Although interleukin (IL) 17 has been extensively characterized, the function of IL-17F, which has an expression pattern regulated similarly to IL-17, is poorly understood. We show that like IL-17, IL-17F regulates proinflammatory gene expression in vitro, and this requires IL-17 receptor A, tumor necrosis factor receptor–associated factor 6, and Act1. In vivo, overexpression of IL-17F in lung epithelium led to infiltration of lymphocytes and macrophages and mucus hyperplasia, similar to observations made in IL-17 transgenic mice. To further understand the function of IL-17F, we generated and analyzed mice deficient in IL-17F or IL-17. IL-17, but not IL-17F, was required for the initiation of experimental autoimmune encephalomyelitis. Mice deficient in IL-17F, but not IL-17, had defective airway neutrophilia in response to allergen challenge. Moreover, in an asthma model, although IL-17 deficiency reduced T helper type 2 responses, IL-17F–deficient mice displayed enhanced type 2 cytokine production and eosinophil function. In addition, IL-17F deficiency resulted in reduced colitis caused by dextran sulfate sodium, whereas IL-17 knockout mice developed more severe disease. Our results thus demonstrate that IL-17F is an important regulator of inflammatory responses that seems to function differently than IL-17 in immune responses and diseases.

We examined the role of the antiapoptotic molecule Bcl-2 in combating the proapoptotic molecule Bim in control of naive and memory T cell homeostasis using Bcl-2−/− mice that were additionally deficient in one or both alleles of Bim. Naive T cells were significantly decreased in Bim+/−Bcl-2−/− mice, but were largely restored in Bim−/−Bcl-2−/− mice. Similarly, a synthetic Bcl-2 inhibitor killed wild-type, but not Bim−/−, T cells. Further, T cells from Bim+/−Bcl-2−/− mice died rapidly ex vivo and were refractory to cytokine-driven survival in vitro. In vivo, naive CD8+ T cells required Bcl-2 to combat Bim to maintain peripheral survival, whereas naive CD4+ T cells did not. In contrast, Bim+/−Bcl-2−/− mice generated relatively normal numbers of memory T cells after lymphocytic choriomeningitis virus infection. Accumulation of memory T cells in Bim+/−Bcl-2−/− mice was likely caused by their increased proliferative renewal because of the lymphopenic environment of the mice. Collectively, these data demonstrate a critical role for a balance between Bim and Bcl-2 in controlling homeostasis of naive and memory T cells.

IL‐15, which is trans‐presented by IL‐15Rα+ cells to neighboring IL‐2Rβ/γC+ cells, is crucial for the development of intestinal intraepithelial lymphocytes (IEL). Parenchymal cells have a major role in the trans‐presentation of IL‐15 to IELs; however, the specific identity of this cell type is unknown. Since trans‐presentation requires cell‐cell contact, we hypothesize that intestinal epithelial cells (IEC) are the parenchymal cell trans‐presenting IL‐15 to IELs. To determine whether IECs trans‐present IL‐15 to developing IELs, we developed a mouse model with IL‐15Rα expressed exclusively by the IECs. This model was generated by driving IL‐15Rα under the Villin promoter and crossing to the IL‐15Rα−/− background. Analysis of these transgenic mice detected high levels of IL‐15Rα by the IECs. Among the IELs, Thy1‐ CD8αα TCRαβ and TCRγδ subsets were restored to normal or higher levels as compared to control and IL‐15Rα−/− mice. The increases in cell number did not appear to be the result of cell expansion as no differences in proliferation rate was detected among transgenic, control, or IL‐15Rα−/− mice. Collectively, this study demonstrates that IL‐15Rα expression by IECs alone is completely sufficient to direct all the IL‐15‐mediated events driving the development of CD8αα IELs. This research is supported by NIH grant AI070910 and the MDACC Trust Fellowship.

Development of pulmonary hypertension is a common and deadly complication of interstitial lung disease. Little is known regarding the cellular and molecular mechanisms that lead to pulmonary hypertension in patients with interstitial lung disease, and effective treatment options are lacking. The purpose of this study was to examine the adenosine 2B receptor (A(2B)R) as a regulator of vascular remodeling and pulmonary hypertension secondary to pulmonary fibrosis. To accomplish this, cellular and molecular changes in vascular remodeling were monitored in mice exposed to bleomycin in conjunction with genetic removal of the A(2B)R or treatment with the A(2B)R antagonist GS-6201. Results demonstrated that GS-6201 treatment or genetic removal of the A(2B)R attenuated vascular remodeling and hypertension in our model. Furthermore, direct A(2B)R activation on vascular cells promoted interleukin-6 and endothelin-1 release. These studies identify a novel mechanism of disease progression to pulmonary hypertension and support the development of A(2B)R antagonists for the treatment of pulmonary hypertension secondary to interstitial lung disease.

Idiopathic pulmonary fibrosis (IPF) is a lethal, fibroproliferative disease. Pulmonary hypertension (PH) can develop secondary to IPF and increase mortality. Alternatively, activated macrophages (AAMs) contribute to the pathogenesis of both IPF and PH. Here we hypothesized that adenosine signaling through the ADORA2B on AAMs impacts the progression of these disorders and that conditional deletion of ADORA2B on myeloid cells would have a beneficial effect in a model of these diseases. Conditional knockout mice lacking ADORA2B on myeloid cells (Adora2B f/f -LysM Cre ) were exposed to the fibrotic agent bleomycin (BLM; 0.035 U/g body weight, i.p.). At 14, 17, 21, 25, or 33 d after exposure, SpO 2 , bronchoalveolar lavage fluid (BALF), and histologic analyses were performed. On day 33, lung function and cardiovascular analyses were determined. Markers for AAM and mediators of fibrosis and PH were assessed. Adora2B f/f -LysM Cre mice presented with attenuated fibrosis, improved lung function, and no evidence of PH compared with control mice exposed to BLM. These findings were accompanied by reduced expression of CD206 and arginase-1, markers for AAMs. A 10-fold reduction in IL-6 and a 5-fold decrease in hyaluronan, both linked to lung fibrosis and PH, were also observed. These data suggest that activation of the ADORA2B on macrophages plays an active role in the pathogenesis of lung fibrosis and PH.-Karmouty-Quintana, H., Philip, K., Acero, L. F., Chen, N.-Y., Weng, T., Molina, J. G., Luo, F., Davies, J., Le, N.-B., Bunge, I., Volcik, K. A., Le, T.-T. T., Johnston, R. A., Xia, Y., Eltzschig, H. K., Blackburn, M. R. Deletion of ADORA2B from myeloid cells dampens lung fibrosis and pulmonary hypertension. FASEB J. 29, 50-60 (2015). www.fasebj.org