SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: T helper cell

172

Graft-versus-host disease is one of the major transplant-related complications in allogeneic hematopoietic stem cell transplantation. Continued efforts have been made to prevent the occurrence of severe graft-versus-host disease by eliminating or suppressing donor-derived effector T cells. Conventional immunosuppression does not adequately prevent graft-versus-host disease, especially in mismatched transplants. Unfortunately, elimination of donor-derived T cells impairs stem cell engraftment, and delays immunologic reconstitution, rendering the recipient susceptible to post-transplant infections and disease relapse, with potentially lethal consequences. In this review, we discuss the role of dynamic immune regulation in controlling graft-versus-host disease, and how cell-based therapies are being developed using regulatory T cells and other tolerogenic cells for the prevention and treatment of graft-versus-host disease. In addition, advances in the design of cytoreductive conditioning regimens to selectively target graft-versus-host disease-inducing donor-derived T cells that have improved the safety of allogeneic stem cell transplantation are reviewed. Finally, we discuss advances in our understanding of the tolerogenic facilitating cell population, a phenotypically and functionally distinct population of bone marrow-derived cells which promote hematopoietic stem cell engraftment while reducing the risk of graft-versus-host disease.

Concepts: Immune system, Immunology, Graft-versus-host disease, T helper cell, T cells, Organ transplant, Hematopoietic stem cell transplantation, Hematopoietic stem cell

167

To isolate and characterize indigenous algicidal bacteria and their algae-lysing compounds active against Microcystis aeruginosa, strains TH1, TH2, and FACHB 905.

Concepts: Immune system, Bacteria, Fungus, T helper cell, Pseudomonas aeruginosa, Bacterial cell structure, Vermilion, Carmine

162

Macrophage polarization is increasingly recognised as an important pathogenetic factor in inflammatory and neoplastic diseases. Proinflammatory M1 macrophages promote T helper (Th) 1 responses and show tumoricidal activity. M2 macrophages contribute to tissue repair and promote Th2 responses. CD68 and CD163 are used to identify macrophages in tissue sections. However, characterisation of polarised macrophages in situ has remained difficult. Macrophage polarisation is regulated by transcription factors, pSTAT1 and RBP-J for M1, and CMAF for M2. We reasoned that double-labelling immunohistochemistry for the detection of macrophage markers together with transcription factors may be suitable to characterise macrophage polarisation in situ. To test this hypothesis, we have studied conditions associated with Th1- and Th2-predominant immune responses: infectious mononucleosis and Crohn’s disease for Th1 and allergic nasal polyps, oxyuriasis, wound healing and foreign body granulomas for predominant Th2 response. In all situations, CD163+ cells usually outnumbered CD68+ cells. Moreover, CD163+ cells, usually considered as M2 macrophages, co-expressing pSTAT1 and RBP-J were found in all conditions examined. The numbers of putative M1 macrophages were higher in Th1- than in Th2-associated diseases, while more M2 macrophages were seen in Th2- than in Th1 related disorders. In most Th1-related diseases, the balance of M1 over M2 cells was shifted towards M1 cells, while the reverse was observed for Th2-related conditions. Hierarchical cluster analysis revealed two distinct clusters: cluster I included Th1 diseases together with cases with high numbers of CD163+pSTAT1+, CD68+pSTAT1+, CD163+RBP-J+ and CD68+RBP-J+ macrophages; cluster II comprised Th2 conditions together with cases displaying high numbers of CD163+CMAF+ and CD68+CMAF+ macrophages. These results suggest that the detection of pSTAT1, RBP-J, and CMAF in the context of CD68 or CD163 expression is a suitable tool for the characterisation of macrophage polarisation in situ. Furthermore, CD163 cannot be considered a reliable M2 marker when used on its own.

Concepts: AIDS, Immune system, White blood cell, Asthma, Macrophage, Apoptosis, Allergy, T helper cell

162

Smoking is a common addiction and a leading cause of disease. Chronic nicotine exposure is known to activate nicotinic acetylcholine receptors (nAChRs) in immune cells. We demonstrate a novel role for α4 nAChRs in the effect of nicotine on T-cell proliferation and immunity. Using cell based sorting and proteomic analysis we define an α4 nAChR expressing helper T-cell population (α4+CD3+CD4+) and show that this group of cells is responsive to sustained nicotine exposure. In circulation, spleen, and thymus we find that nicotine promotes an increase in CD3+CD4+ cells via its activation of the α4 nAChR and regulation of Gαo, Gprin1, and CDC42 signaling within T-cells. In particular, nicotine is found to promote a Th2, adaptive, immunological response within T-cells, which was absent in α4-/- mice. We thus present a new mechanism of α4 nAChR signaling and immune regulation in T-cells, possibly accounting for the effect of smoking on the immune system.

Concepts: Immune system, White blood cell, Immunology, T helper cell, Nicotine, Cell signaling, Acetylcholine, Nicotinic acetylcholine receptor

149

We previously developed novel liposomal nanobubbles (Bubble liposomes; BLs) that oscillate and collapse in an ultrasound field, generating heat and shock waves. We aimed to investigate the feasibility of cancer therapy by the combination of BLs and ultrasound (BLs + ultrasound). In addition, we investigated the anti-tumor mechanism of this cancer therapy. Colon-26 cells were inoculated into the flank of BALB/c mice to induce tumors. After 8 days, BLs or saline was intratumorally injected, followed by transdermal ultrasound exposure of tumor tissue (1 MHz, 0-4 W/cm(2) , 2 min). The anti-tumor effects were evaluated by histology (necrosis) and tumor growth. In vivo cell depletion assays were performed to identify the immune cells responsible for anti-tumor effects. Tumor temperatures were significantly higher when treated with BLs + ultrasound than ultrasound alone. Intratumoral BLs caused extensive tissue necrosis at 3-4 W/cm(2) of ultrasound exposure. In addition, BLs + ultrasound significantly suppressed tumor growth at 2-4 W/cm(2) . In vivo depletion of CD8(+) T cells (not NK or CD4(+) T cells) completely blocked the effect of BLs + ultrasound on tumor growth. These data suggest that CD8(+) T cells play a critical role in tumor growth suppression. Finally, we concluded that BLs + ultrasound which can prime the anti-tumor cellular immune system may be an effective hyperthermia strategy for cancer treatment. This article is protected by copyright. All rights reserved.

Concepts: Immune system, White blood cell, Antibody, Cancer, Apoptosis, Immunology, T helper cell, Humoral immunity

98

Background The unprecedented 2014 epidemic of Ebola virus disease (EVD) has prompted an international response to accelerate the availability of a preventive vaccine. A replication-defective recombinant chimpanzee adenovirus type 3-vectored ebolavirus vaccine (cAd3-EBO), encoding the glycoprotein from Zaire and Sudan species that offers protection in the nonhuman primate model, was rapidly advanced into phase 1 clinical evaluation. Methods We conducted a phase 1, dose-escalation, open-label trial of cAd3-EBO. Twenty healthy adults, in sequentially enrolled groups of 10 each, received vaccination intramuscularly in doses of 2×10(10) particle units or 2×10(11) particle units. Primary and secondary end points related to safety and immunogenicity were assessed throughout the first 4 weeks after vaccination. Results In this small study, no safety concerns were identified; however, transient fever developed within 1 day after vaccination in two participants who had received the 2×10(11) particle-unit dose. Glycoprotein-specific antibodies were induced in all 20 participants; the titers were of greater magnitude in the group that received the 2×10(11) particle-unit dose than in the group that received the 2×10(10) particle-unit dose (geometric mean titer against the Zaire antigen, 2037 vs. 331; P=0.001). Glycoprotein-specific T-cell responses were more frequent among those who received the 2x10(11) particle-unit dose than among those who received the 2×10(10) particle-unit dose, with a CD4 response in 10 of 10 participants versus 3 of 10 participants (P=0.004) and a CD8 response in 7 of 10 participants versus 2 of 10 participants (P=0.07). Conclusions Reactogenicity and immune responses to cAd3-EBO vaccine were dose-dependent. At the 2×10(11) particle-unit dose, glycoprotein Zaire-specific antibody responses were in the range reported to be associated with vaccine-induced protective immunity in challenge studies involving nonhuman primates. Clinical trials assessing cAd3-EBO are ongoing. (Funded by the Intramural Research Program of the National Institutes of Health; VRC 207 ClinicalTrials.gov number, NCT02231866 .).

Concepts: Immune system, Antibody, Vaccination, Immunology, T helper cell, Immunity, Ebola, Western Red Colobus

75

Background Moderate-to-severe asthma remains poorly treated. We evaluated the efficacy and safety of dupilumab (SAR231893/REGN668), a fully human monoclonal antibody to the alpha subunit of the interleukin-4 receptor, in patients with persistent, moderate-to-severe asthma and elevated eosinophil levels. Methods We enrolled patients with persistent, moderate-to-severe asthma and a blood eosinophil count of at least 300 cells per microliter or a sputum eosinophil level of at least 3% who used medium-dose to high-dose inhaled glucocorticoids plus long-acting beta-agonists (LABAs). We administered dupilumab (300 mg) or placebo subcutaneously once weekly. Patients were instructed to discontinue LABAs at week 4 and to taper and discontinue inhaled glucocorticoids during weeks 6 through 9. Patients received the study drug for 12 weeks or until a protocol-defined asthma exacerbation occurred. The primary end point was the occurrence of an asthma exacerbation; secondary end points included a range of measures of asthma control. Effects on various type 2 helper T-cell (Th2)-associated biomarkers and safety and tolerability were also evaluated. Results A total of 52 patients were assigned to the dupilumab group, and 52 patients were assigned to the placebo group. Baseline characteristics were similar in the two groups. Three patients had an asthma exacerbation with dupilumab (6%) versus 23 with placebo (44%), corresponding to an 87% reduction with dupilumab (odds ratio, 0.08; 95% confidence interval, 0.02 to 0.28; P<0.001). Significant improvements were observed for most measures of lung function and asthma control. Dupilumab reduced biomarkers associated with Th2-driven inflammation. Injection-site reactions, nasopharyngitis, nausea, and headache occurred more frequently with dupilumab than with placebo. Conclusions In patients with persistent, moderate-to-severe asthma and elevated eosinophil levels who used inhaled glucocorticoids and LABAs, dupilumab therapy, as compared with placebo, was associated with fewer asthma exacerbations when LABAs and inhaled glucocorticoids were withdrawn, with improved lung function and reduced levels of Th2-associated inflammatory markers. (Funded by Sanofi and Regeneron Pharmaceuticals; ClinicalTrials.gov number, NCT01312961 .).

Concepts: Immune system, Inflammation, White blood cell, Asthma, Lung, Monoclonal antibodies, T helper cell, Regeneron

49

Blood pressure regulation is known to be maintained by a neuro-endocrine circuit, but whether immune cells contribute to blood pressure homeostasis has not been determined. We previously showed that CD4(+) T lymphocytes that express choline acetyltransferase (ChAT), which catalyzes the synthesis of the vasorelaxant acetylcholine, relay neural signals. Here we show that these CD4(+)CD44(hi)CD62L(lo) T helper cells by gene expression are a distinct T-cell population defined by ChAT (CD4 TChAT). Mice lacking ChAT expression in CD4(+) cells have elevated arterial blood pressure, compared to littermate controls. Jurkat T cells overexpressing ChAT (JTChAT) decreased blood pressure when infused into mice. Co-incubation of JTChAT and endothelial cells increased endothelial cell levels of phosphorylated endothelial nitric oxide synthase, and of nitrates and nitrites in conditioned media, indicating increased release of the potent vasorelaxant nitric oxide. The isolation and characterization of CD4 TChAT cells will enable analysis of the role of these cells in hypotension and hypertension, and may suggest novel therapeutic strategies by targeting cell-mediated vasorelaxation.

Concepts: Immune system, White blood cell, Gene, Atherosclerosis, Blood pressure, T helper cell, Nitric oxide, Nitric oxide synthase

34

Four Ebola patients received care at Emory University Hospital, presenting a unique opportunity to examine the cellular immune responses during acute Ebola virus infection. We found striking activation of both B and T cells in all four patients. Plasmablast frequencies were 10-50% of B cells, compared with less than 1% in healthy individuals. Many of these proliferating plasmablasts were IgG-positive, and this finding coincided with the presence of Ebola virus-specific IgG in the serum. Activated CD4 T cells ranged from 5 to 30%, compared with 1-2% in healthy controls. The most pronounced responses were seen in CD8 T cells, with over 50% of the CD8 T cells expressing markers of activation and proliferation. Taken together, these results suggest that all four patients developed robust immune responses during the acute phase of Ebola virus infection, a finding that would not have been predicted based on our current assumptions about the highly immunosuppressive nature of Ebola virus. Also, quite surprisingly, we found sustained immune activation after the virus was cleared from the plasma, observed most strikingly in the persistence of activated CD8 T cells, even 1 mo after the patients' discharge from the hospital. These results suggest continued antigen stimulation after resolution of the disease. From these convalescent time points, we identified CD4 and CD8 T-cell responses to several Ebola virus proteins, most notably the viral nucleoprotein. Knowledge of the viral proteins targeted by T cells during natural infection should be useful in designing vaccines against Ebola virus.

Concepts: Immune system, Virus, T helper cell, T cell, Antigen, Major histocompatibility complex, T cell receptor, Cytotoxic T cell

30

Background. We sought to quantify the survival benefits attributable to antiretroviral therapy (ART) in South Africa since 2004.Methods. We used the Cost-Effectiveness of Preventing AIDS Complications-International model (CEPAC) to simulate 8 cohorts of human immunodeficiency virus (HIV)-infected patients initiating ART each year during 2004-2011. Model inputs included cohort-specific mean CD4(+) T-cell count at ART initiation (112-178 cells/µL), 24-week ART suppressive efficacy (78%), second-line ART availability (2.4% of ART recipients), and cohort-specific 36-month retention rate (55%-71%). CEPAC simulated survival twice for each cohort, once with and once without ART. The sum of the products of per capita survival differences and the total numbers of persons initiating ART for each cohort yielded the total survival benefits.Results. Lifetime per capita survival benefits ranged from 9.3 to 10.2 life-years across the 8 cohorts. Total estimated population lifetime survival benefit for all persons starting ART during 2004-2011 was 21.7 million life-years, of which 2.8 million life-years (12.7%) had been realized by December 2012. By 2030, benefits reached 17.9 million life-years under current policies, 21.7 million life-years with universal second-line ART, 23.3 million life-years with increased linkage to care of eligible untreated patients, and 28.0 million life-years with both linkage to care and universal second-line ART.Conclusions. We found dramatic past and potential future survival benefits attributable to ART, justifying international support of ART rollout in South Africa.

Concepts: Antiretroviral drug, HIV, AIDS, Protease inhibitor, Viral load, Africa, T helper cell, South Africa