When neutrophils meet T cells: Beginnings of a tumultuous relationship with underappreciated potential

Impact of granulocyte contamination on PBMC integrity of shipped blood samples: Implications for multi-center studies monitoring regulatory T cells

In centralized immune monitoring for a multi-center allergen immunotherapy trial, we observed frequent loss of CD4+ T cell integrity following staining of cultured PBMCs with our regulatory T cell flow cytometry panel. Samples were marked by a loss of total cellular events, altered scatter properties, and reduced CD3+CD4+ events. This occurred only in samples that were stained with Foxp3 and were therefore treated with Foxp3 fixation-permeabilization buffer. We identified granulocyte contamination in samples associated with a loss of integrity, and went on to test the impact of granulocyte depletion on day-old blood samples. Granulocyte depletion prevented loss of cell integrity and CD3+CD4+ events, and reduced variability in detection of Foxp3+ cells. Addition of purified neutrophils back to PBMCs altered scatter properties and detection of CD4+ T cells. Implementation of a granulocyte depletion step in our standard operating protocols has reduced assay failure due to loss of sample integrity from 31% to 0%. Routine incorporation of a granulocyte depletion step during PBMC isolation is recommended prior to downstream immune monitoring in blood with next-day processing.

Syphilis Infection Differentially Regulates the Phenotype and Function of γδ T Cells in HIV-1-Infected Patients Depends on the HIV-1 Disease Stage

A rapidly escalating outbreak of syphilis infection has been affected men who have sex with men, particularly those with HIV-1 infection. γδ T cells are unconventional immune cells with two main subsets, Vδ1 T cells and Vδ2 T cells, which possess a combination of innate and adaptive immune features allowing them against HIV-1. However, whether syphilis infection affects the phenotype and function of γδ T cells in HIV-1-infected patients remains unclear, especially in acute HIV-1 infection (AHI). In this study, we enrolled 57 HIV-1-infected patients (24 with HIV-1 infection only and 33 coinfected with syphilis) from an acute HIV-1-infected cohort in Beijing (PRIMO). A comprehensive analysis of γδ T-cell phenotype and function was performed by flow cytometry. We found syphilis coinfection could reverse the imbalance of Vδ1/Vδ2 ratio in AHI. Syphilis infection results in decreased γδ T-cell activation in AHI, but increased γδ T-cell activation in chronic HIV-1 infection (CHI). Moreover, patients with CHI had larger numbers of IL-17-producing γδ T cells than those with AHI, regardless of syphilis status. Thus, syphilis affected the γδ T-cell immune response differently in patients depending on the stages of HIV-1 disease. In addition, the percentage of IL-17-producing γδ T cells was positively correlated with the percentage of neutrophils. These results suggest that the γδ T-cell/IL-17/neutrophil axis is involved in HIV-1 pathogenesis and disease progression. Taken together, our observations provide new insight into the roles of γδ T cells in immunopathogenesis of syphilis and HIV-1 coinfection, particularly during AHI, and our findings may be helpful for the prevention of syphilis and other sexually transmitted infections and highlight the great significance on the remedy of patients coinfected with HIV-1.

The Ambiguous Role of γδ T Lymphocytes in Antitumor Immunity

γδ T cells play a role in immune surveillance because they recognize stress-induced surface molecules and metabolic intermediates that are frequently dysregulated in transformed cells. Hence, γδ T cells have attracted much interest as effector cells in cell-based immunotherapy. Recently, however, it has been realized that γδ T cells can also promote tumorigenesis through various mechanisms including regulatory activity and IL-17 production. In this review we outline both the pathways involved in cancer cell recognition and killing by γδ T cells as well as current evidence for their protumorigenic activity in various models. Finally, we discuss strategies to improve the tumor reactivity of γδ T cells and to counteract their protumorigenic activities, which should open improved perspectives for their clinical application.

Essential role for histone deacetylase 11 (HDAC11) in neutrophil biology

Epigenetic changes in chromatin structure have been recently associated with the deregulated expression of critical genes in normal and malignant processes. HDAC11, the newest member of the HDAC family of enzymes, functions as a negative regulator of IL-10 expression in APCs, as previously described by our lab. However, at the present time, its role in other hematopoietic cells, specifically in neutrophils, has not been fully explored. In this report, for the first time, we present a novel physiologic role for HDAC11 as a multifaceted regulator of neutrophils. Thus far, we have been able to demonstrate a lineage-restricted overexpression of HDAC11 in neutrophils and committed neutrophil precursors (promyelocytes). Additionally, we show that HDAC11 appears to associate with the transcription machinery, possibly regulating the expression of inflammatory and migratory genes in neutrophils. Given the prevalence of neutrophils in the peripheral circulation and their central role in the first line of defense, our results highlight a unique and novel role for HDAC11. With the consideration of the emergence of new, selective HDAC11 inhibitors, we believe that our findings will have significant implications in a wide range of diseases spanning malignancies, autoimmunity, and inflammation.

Neutrophils in Tuberculosis: Heterogeneity Shapes the Way?

Infection with M. tuberculosis remains one of the most common infections in the world. The outcome of the infection depends on host ability to mount effective protection and balance inflammatory responses. Neutrophils are innate immune cells implicated in both processes. Accordingly, during M. tuberculosis infection, they play a dual role. Particularly, they contribute to the generation of effector T cells, participate in the formation of granuloma, and are directly involved in tissue necrosis, destruction, and infection dissemination. Neutrophils have a high bactericidal potential. However, data on their ability to eliminate M. tuberculosis are controversial, and the results of neutrophil depletion experiments are not uniform. Thus, the overall roles of neutrophils during M. tuberculosis infection and factors that determine these roles are not fully understood. This review analyzes data on neutrophil defensive and pathological functions during tuberculosis and considers hypotheses explaining the dualism of neutrophils during M. tuberculosis infection and tuberculosis disease.

Microvesicles released by apoptotic human neutrophils suppress proliferation and IL-2/IL-2 receptor expression of resting T helper cells

Membrane-coated microvesicles (MVs) have been identified as important mediators in intercellular communication. During the process of apoptosis, dying cells dynamically release MVs. Neutrophils are the most abundant type of leukocytes in the circulation. Due to their very short lifespan, it is likely that they are the source of large amounts of apoptotic cell-derived MVs. Here, we show that MVs released by apoptotic human polymorphonuclear neutrophils (apoPMN-MVs), but not the apoptotic neutrophils themselves, selectively suppress the proliferation of CD25 (IL-2Rα)^neg CD127 (IL-7Rα)^pos Th cells in a dose-dependent manner. In contrast, the proliferation of total T cells is not affected by MVs. Importantly, apoPMN-MVs suppress the secretion of IL-2 as well as the expression of and signaling via the IL-2 receptor (IL-2R) by CD25^neg CD127^pos Th cells. Addition of IL-7 strongly reduced the suppression of T-cell proliferation by MVs and the addition of IL-2 completely abrogated the suppressive effect. Thus, apoPMN-MVs suppressed a subset of Th cells by downregulating IL-2 and IL-2R expression and signaling. This may represent an important mechanism to prevent the activation and expansion of resting T cells in the absence of sufficient cytokine stimulation, and thereby maintaining immune tolerance.

Chronic Inflammation and γδ T Cells

The epithelial tissues of the skin, lungs, reproductive tract, and intestines are the largest physical barriers the body has to protect against infection. Epithelial tissues are woven with a matrix of immune cells programed to mobilize the host innate and adaptive immune responses. Included among these immune cells are gamma delta T lymphocytes (γδ T cells) that are unique in their T cell receptor usage, location, and functions in the body. Stress reception by γδ T cells as a result of traumatic epithelial injury, malignancy, and/or infection induces γδ T cell activation. Once activated, γδ T cells function to repair tissue, induce inflammation, recruit leukocytes, and lyse cells. Many of these functions are mediated via the production of cytokines and growth factors upon γδ T cell activation. Pathogenesis of many chronic inflammatory diseases involves γδ T cells; some of which are exacerbated by their presence, while others are improved. γδ T cells require a delicate balance between their need for acute inflammatory mediators to function normally and the detrimental impact imparted by chronic inflammation. This review will focus on the recent progress made in understanding how epithelial γδ T cells influence the pathogenesis of chronic inflammatory diseases and how a balance between acute and chronic inflammation impacts γδ T cell function. Future studies will be important to understand how this balance is achieved.

Restrained Th17 response and myeloid cell infiltration into the central nervous system by human decidua-derived mesenchymal stem cells during experimental autoimmune encephalomyelitis

BACKGROUND

Multiple sclerosis is a widespread inflammatory demyelinating disease. Several immunomodulatory therapies are available, including interferon-β, glatiramer acetate, natalizumab, fingolimod, and mitoxantrone. Although useful to delay disease progression, they do not provide a definitive cure and are associated with some undesirable side-effects. Accordingly, the search for new therapeutic methods constitutes an active investigation field. The use of mesenchymal stem cells (MSCs) to modify the disease course is currently the subject of intense interest. Decidua-derived MSCs (DMSCs) are a cell population obtained from human placental extraembryonic membranes able to differentiate into the three germ layers. This study explores the therapeutic potential of DMSCs.

METHODS

We used the experimental autoimmune encephalomyelitis (EAE) animal model to evaluate the effect of DMSCs on clinical signs of the disease and on the presence of inflammatory infiltrates in the central nervous system. We also compared the inflammatory profile of spleen T cells from DMSC-treated mice with that of EAE control animals, and the influence of DMSCs on the in vitro definition of the Th17 phenotype. Furthermore, we analyzed the effects on the presence of some critical cell types in central nervous system infiltrates.

RESULTS

Preventive intraperitoneal injection of DMSCs resulted in a significant delay of external signs of EAE. In addition, treatment of animals already presenting with moderate symptoms resulted in mild EAE with reduced disease scores. Besides decreased inflammatory infiltration, diminished percentages of CD4(+)IL17(+), CD11b(+)Ly6G(+) and CD11b(+)Ly6C(+) cells were found in infiltrates of treated animals. Early immune response was mitigated, with spleen cells of DMSC-treated mice displaying low proliferative response to antigen, decreased production of interleukin (IL)-17, and increased production of the anti-inflammatory cytokines IL-4 and IL-10. Moreover, lower RORγT and higher GATA-3 expression levels were detected in DMSC-treated mice. DMSCs also showed a detrimental influence on the in vitro definition of the Th17 phenotype.

CONCLUSIONS

DMSCs modulated the clinical course of EAE, modified the frequency and cell composition of the central nervous system infiltrates during the disease, and mediated an impairment of Th17 phenotype establishment in favor of the Th2 subtype. These results suggest that DMSCs might provide a new cell-based therapy for the control of multiple sclerosis.

How Neutrophils Shape Adaptive Immune Responses

Neutrophils are classically considered as cells pivotal for the first line of defense against invading pathogens. In recent years, evidence has accumulated that they are also important in the orchestration of adaptive immunity. Neutrophils rapidly migrate in high numbers to sites of inflammation (e.g., infection, tissue damage, and cancer) and are subsequently able to migrate to draining lymph nodes (LNs). Both at the site of inflammation as well as in the LNs, neutrophils can engage with lymphocytes and antigen-presenting cells. This crosstalk occurs either directly via cell–cell contact or via mediators, such as proteases, cytokines, and radical oxygen species. In this review, we will discuss the current knowledge regarding locations and mechanisms of interaction between neutrophils and lymphocytes in the context of homeostasis and various pathological conditions. In addition, we will highlight the complexity of the microenvironment that is involved in the generation of suppressive or stimulatory neutrophil phenotypes.

Permissive and protective roles for neutrophils in leishmaniasis

Leishmania parasites are the causative agents of leishmaniasis, a neglected tropical disease that causes substantial morbidity and considerable mortality in many developing areas of the world. Recent estimates suggest that roughly 10 million people suffer from cutaneous leishmaniasis (CL), and approximately 76,000 are afflicted with visceral leishmaniasis (VL), which is universally fatal without treatment. Efforts to develop therapeutics and vaccines have been greatly hampered by an incomplete understanding of the parasite's biology and a lack of clear protective correlates that must be met in order to achieve immunity. Although parasites grow and divide preferentially in macrophages, a number of other cell types interact with and internalize Leishmania parasites, including monocytes, dendritic cells and neutrophils. Neutrophils appear to be especially important shortly after parasites are introduced into the skin, and may serve a dual protective and permissive role during the establishment of infection. Curiously, neutrophil recruitment to the site of infection appears to continue into the chronic phase of disease, which may persist for many years. The immunological impact of these cells during chronic leishmaniasis is unclear at this time. In this review we discuss the ways in which neutrophils have been observed to prevent and promote the establishment of infection, examine the role of anti-neutrophil antibodies in mouse models of leishmaniasis and consider recent findings that neutrophils may play a previously unrecognized role in influencing chronic parasite persistence.

Systemic immunity shapes the oral microbiome and susceptibility to bisphosphonate-associated osteonecrosis of the jaw

Background

Osteonecrosis of the jaw (ONJ) is a rare but serious adverse drug effect linked to long-term and/or high-dose exposure to nitrogen-bisphosphonates (N-BP), the standard of care for the treatment of bone fragility disorders. The mechanism leading to bisphosphonate-associated ONJ (BAONJ) is unclear and optimal treatment strategies are lacking. Recent evidence suggests that BAONJ may be linked to drug-induced immune dysfunction, possibly associated with increased susceptibility to infections in the oral cavity. The objective of this investigation was to comprehensively assess the relationship linking immune function, N-BP exposure, the oral microbiome and ONJ susceptibility.

Methods

Leukocyte gene expression of factors important for immunity, wound healing and barrier function were assessed by real-time quantitative PCR and the oral microbiome was characterized by 454 pyrosequencing of the 16S rRNA gene in 93 subjects stratified by N-BP exposure and a history of ONJ.

Results

There were marked differences in the systemic expression of genes regulating immune and barrier functions including RANK (p = 0.007), aryl hydrocarbon receptor (AHR, p < 0.001), and FGF9 (p < 0.001), which were collectively up-regulated in individuals exposed to N-BP without ONJ relative to treatment controls. In contrast, the expression levels of these same genes were significantly down-regulated in those who had experienced BAONJ. Surprisingly, the oral microbiome composition was not directly linked to either BAONJ or N-BP exposure, rather the systemic leukocyte expression levels of RANK, TNFA and AHR each explained 9% (p = 0.04), 12% (p = 0.01), and 7% (p = 0.03) of the oral bacterial beta diversity.

Conclusions

The oral microbiome is unlikely causative of ONJ, rather individuals with BAONJ lacked immune resiliency which impaired their capacity to respond adequately to the immunological stress of N-BP treatment. This may be the common factor linking N-BP and anti-RANK agents to ONJ in at-risk individuals. Preventive and/or therapeutic strategies should target the wound healing deficits present in those with ONJ.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0568-z) contains supplementary material, which is available to authorized users.

Human Vγ9/Vδ2 T cells: Innate adaptors of the immune system

Unconventional T cells are gaining center stage as important effector and regulatory cells that orchestrate innate and adaptive immune responses. Human Vγ9/Vδ2 T cells are amongst the best understood unconventional T cells, as they are easily accessible in peripheral blood, can readily be expanded and manipulated in vitro, respond to microbial infections in vivo and can be exploited for novel tumor immunotherapies. We here review findings that suggest that Vγ9/Vδ2 T cells, and possibly other unconventional human T cells, play an important role in bridging innate and adaptive immunity by promoting the activation and differentiation of various types of antigen-presenting cells (APCs) and even turning into APCs themselves, and thereby pave the way for antigen-specific effector responses and long-term immunological memory. Although the direct physiological relevance for most of these mechanisms still needs to be demonstrated in vivo, these findings may have implications for novel therapies, diagnostic tests and vaccines.

Inhibition of human γδ T cell proliferation and effector functions by neutrophil serine proteases

Human peripheral blood γδ T cells expressing the Vγ9Vδ2 T cell receptor are activated by microbial or endogenous pyrophosphate antigens and indirectly by nitrogen-containing bisphosphonates. Apart from proliferation, such phosphoantigens induce proinflammatory cytokine production including TNF-α and IFN-γ and trigger cytotoxic effector function. Neutrophil granulocytes are known to modulate T cell activation. The neutrophil serine proteases proteinase 3, elastase and cathepsin G have multiple potential targets and promote microbial killing. In this study, we investigated the effect of the three serine proteases on the in vitro proliferation and effector functions of γδ T cells cultured in serum-free medium. All three proteases inhibited the proliferative activity, suppressed the cytokine production and decreased the cytotoxicity of γδ T cells. Further studies indicated that proteolytic cleavage of IL-2 and modulation of butyrophilin 3A1 (CD277) expression might contribute to the overall inhibition.

Neutrophil homeostasis and inflammation: novel paradigms from studying periodontitis

Once viewed as simply antibacterial effector cells packed with antimicrobials, neutrophils are now increasingly appreciated for their regulatory roles in immunity and inflammation. The homeostatic regulation of neutrophils is thus crucial for optimal operation of the immune system. An attractive model to understand mechanistically the role of neutrophils is periodontitis, an oral inflammatory disease that is particularly sensitive to neutrophil alterations in numbers or function. The recruitment and proper activation of neutrophils are largely dependent on leukocyte integrins and complement. This review discusses how these processes are affected by host genetic or microbial factors leading to the development of periodontitis. For instance, both hypo- and hyper-recruitment of neutrophils as a result of deficiencies in the expression of β2 integrins or their negative regulators, respectively, causes unwarranted IL-17-dependent inflammatory bone loss. Moreover, microbial hijacking of C5aR (CD88) signaling in neutrophils impairs their antimicrobial function while promoting destructive inflammatory responses. These studies not only support the concept that neutrophil homeostasis is key to periodontal health but also reveal promising, new therapeutic targets as discussed in the review.

The role of calcium and guanosine 3':5'-monophosphate in the action of acetylcholine on thyroid metabolism

The role of calcium and guanosine 3':5'-monophosphate (cyclic GMP) in the regulation of thyroid metabolism has been investigated in dog thyroid slices. Carbamoylcholine enhanced glucose carbon-1 oxidation, protein iodination, cyclic GMP accumulation and decreased thyrotropin-induced adenosine 3':5'-monophosphate (cyclic AMP) accumulation and iodine secretion; it did not affect protein synthesis. The effects of carbamoylcholine were reproduced under various experimental conditions by supplementary calcium in the medium, ouabain, and in media in which Na+ had been replaced by choline chloride. They were inhibited by lanthanum. These results further support the hypothesis that free intracellular Ca2+ is the intracellular signal for carbamoylcholine effects and suggest that a Na+ -gradient-driven Ca2+ extrusion mechanism operates in the thyroid cell. Mn2+ reproduced the effect of Ca2+ on glucose oxidation, protein iodination and cyclic GMP accumulation in Ca2+ -depleted slices and medium, and thus mimicked some intracellular effects of Ca2+. On the other hand Mn2+ inhibited the carbamoylcholine effect on thyrotropin-induced thyroid secretion and cyclic AMP accumulation, and Ca2+ inhibited the Mn2+-induced cyclic GMP accumulation. This suggests that the two ions compete for the same channel. Similarly Mn2+ inhibited calcium effects in the presence of ionophore A23187. Procaine inhibited protein iodination under all conditions suggesting a primary effect; it also inhibited all carbamoylcholine and ouabain actions. However the drug did not inhibit the effects of choline chloride and its action was reversed by raising carbamoylcholine but not Ca2+ concentration; it is therefore doubtful that procaine acts by blocking Ca2+ channels. In media without added Ca2+, Mn2+ increased cyclic GMP accumulation but did not decrease thyrotropin-induced cyclic AMP accumulation or iodine secretion, which suggests that cyclic GMP cannot be the sole mediator of the latter two effects of carbamoylcholine.