Adoptive transfer of IL-4Rα+ macrophages is sufficient to enhance eosinophilic inflammation in a mouse model of allergic lung inflammation.

BACKGROUND: The IL-4 receptor α (IL-4Rα) chain has a broad expression pattern and participates in IL-4 and IL-13 signaling, allowing it to influence several pathological components of allergic lung inflammation. We previously reported that IL-4Rα expression on both bone marrow-derived and non-bone marrow-derived cells contributed to the severity of allergic lung inflammation. There was a correlation between the number of macrophages expressing the IL-4Rα, CD11b, and IA(d), and the degree of eosinophilia in ovalbumin challenged mice. The engagement of the IL-4Rα by IL-4 or IL-13 is able to stimulate the alternative activation of macrophages (AAM). The presence of AAM has been correlated with inflammatory responses to parasites and allergens. Therefore, we hypothesized that IL-4Rα⁺ AAM play an active role in allergic lung inflammation. To directly determine the role of AAM in allergic lung inflammation, M-CSF-dependent macrophages (BMM) were prepared from the bone-marrow of IL-4Rα positive and negative mice and transferred to IL-4RαxRAG2(-/-) mice. Wild type TH2 cells were provided exogenously. RESULTS: Mice receiving IL-4Rα(+/+) BMM showed a marked increase in the recruitment of eosinophils to the lung after challenge with ovalbumin as compared to mice receiving IL-4Rα(-/-) BMM. As expected, the eosinophilic inflammation was dependent on the presence of TH2 cells. Furthermore, we observed an increase in cells expressing F4/80 and Mac3, and the AAM marker YM1/2 in the lungs of mice receiving IL-4Rα(+/+) BMM. The BAL fluid from these mice contained elevated levels of eotaxin-1, RANTES, and CCL2. CONCLUSIONS: These results demonstrate that transfer of IL-4Rα + macrophages is sufficient to enhance TH2-driven, allergic inflammation. They further show that stimulation of macrophages through IL-4Rα leads to their alternative activation and positive contribution to the TH2-driven allergic inflammatory response in the lung. Since an increase in AAM and their products has been observed in patients with asthma exacerbations, these results suggest that AAM may be targeted to alleviate exacerbations.

An atopy-associated polymorphism in the ectodomain of the IL-4R(alpha) chain (V50) regulates the persistence of STAT6 phosphorylation.

Several commonly occurring polymorphisms in the IL-4R(alpha) have been associated with atopy in humans; the Q576R and the S503P polymorphisms reside in the cytoplasmic domain, whereas the I50 to V50 polymorphism resides in the extracellular domain of the IL-4R(alpha). The effects of these polymorphisms on signaling remain controversial. To determine the effect of the polymorphisms on IL-4 signaling in human cells, we stably transfected the human monocytic cell line U937 with murine IL-4R(alpha) cDNA bearing the I or V at position 50 and the P503/R576 double mutant. Each form of the murine IL-4R(alpha) mediated tyrosine phosphorylation of STAT6 in response to murine IL-4 treatment similar to the induction of tyrosine phosphorylation by human IL-4 signaling through the endogenous human IL-4R(alpha). After IL-4 removal, tyrosine-phosphorylated STAT6 rapidly decayed in cells expressing I50 or P503R576 murine IL-4Ralpha. In contrast, STAT6 remained significantly phosphorylated for several hours after murine IL-4 withdrawal in cells expressing the V50 polymorphism. This persistence in tyrosine-phosphorylated STAT6 was associated with persistence in CIS mRNA expression. Blocking IL-4 signaling during the decay phase using the JAK inhibitor AG490 or the anti-IL-4R(alpha) Ab M1 abrogated the persistence of phosphorylated STAT6 observed in the V50-IL-4R(alpha)-expressing cells. These results indicate that the V50 polymorphism promotes sustained STAT6 phosphorylation and that this process is mediated by continued engagement of IL-4R(alpha), suggesting enhanced responses of V50 IL-4R when IL-4 is limiting.

Meeting report: Global vaccine and immunization research forum.

Building on the success of the first Global Vaccine and Immunization Research Forum (GVIRF), the World Health Organization, the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health in the United States of America, and the Bill & Melinda Gates Foundation convened the second GVIRF in March 2016. Leading scientists, vaccine developers, and public health officials from around the world discussed scientific advances and innovative technologies to design and deliver vaccines as well as novel tools and approaches to increase the uptake of vaccines throughout the world. This report summarizes the discussions and conclusions from the forum participants.

Global Vaccine and Immunization Research Forum: Opportunities and challenges in vaccine discovery, development, and delivery.

The World Health Organization, the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health, and the Bill & Melinda Gates Foundation convened the first Global Vaccine and Immunization Research Forum (GVIRF) in March 2014. This first GVIRF aimed to track recent progress of the Global Vaccine Action Plan research and development agenda, identify opportunities and challenges, promote partnerships in vaccine research, and facilitate the inclusion of all stakeholders in vaccine research and development. Leading scientists, vaccine developers, and public health officials from around the world discussed scientific and technical challenges in vaccine development, research to improve the impact of immunization, and regulatory issues. This report summarizes the discussions and conclusions from the forum participants.

Complex role of the IL-4 receptor alpha in a murine model of airway inflammation: expression of the IL-4 receptor alpha on nonlymphoid cells of bone marrow origin contributes to severity of inflammation.

Recent studies have suggested the IL-4Ralpha expressed on lung epithelium is necessary for TH2-mediated goblet cell differentiation and mucus hypersecretion in a murine model of allergic lung disease. However, the IL-4Ralpha is expressed on numerous cell types that could contribute to the overall pathology and severity of asthma. The relative role of the receptor on these cells has not yet been conclusively delineated. To dissect the contribution of IL-4Ralpha in the development of pulmonary allergic responses, we generated murine radiation bone marrow (BM) chimeras. BM from IL-4Ralpha(+) or IL-4Ralpha(-) mice was transferred into recipient mice that expressed or lacked IL-4Ralpha. In the absence of IL-4Ralpha in recipient mice, there was no goblet cell metaplasia or mucus hypersecretion in response to OVA, even in the presence of TH2 cells and substantial eosinophilic infiltration. More importantly, we found that expression of the IL-4Ralpha on a nonlymphoid, MHC class II(+), BM-derived cell type contributes to the severity of inflammation and mucus production. These results suggest that IL-4 and IL-13 contribute to the development of allergic inflammation by stimulating a complex interaction between IL-4Ralpha(+) cell types of both bone marrow and non-bone marrow origin.