Project description:The current model of hematopoiesis only resolves the thymus around the production and establishment of the peripheral T cell pool. However, the role and in situ development of other immune subsets has been overlooked. We aim to demonstrate that during TL1A and IL-18 induced inflammation, the thymus is capable of producing other cell types such as neutrophils, monocytes, and macrophages and that these potentially have other functions aside from supporting T cell development as scavengers. Here we have proven that ex vivo and in vivo treatment with TL1A and IL-18 results in acute thymic atrophy by a massive loss of DP T cells and shrinking of the thymic lobe. By electron microscopy, flow cytometry and single cell we demonstrate that neutrophils are able to maturate inside the thymus lobe in a NOTCH-independent manner. We used fate-mapping tools to elucidate the origin of thymic neutrophils since we observed a great expansion in our culture that is isolated from the influx of BM progenitors. The Rag1-Cre Rosa26-YFP fate mapping model revealed that neutrophils share a common progenitor with T cells, while monocytes/macrophages do not. Furthermore, we found that most of the thymic GMPs (defined as Lin-Sca-1-c-Kit+CD16/32+CD34+) show history of Rag1 expression in comparison with bone marrow GMPs. Additionally, by using Ms4a3-Cre Rosa26Tdtomato fate mapping model we observed that there was not difference in Tdt labeling between the thymus and bone marrow, suggesting that thymic neutrophils still undergo conventional neutrophils pathway arising from GMPs. Moreover, we show that thymic-derived neutrophils are functional and are capable of forming extracellular neutrophils traps (NETs) similarly to benchmark peritoneal neutrophils. We found that the expansion of thymic neutrophils is GM-CSF dependent by using Csf2rb KO mice. Additionally, we identified DR3+ and IL-18Rα+ expressing subsets of ILCs and gdT cells as the cellular source GM-CSF. Lastly, in vivo treatment with TL1A+IL-18 lead to emergency granulopoiesis and an increase of neutrophils in all the organs investigated, including the thymus.
Project description:Emergency granulopoiesis refers to the increased production of neutrophils in bone marrow and their release into circulation induced by severe infection. Several studies point to a critical role for granulocyte colony-stimulating factor (G-CSF) as the main mediator of emergency granulopoiesis. However, the consequences of G-CSF stimulation on the transcriptome of neutrophils and their precursors have not yet been investigated in humans. Here, we examine the changes in mRNA expression induced by administration of G-CSF in vivo, as a model of emergency granulopoiesis in humans. Blood samples were collected from healthy individuals after five days of G-CSF administration. Neutrophil precursors were sorted into discrete stages of maturation by flow cytometry, and RNA was subjected to microarray analysis. mRNA levels were compared to previously published expression levels in corresponding populations of neutrophil precursors isolated from bone marrow of untreated, healthy individuals. 1110 mRNAs were differentially expressed more than 2-fold throughout terminal granulopoiesis. Major changes were seen in pathways involved in apoptosis, cytokine signaling, and Toll-like receptor pathways. In addition, G-CSF treatment reduced the levels of four out of five measured granule proteins in mature neutrophils including the proantibacterial protein hCAP-18, which was completely deficient in neutrophils from G-CSF-treated donors. These results indicate that multiple biological processes are altered in order to satisfy the increased demand for neutrophils during G-CSF-induced emergency granulopoiesis in humans.
Project description:Functional analysis demonstrates that neutrophils generated by emergency granulopoiesis have elevated bactericidal activity when compared to control (steady state) neutrophils. To determine if transcriptomic changes support these functional adaptations, we performed gene expression analysis on emergency granulopoiesis and steady state neutrophils before and after infection.
Project description:GM-CSF controls the development of granulocytes but little is known about the contribution of the downstream mediating transcription factor STAT5A/B. To elucidate this pathway, we generated mice lacking the Stat5a and 5b genes in blood cells. Peripheral neutrophils were decreased and administration of 5-FU and GM-CSF failed to induce granulopoiesis in Stat5a/b-mutant mice. GMPs were isolated and cultured with GM-CSF. Both the number and size of STAT5A/B-null colonies were reduced and GM-CSF-induced survival of mature STAT5A/B-null neutrophils was impaired. Time-lapse cinematography and single cell tracking of GMPs revealed that STAT5A/B-null cells were characterized by a longer generation time and an increased cell death. Gene expression profiling experiments suggested that STAT5A/B directs GM-CSF signaling through the regulation of cell survival genes.
Project description:Fanconi Anemia (FA) is an inherited disorder of DNA-repair caused by mutation in one of 20+ interrelated genes that repair intra-strand DNA crosslinks and rescue collapsed or stalled replication forks. The most common hematologic abnormality in FA is anemia, but progression to bone marrow failure (BMF), clonal hematopoiesis, or acute myeloid leukemia (AML) may also occur. In prior studies, we found that Fanconi DNA-repair is required for successful emergency granulopoiesis; the process for rapid neutrophil production during the innate immune response. Specifically, Fancc-/- mice did not develop neutrophilia in response to emergency granulopoiesis stimuli, but instead exhibited apoptosis of bone marrow hematopoietic stem cells (HSCs) and differentiating neutrophils. Repeated emergency granulopoiesis challenges induced BMF in most Fancc-/- mice, with AML in survivors. In contrast, we found equivalent emergency granulopoiesis-induced neutrophilia in Fancc-/-Tp53+/- mice and wild type (WT) mice, without BMF in either. Since bone marrow neutrophil accumulation triggers termination of emergency granulopoiesis, we hypothesize neutrophilia protects Fancc-/-Tp53+/- bone marrow from the stress of sustained inflammatory physiology, as experienced by Fancc-/- mice.
Project description:GM-CSF controls the development of granulocytes but little is known about the contribution of the downstream mediating transcription factor STAT5A/B. To elucidate this pathway, we generated mice lacking the Stat5a and 5b genes in blood cells. Peripheral neutrophils were decreased and administration of 5-FU and GM-CSF failed to induce granulopoiesis in Stat5a/b-mutant mice. GMPs were isolated and cultured with GM-CSF. Both the number and size of STAT5A/B-null colonies were reduced and GM-CSF-induced survival of mature STAT5A/B-null neutrophils was impaired. Time-lapse cinematography and single cell tracking of GMPs revealed that STAT5A/B-null cells were characterized by a longer generation time and an increased cell death. Gene expression profiling experiments suggested that STAT5A/B directs GM-CSF signaling through the regulation of cell survival genes. Experiment Overall Design: Mice lacking or with the Stat5a and 5b genes in blood cells, which were treated w/o GMP
Project description:Acute systemic inflammation critically alters the function of the immune system, often promoting myelopoiesis at the expense of lymphopoiesis. In the thymus, systemic inflammation results in acute thymic atrophy and, consequently, impaired T-lymphopoiesis. The mechanism by which systemic inflammation impacts the thymus beyond suppressing T-cell development is still unclear. Here, we describe how the synergism between TL1A and IL-18 suppresses T-lymphopoiesis to promote thymic myelopoiesis. The protein levels of these two cytokines were elevated in the thymus during viral-induced thymus atrophy infection with murine cytomegalovirus (MCMV) or pneumonia virus of mice (PVM). In vivo administration of TL1A and IL-18 induced acute thymic atrophy, while thymic neutrophils expanded. Fate mapping with Ms4a3-Cre mice demonstrated that thymic neutrophils emerge from thymic granulocyte-monocyte progenitors (GMPs), while Rag1-Cre fate mapping revealed a common developmental path with lymphocytes. These effects could be modeled ex vivo using neonatal thymic organ cultures (NTOCs), where TL1A and IL-18 synergistically enhanced neutrophil production and egress. NOTCH blockade by the LY411575 inhibitor increased the number of neutrophils in the culture, indicating that NOTCH restricted steady-state thymic granulopoiesis. To promote myelopoiesis, TL1A, and IL-18 synergistically increased GM-CSF levels in the NTOC, which was mainly produced by thymic ILC1s. In support, TL1A- and IL-18-induced granulopoiesis was completely prevented in NTOCs derived from Csf2rb-/- mice and by GM-CSFR antibody blockade, revealing that GM-CSF is the essential factor driving thymic granulopoiesis. Taken together, our findings reveal that TL1A and IL-18 synergism induce acute thymus atrophy while promoting extramedullary thymic granulopoiesis in a NOTCH and GM-CSF-controlled manner.
Project description:Sepsis, the dysregulated host response to infection leading to organ dysfunction, arises from diverse mechanisms that are poorly resolved by sepsis as a syndromic classification, confounding immunotherapy trials. Here we delineate neutrophil and granulopoietic disturbances underlying sepsis pathophysiology. We present a whole blood single-cell multiomic sepsis response atlas (272,993 cells, n=39 individuals), revealing multiple immature neutrophil populations that were collectively immunosuppressive, inhibiting CD4+ T cell proliferation and activation in co-culture. We traced this to altered granulopoiesis using single-cell multiomic mapping of circulating hematopoietic stem cells (HSCs) (29,366 cells, n=27). We show how these features are enriched in a subset of patients, resolving a specific poor outcome endotype (sepsis response signature SRS1). SRS1 patients have increased IL1R2+ immature neutrophils, epigenetic signatures of emergency granulopoiesis transcription factors in HSCs, and STAT3 features across infectious disease settings. Our findings delineate an immunohematopoietic axis, therapeutic targets and stratified medicine approach to sepsis.