presenting cells after OVA exposure. IL-17RB-positive Th9 cells are increased in inflammatory loci of COX-2^−/− lungs. Scale bars = 50 μm. GAPDH = glyceraldehyde-3-phosphate dehydrogenase.