Eosinophils from Hematopoietic Stem Cell Recipients Suppress Allogeneic T Cell Proliferation

Hematopoiesis in the spleen after engraftment in unrelated cord blood transplantation evaluated by 18F-FLT PET imaging

Cord blood is an important donor source for allogeneic hematopoietic stem cell transplantation (allo-HSCT), with its unique composition and quality of hematopoietic cells. The proliferation site and potency of infused hematopoietic stem cells in humans may vary between stem cell sources. We investigated this possibility in a prospective, exploratory study to assess hematopoietic dynamics using the radiopharmaceutical 3'-deoxy-3'-18F-fluorothymidine (18F-FLT), a thymidine analog used in positron emission tomography imaging, before allo-HSCT and on days 50 and 180 after allo-HSCT. We evaluated 11 patients with hematological malignancies who underwent allo-HSCT [five with peripheral blood stem cell transplantation (PBSCT) and six with unrelated cord blood transplantation (UCBT)]. Before allo-HSCT, 18F-FLT uptake did not differ between the two groups. At day 50, 18F-FLT uptake in the spleen was significantly greater in the UCBT group than in the PBSCT group (p = 0.0043), with no difference in whole-body bone marrow. At day 180, the differences in spleen uptake had diminished, and there were no differences between groups in whole-body bone marrow or the spleen, except for the sternum. The persistence of splenic hematopoiesis after engraftment in the UCBT group may reflect the complex systemic homing and proliferation mechanisms of cord blood hematopoietic cells.

Investigating immune profile by CyTOF in individuals with long-standing type 1 diabetes

Type 1 diabetes (T1D) is an autoimmune disease caused by T-cell mediated destruction of pancreatic beta cells. Eosinophils are found in pancreatic tissue from individuals with T1D. Eosinophilic suppression of T cells is dependent of the protein galectin-10. Little is known when it comes to the role of eosinophil granulocytes in type 1 diabetes. Here we show that individuals with long-standing T1D had lower levels of galectin-10^hi eosinophils and a subgroup of galectin-10^hi eosinophils were entirely absent in all T1D patients. In addition, 7% immature eosinophils were present in the circulation of T1D patients whereas 0.8% in healthy individuals. Furthermore, higher levels of CD4+CD8+ T cells and Th17 cells were observed in patients with T1D. Blood samples from 12 adult individuals with long-standing T1D and 12 healthy individuals were compared using cytometry by time-of-flight. Lower levels of galectin-10^hi eosinophils, which are potent T cell suppressors, in individuals with T1D could indicate that activated T cells are enabled to unrestrictedly kill the insulin producing beta cells. This is the first study showing absence of galectin-10^hi eosinophilic subgroup in individuals with T1D compared with healthy controls. This study is a first important step toward unraveling the role of the eosinophils in patients with T1D.

Early-Phase Peripheral Blood Eosinophilia Predicts Lower Overall and Non-Relapse Mortality After Single-Unit Cord Blood Transplantation

Peripheral blood eosinophilia has been associated with the development of graft-versus-host disease (GVHD) and survival after allogeneic hematopoietic cell transplantation (HCT). However, the impacts of eosinophilia on cord blood transplantation (CBT) outcomes remain unclear. The objective of this study was to examine the associations between eosinophilia and overall survival, relapse incidence, non-relapse mortality, and acute and chronic GVHD after single-unit CBT for adults. We retrospectively analyzed the data for 225 adult patients who received single-unit CBT at our institute between March 2004 and March 2020. The cumulative incidence of eosinophilia, defined as an absolute eosinophil count of ≥500 × 10⁶/L in peripheral blood, was 48.9% (95% confidence interval, 42.2% to 55.2%) at 60 days after CBT. Recipient cytomegalovirus seronegative status and higher cryopreserved cord blood CD34⁺ cell dose were significantly associated with a higher incidence of eosinophilia after CBT. Among patients who achieved neutrophil recovery, neutrophil recovery was significantly earlier in patient with eosinophilia compared to those without eosinophilia (P = .016). Serum levels of interleukin-5 at 4 weeks were significantly higher in patients with eosinophilia compared with those without eosinophilia (P = .041). Multivariate analysis, in which the development of eosinophilia was treated as a time-dependent covariate, showed that eosinophilia was significantly associated with lower overall mortality (hazard ratio [HR], .58; P = .034) and non-relapse mortality (HR, .41; P = .029), but not relapse incidence or development of acute or chronic GVHD. Our data suggested that early-phase eosinophilia is a predictor of favorable outcomes in adult patients undergoing single-unit CBT.

Kinetic studies of galectin-10 release from eosinophils exposed to proliferating T cells

Galectin-10 is involved in the T cell suppressive activity of regulatory T cells and eosinophils alike. We have identified a subpopulation of T cell suppressive eosinophils that express CD16 on the surface and contain more galectin-10 compared with conventional CD16-negative eosinophils. Our main goal was to determine how the intracellular protein galectin-10 is released from eosinophils when exposed to proliferating T cells and if such release could be inhibited. Confocal microscopy and imaging flow cytometry were used to study the release of galectin-10 from eosinophils incubated with polyclonally activated T cells. T cell proliferation was monitored by measurement of the incorporation of [³ H]-thymidine. Initially, galectin-10-containing synapses formed between eosinophils and T cells. Subsequently, the plasma membrane of eosinophils began to disintegrate and cap-like accumulations of galectin-10 budded on the eosinophil cell surface. Lastly, eosinophil extracellular traps composed of nuclear DNA and galectin-10 were freed. It was solely the CD16-expressing suppressive eosinophils that formed synapses and eosinophil extracellular traps containing galectin-10. Dissolution of the extracellular traps by DNase I partly abrogated the T cell suppression exerted by eosinophils. Extracellular trap formation has mainly been associated with anti-bacterial defense, but we show a new putative function of these cellular formations, as mediators of T cell suppression by enabling the release of galectin-10 from eosinophils.

Activation of group 2 innate lymphoid cells alleviates aging-associated cognitive decline

Increasing evidence has challenged the traditional view about the immune privilege of the brain, but the precise roles of immune cells in regulating brain physiology and function remain poorly understood. Here, we report that tissue-resident group 2 innate lymphoid cells (ILC2) accumulate in the choroid plexus of aged brains. ILC2 in the aged brain are long-lived, are relatively resistant to cellular senescence and exhaustion, and are capable of switching between cell cycle dormancy and proliferation. They are functionally quiescent at homeostasis but can be activated by IL-33 to produce large amounts of type 2 cytokines and other effector molecules in vitro and in vivo. Intracerebroventricular transfer of activated ILC2 revitalized the aged brain and enhanced the cognitive function of aged mice. Administration of IL-5, a major ILC2 product, was sufficient to repress aging-associated neuroinflammation and alleviate aging-associated cognitive decline. Targeting ILC2 in the aged brain may provide new avenues to combat aging-associated neurodegenerative disorders.

Kupffer cell activation by different microbial lysates: Toll-like receptor-2 plays pivotal role on thromboxane A2 production in mice and humans

Thromboxane (TX) A₂ has been identified as an important intrahepatic vasoconstrictor upon Kupffer cell (KC) activation during infections such as spontaneous bacterial peritonitis (SBP). The study aimed to investigate the role of TLRs in the TXA₂ increase in liver nonparenchymal cells and their related mechanisms. Here, we identified TLR-2 as a common pathway for different microbials: microbial lysates including Gram-positive bacteria, Gram-negative bacteria, and fungi all increased TXA₂ secretion via activation of TLR-2 in human KCs, accompanied by increased expression and phosphorylation of Myd88-related pathway. Of all TLR agonists, only TLR-1, -2, and -4 agonists increased TXA₂ in human KCs. These results were further confirmed by mouse liver nonparenchymal cells. Comparing the effects of TLR-1, -2, and -4 antagonists, only TLR-2 antagonist showed inhibitory effects with all tested microbial lysates. Pretreatment with TLR-2 antagonist in human KCs blocked the secretion of IL-10, CXCL-10, TNF-α, and IL-6 induced by Gram-positive and Gram-negative bacterial stimulation. IL-23 and IL-1β were only induced by Gram-negative bacteria. Thus, TLR-2 might be a potential marker and an attractive target for future treatment of patients with SBP. In addition, IL-23 and IL-1β might distinguish early between Gram-positive and Gram-negative SBP.

Expression and significance of molecular profiles on eosinophils of children with food allergy

Peripheral blood eosinophils may increase in food allergy (FA). However, the correlation between activation status of blood eosinophils and features of FA are unknown. We collected 25 cases of FA out-patients with increased number of eosinophils and 20 healthy children. Eosinophil surface markers were analyzed by flow cytometry. We found that CD23, CD44, CD54, and CRTH2 were positive on different eosinophils and that their expressions were increased in FA patients compared to the control individuals. There was a positive correlation with strong protein–protein interactions between the four eosinophil surface markers which were functionally involved in regulation of cell killing, interferon-gamma-mediated signaling pathway, and Epstein–Barr virus infection pathway. Thus, blood eosinophils change their phenotype during FA and induce significant gene regulation changes that may cause FA with eosinophilia. Detection of the expression of CD23, CD44, CD54, and CRTH2 on eosinophils can be used as indicators of FA with eosinophilia.

Differences in eosinophil molecular profiles between children and adults with eosinophilic esophagitis

BACKGROUND

Eosinophilic esophagitis (EoE) afflicts both children and adults. It has been debated whether pediatric EoE and adult EoE represent different disease entities. The objectives of this study were to determine whether the blood eosinophil molecular pattern of children with EoE is (i) distinct from that of healthy children; and (ii) different from that of adults with EoE.

METHODS

Blood eosinophils from children and adults with EoE, and healthy controls, were analyzed with flow cytometry regarding levels of CD23, CD44, CD54, CRTH2, FOXP3, and galectin-10. Eosinophil FOXP3 and galectin-10 mRNA levels were determined by qPCR. The data were analyzed using a multivariate method of pattern recognition.

RESULTS

An eosinophil molecular pattern capable of distinguishing children with EoE from control children was identified. A smaller fraction of eosinophils from children with EoE expressed CD44 and a larger fraction expressed CRTH2 than the controls. Eosinophils from children with EoE also had higher levels of galectin-10 mRNA and lower levels of FOXP3 mRNA. The eosinophils from children with EoE had lower levels of surface CD54 and of FOXP3 mRNA compared with the eosinophils from the adult patients. A key finding was the detection in healthy individuals of age-related differences in the levels of several eosinophil markers.

CONCLUSIONS

Children with EoE can be distinguished from healthy children based on the molecular patterns of their blood eosinophils. Age-related physiologic differences in eosinophil molecular patterns may partly explain the different blood eosinophil phenotypes in children vs adults with EoE.

Regulatory Eosinophils Suppress T Cells Partly through Galectin-10

Eosinophils have the capacity to regulate the function of T cell subsets. Our aim was to test the hypothesis of the existence of a regulatory subset of eosinophils. Human eosinophils were incubated with T cells that were stimulated with allogeneic leukocytes or CD3/CD28 cross-linking. After 2 d of coculture, 11% of the eosinophils gained CD16 expression. A CD16^hi subset of eosinophils, encompassing 1-5% of all eosinophils, was also identified in the blood of healthy subjects. FACS sorting showed that these CD16^hi eosinophils were significantly stronger suppressors of T cell proliferation than were conventional CD16^neg eosinophils. Human eosinophils contain stores of the immunoregulatory protein galectin-10. We found that Ab-mediated neutralization of galectin-10 partially abrogated the suppressive function of the eosinophils. Moreover, recombinant galectin-10 by itself was able to suppress T cell proliferation. Finally, we detected galectin-10-containing immune synapses between eosinophils and lymphocytes. To conclude, we describe a subset of suppressive eosinophils expressing CD16 that may escape detection because CD16-based negative selection is the standard procedure for the isolation of human eosinophils. Moreover, we show that galectin-10 functions as a T cell-suppressive molecule in eosinophils.

Eosinophils from eosinophilic oesophagitis patients have T cell suppressive capacity and express FOXP3

Eosinophilic esophagitis (EoE) is an antigen-driven T cell-mediated chronic inflammatory disease where food and environmental antigens are thought to have a role. Human eosinophils express the immunoregulatory protein galectin-10 and have T cell suppressive capacity similar to regulatory T cells (Tregs ). We hypothesized that one function of eosinophils in EoE might be to regulate the T cell-driven inflammation in the oesophagus. This was tested by evaluating the suppressive capacity of eosinophils isolated from the blood of adult EoE patients in a mixed lymphocyte reaction. In addition, eosinophilic expression of forkhead box protein 3 (FOXP3), the canonical transcription factor of Tregs , was determined by conventional and imaging flow cytometry, quantitative polymerase chain reaction (qPCR), confocal microscopy and immunoblotting. It was found that blood eosinophils from EoE patients had T cell suppressive capacity, and that a fraction of the eosinophils expressed FOXP3. A comparison of EoE eosinophils with healthy control eosinophils indicated that the patients' eosinophils had inferior suppressive capacity. Furthermore, a higher percentage of the EoE eosinophils expressed FOXP3 protein compared with the healthy eosinophils, and they also had higher FOXP3 protein and mRNA levels. FOXP3 was found in the cytosol and nucleus of the eosinophils from both the patients and healthy individuals, contrasting with the strict nuclear localization of FOXP3 in Tregs . To conclude, these findings suggest that the immunoregulatory function of eosinophils may be impaired in EoE.

Emerging Roles for Eosinophils in the Tumor Microenvironment

Eosinophils are evolutionary conserved cells largely studied in the context of allergy. Although eosinophils were first described in tumors more than 120 years ago, their roles in cancer are often overlooked. This is puzzling given their potent immune modulatory, cytotoxic, and/or tissue repair capabilities, and recent studies demonstrating key roles for eosinophils in contexts far beyond their 'classical' field (e.g., metabolism, thermogenesis, and tissue regeneration). Recent data suggest that this frequently ignored cell is emerging as a potent immune effector and immune modulator in the tumor microenvironment. This review discusses the relevance of eosinophils to tumorigenesis and the potential to harness their function in cancer therapies.