Humoral Arm Research Articles

Incorporation of Ebola glycoprotein into HIV particles facilitates dendritic cell and macrophage targeting and enhances HIV-specific immune responses.

The development of an effective vaccine against HIV infection remains a global priority. Dendritic cell (DC)-based HIV immunotherapeutic vaccine is a promising approach which aims at optimizing the HIV-specific immune response using primed DCs to promote and enhance both the cellular and humoral arms of immunity. Since the Ebola virus envelope glycoprotein (EboGP) has strong DC-targeting ability, we investigated whether EboGP is able to direct HIV particles towards DCs efficiently and promote potent HIV-specific immune responses. Our results indicate that the incorporation of EboGP into non-replicating virus-like particles (VLPs) enhances their ability to target human monocyte-derived dendritic cells (MDDCs) and monocyte-derived macrophages (MDMs). Also, a mucin-like domain deleted EboGP (EboGPΔM) can further enhanced the MDDCs and MDMs-targeting ability. Furthermore, we investigated the effect of EboGP on HIV immunogenicity in mice, and the results revealed a significantly stronger HIV-specific humoral immune response when immunized with EboGP-pseudotyped HIV VLPs compared with those immunized with HIV VLPs. Splenocytes harvested from mice immunized with EboGP-pseudotyped HIV VLPs secreted increased levels of macrophage inflammatory proteins-1α (MIP-1α) and IL-4 upon stimulation with HIV Env and/or Gag peptides compared with those harvested from mice immunized with HIV VLPs. Collectively, this study provides evidence for the first time that the incorporation of EboGP in HIV VLPs can facilitate DC and macrophage targeting and induce more potent immune responses against HIV.

The Long Pentraxin PTX3 as a Link Between Innate Immunity, Tissue Remodeling, and Cancer.

The innate immune system comprises a cellular and a humoral arm. Humoral pattern recognition molecules include complement components, collectins, ficolins, and pentraxins. These molecules are involved in innate immune responses by recognizing microbial moieties and damaged tissues, activating complement, exerting opsonic activity and facilitating phagocytosis, and regulating inflammation. The long pentraxin PTX3 is a prototypic humoral pattern recognition molecule that, in addition to providing defense against infectious agents, plays several functions in tissue repair and regulation of cancer-related inflammation. Characterization of the PTX3 molecular structure and biochemical properties, and insights into its interactome and multiple roles in tissue damage and remodeling support the view that microbial and matrix recognition are evolutionarily conserved functions of humoral innate immunity molecules.

Innate immunity, inflammation and tumour progression: double-edged swords.

Components of the cellular and the humoral arm ofthe immune system are essential elements of thetumour microenvironment (TME). The TME includes tumour-associated macrophages which have served as a paradigm for the cancer-promoting inflammation. Cytokines, IL-1 in particular, and complement have emerged as important players in tumour promotion. On the other hand, myeloid cells, innate lymphoid cells and complement have the potential, if unleashed, to mediate anticancer resistance. Targeting checkpoints restraining innate immunity, macrophages and natural killer (NK) cells in particular holds promise as a therapeutic strategy.

Characterizing the B-Cell and Humoral Response in Tertiary Lymphoid Organs in Kidney Allografts.

Tertiary lymphoid organs are formed at sites of chronic inflammation and are thought to contribute to the immune response. Here, we aimed to characterize the structure and function of tertiary lymphoid organs in a model of murine kidney allotransplant to understand their role in alloimmunity. We transplanted 4 C57BL/6 mouse kidneys (isograft group) and 17 DBA/2 mouse kidneys into C57BL/6 mouse recipients. Three DBA/2-to-C57BL/6 transplant mice that rejected their grafts acutely (before 10 days posttransplant) were excluded from the study. The 14 surviving DAB2 grafts were retrieved at day 45 posttransplant and evaluated histologically. The presence of antibody-secreting cells and circulating levels of donor-specific antibodies were also evaluated. We found that tertiary lymphoid organs can be associated with a beneficial response in a kidney allotransplant model. Characterization of B-cell subsets within tertiary lymphoid organs in mouse kidney allografts revealed naive, plasma, and memory B cells, which were mostly grouped within or in close proximity of tertiary lymphoid organs. Staining for intracellular immunoglobulin G showed that many of the B cells within tertiary lymphoid organs were capable of producing antibodies. Although allospecific antibodies were found in the serum of recipient mice and were deposited in the transplanted kidneys, graft function was not affected in this model. B cells within tertiary lymphoid organs are functional and contribute to the humoral arm of the alloresponse. However, tertiary lymphoid organs are not necessarily associated with graft rejection, suggesting that protective mechanisms are at play.

T follicular helper cell heterogeneity: Time, space, and function.

T follicular helper (Tfh) cells play a crucial role in orchestrating the humoral arm of adaptive immune responses. Mature Tfh cells localize to follicles in secondary lymphoid organs (SLOs) where they provide help to B cells in germinal centers (GCs) to facilitate immunoglobulin affinity maturation, class-switch recombination, and generation of long-lived plasma cells and memory B cells. Beyond the canonical GC Tfh cells, it has been increasingly appreciated that the Tfh phenotype is highly diverse and dynamic. As naive CD4+ T cells progressively differentiate into Tfh cells, they migrate through a variety of microanatomical locations to obtain signals from other cell types, which in turn alters their phenotypic and functional profiles. We herein review the heterogeneity of Tfh cells marked by the dynamic phenotypic changes accompanying their developmental program. Focusing on the various locations where Tfh and Tfh-like cells are found, we highlight their diverse states of differentiation. Recognition of Tfh cell heterogeneity has important implications for understanding the nature of T helper cell identity specification, especially the plasticity of the Tfh cells and their ontogeny as related to conventional T helper subsets.

Detecting donor-specific antibodies: the importance of sorting the wheat from the chaff.

Human leukocyte antigen (HLA) compatibility is very important for successful transplantation of solid organs. In this paper, we focused on the humoral arm of immunity in the clinical setting of organ transplantation: how HLA antibodies develop, how they can be detected, and what they can do to injure organ transplants. Specifically, we explore the technical perspectives of detecting donor-specific antibodies (DSA) in HLA laboratories, and use real-life clinical cases to explain the principles. Currently there are many tools in our HLA antibody detection toolbox: conventional cytotoxicity cross match, flow cross match, and solid phase assays using beads conjugated with single or multiple HLA antigens. Single antigen bead (SAB) assay is the most sensitive tool available for detecting HLA antibodies and assessing the immunological risk for organ transplant. However, there are intrinsic limitations to solid-phase assays and they are prone to both false negativity and importantly, false positivity. Denatured antigens on single antigen beads might be the most prominent source of false positive reactivity, and may have been underestimated by many HLA experts. No single assay is perfect and therefore multiple methods, including the less sensitive assays, should be employed to determine the clinical relevance of detected HLA antibodies. Thoughtful process, including knowledge of HLA systems, cross reactivity, epitopes, and the patient's clinical history should be employed to correctly interpret data. The clinical team should work closely with HLA laboratories to ensure accurate interpretation of information and optimal management of patients before and after organ transplantation.

Role of a fluid-phase PRR in fighting an intracellular pathogen: PTX3 in Shigella infection.

Shigella spp. are pathogenic bacteria that cause bacillary dysentery in humans by invading the colonic and rectal mucosa where they induce dramatic inflammation. Here, we have analyzed the role of the soluble PRR Pentraxin 3 (PTX3), a key component of the humoral arm of innate immunity. Mice that had been intranasally infected with S. flexneri were rescued from death by treatment with recombinant PTX3. In vitro PTX3 exerts the antibacterial activity against Shigella, impairing epithelial cell invasion and contributing to the bactericidal activity of serum.PTX3 is produced upon LPS-TLR4 stimulation in accordance with the lipid A structure of Shigella. In the plasma of infected patients, the level of PTX3 amount only correlates strongly with symptom severity. These results signal PTX3 as a novel player in Shigella pathogenesis and its potential role in fighting shigellosis. Finally, we suggest that the plasma level of PTX3 in shigellosis patients could act as a biomarker for infection severity.

Immune and Genetic Features of the Chromosome 22q11.2 Deletion (DiGeorge Syndrome).

This review provides an update on the progress in identifying the range of immunological dysfunction seen in DiGeorge syndrome and on more recent diagnostic and treatment approaches. Clinically, the associated thymic hypoplasia/aplasia is well known and can have profound effects on T cell function. Further, the humoral arm of the immune system can be affected, with hypogammaglobulinemia and poor vaccine-specific antibody response. Additionally, genetic testing utilizing chromosomal microarray demonstrates a small but significant number of 22q11 deletions that are not detectable by standard FISH testing. The recent addition of a TREC assay to newborn screening can identify a subset of infants whose severe immune defects may result from 22q11 deletion. This initial presentation now also places the immunologist in the role of "first responder" with regard to diagnosis and management of these patients. DiGeorge syndrome reflects a clinical phenotype now recognized by its underlying genetic diagnosis, chromosome 22q11.2 deletion syndrome, which is associated with multisystem involvement and variable immune defects among patients. Updated genetic and molecular techniques now allow for earlier identification of immune defects and confirmatory diagnoses, in this disorder with life-long clinical issues.

Immunological Oral Health Status of the Poultry Plants Employees

Summary. Study of periodontal diseases gives us grounds for making a generalized conclusion that an appearance of abnormal changes in tissues holding teeth takes place on change of overall health and as a result of the influence of a set of internal and external factors, which define an approach to the treatment and prevention of these diseases. Despite automation and mechanization of poultry plants, much more poultry plants employees are influenced by adverse factors of production that leads to occupational diseases, partially to periodontal diseases.
 The aim of the work – to investigate a condition of the local nonspecific immunity among poultry plants employees having periodontal diseases.
 Materials and Methods. In research 50 poultry breeders having generalized periodontitis, who made a basic group, and 20 persons with generalized periodontitis forming a comparison group, who were not in contact with birds, took part. Findings were compared with data of 20 somatically healthy persons from the control group. In order to study a condition of the local resistance at generalized periodontitis under the influence of harmful factors of poultry production, certain immunity factors of capillary blood of gums and oral fluid were examined: IgM, IgG, IgA, SIgA, phagocytic index (PhI) and phagocytic number (PhN). The most significant changes in the local nonspecific protection factors were found among patients of the basic group: content of serum IgA was significantly below normal: (1.82±0.11) g/l. Increase in production of IgМ and IgG at decreasing content of IgA among persons from the basic group was indicative of functional tension of immunity humoral arm on antigen stimulation with streptococcal infection. A significant deficiency of SIgA in oral fluid (0.62±0.03) g/l) was detected that was two times less than values of the control group and by 1.3 less than in the comparison group. Phagocytosis percent, phagocytic number, and phagocytic index among the patients of the basic group were much higher comparing with the comparison and control groups. That was indicative of decrease in appropriate immune response among them. Thus, the findings have shown that permanent immunodysfunctions among the poultry plants employees having generalized periodontitis are increasing under the influence of the occupational pathogens related to poultry production.

The long pentraxin 3 (PTX3) plays a key role in the immunomodulation of diet induced-obesity in mice

Aim: Chronic low-grade inflammation characterizes metabolic syndrome. Our aim was to study the role of PTX3, an essential component of the humoral arm of innate immunity, during HFD induced-obesity.

Abstract 615: Increased somatic hypermutation in the immunoglobulin sequences of melanoma patients who have durable response to checkpoint inhibitor therapy

Abstract Patient immune response to tumor can drive profound and durable clinical benefit, but the contribution of antibodies to this benefit is poorly understood. To further our understanding of the role of the humoral response, we compared antibody sequence repertoires of durable responder and non-responder melanoma patients before and during checkpoint inhibitor treatment. We collected pre- and on-treatment peripheral blood from 26 melanoma patients treated with pembrolizumab (9), ipilimumab (8) or nivolumab+ipilimumab (9). Of the 26 patients, 14 were durable responders (RECIST stable disease, partial response, or complete response for at least 6 months) and 12 were non-responders. We generated natively paired heavy and light chain antibody sequences from individual IgG plasmablasts (CD19+CD20-CD38+CD3-CD14-IgA-IgM-IgD-). Sequences were obtained from a total of 26,725 plasmablasts. These sequences were used to reconstruct lineages (sets of plasmablasts likely derived from a common progenitor B cell) where each lineage shares heavy and light V genes, CDR3 length and 80% sequence similarity in CDR3s. Durable responders exhibited an increase in somatic hypermutation (SHM) after initiation of treatment. In contrast, no significant change in SHM was observed in non-responders. Higher SHM was also observed in on-treatment repertoires of responders compared with those of non-responders suggesting that T cell checkpoint inhibitors promote activation of humoral immunity in clinical responders. Furthermore, persistent antibody lineages (observed both before and during treatment) showed higher SHM than lineages observed at only a single time point. Comparison of lineages between patients identified antibodies with high sequence similarity suggesting these antibodies may have arisen from convergent selection, i.e., different patients raising antibodies against shared or similar epitopes. These putative convergent antibodies were enriched in IgG2. IgG2 usage was also higher overall in durable responders than non-responders, even in samples taken prior to treatment. The higher levels of IgG2 observed in responders and in the potentially convergent sets of antibodies suggest that IgG2 antibodies may play a role in effective anti-tumor responses. In conclusion, our analysis of plasmablast repertoires from melanoma patients suggests that treatment with checkpoint inhibitors promotes SHM in durable responders, and that responder plasmablasts are enriched in IgG2. Moreover, patients make potentially convergent antibodies that are also enriched for the IgG2 subclass. Our observations demonstrate that the humoral immune response is remodeled in patients with anti-tumor responses and support a role for the humoral arm of the immune response in driving clinical benefit in patients treated with checkpoint inhibitors. Citation Format: Ngan Nguyen, Alusha Mamchak, Mariano Severgnini, Kevin S. Williamson, Xinqi Wu, Elliott F. Drabek, Michael Manos, Xiaomu Chen, Xiaobin Tang, Zoe Amiri, Chantia Carroll, Yvonne Leung, Dongkyoon Kim, Wayne Volkmuth, Norman Greenberg, Daniel Emerling, William H. Robinson, Guy Cavet, F. Stephen Hodi. Increased somatic hypermutation in the immunoglobulin sequences of melanoma patients who have durable response to checkpoint inhibitor therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 615.

The Florida manatee (Trichechus manatus latirostris) T cell receptor loci exhibit V segment locus synteny and chain-specific evolution

Abstract Manatees are a vulnerable, charismatic sentinel species from the evolutionarily divergent order Afrotheria. We have previously described the immunoglobulin heavy chain locus of the Florida manatee (Trichechus manatus latirostris) and found limited antigen receptor diversity in this humoral arm of the adaptive immune system. We therefore investigated the antigen receptor loci of the cellular arm: the T cell receptor. Manatees are the first species from either Afrotheria or Xenarthra, the most basal eutherian taxonomic groups, to have an in-depth characterization of all T cell receptor loci and expressed repertoires. We manually annotated the three TR loci on the T. m. latirostris genomic scaffolds using BLAST and RSSsite, and compared the segments and overall genomic organization to the human TR loci. We identified the human V segment subgroups that are conserved in T. m. latirostris and found that TRADV are most conserved, TRBV are moderately conserved, and TRGV are the least conserved. The V segment order in the TRAD and TRB loci also showed synteny between the two species. The TRAD locus had five V segment subgroup synteny blocks that showed long-range duplications in the T. m. latirostris locus. The TRB locus had three V segment subgroup synteny blocks that showed short-range duplications. The conservation of V segment sequence and order correlated to the locus complexity, emphasizing the role of genomic organization on gene evolution. We also identified evidence for a VHδ pseudogene for the first time in a eutherian mammal. These novel findings underline the value of including species within the basal radiation of eutherian evolution in comparative studies.

PTX3, a Humoral Pattern Recognition Molecule, in Innate Immunity, Tissue Repair, and Cancer.

Innate immunity includes a cellular and a humoral arm. PTX3 is a fluid-phase pattern recognition molecule conserved in evolution which acts as a key component of humoral innate immunity in infections of fungal, bacterial, and viral origin. PTX3 binds conserved microbial structures and self-components under conditions of inflammation and activates effector functions (complement, phagocytosis). Moreover, it has a complex regulatory role in inflammation, such as ischemia/reperfusion injury and cancer-related inflammation, as well as in extracellular matrix organization and remodeling, with profound implications in physiology and pathology. Finally, PTX3 acts as an extrinsic oncosuppressor gene by taming tumor-promoting inflammation in murine and selected human tumors. Thus evidence suggests that PTX3 is a key homeostatic component at the crossroad of innate immunity, inflammation, tissue repair, and cancer. Dissecting the complexity of PTX3 pathophysiology and human genetics paves the way to diagnostic and therapeutic exploitation.

Bone marrow PDGFRα+Sca-1+-enriched mesenchymal stem cells support survival of and antibody production by plasma cells in vitro through IL-6.

Plasma cells (PCs) acquiring long lifespans in the bone marrow (BM) play a pivotal role in the humoral arm of immunological memory. The PCs reside in a special BM niche and produce antibodies against past-encountered pathogens or vaccine components for a long time. In BM, cysteine-X-cysteine (CXC) chemokine receptor type 4 (CXCR4)-expressing PCs and myeloid cells such as dendritic cells are attracted to and held by CXC chemokine ligand 12 (CXCR12)-secreting stromal cells, where survival of the PCs is supported by soluble factors such as IL-6 and APRIL (a proliferation-inducing ligand) produced by neighboring myeloid cells. Although these stromal cells are also supposed to be involved in the support of the survival and antibody production, the full molecular mechanism has not been clarified yet. Here, we show that BM PDGFRα+Sca-1+-enriched mesenchymal stem cells (MSCs), which can contribute as stromal cells for hematopoietic stem cells, also support in vitro survival of and antibody production by BM PCs. IL-6 produced by MSCs was found to be involved in the support. Immunohistochemistry of BM sections suggested a co-localization of a minor population of PCs with PDGFRα+Sca-1+ MSCs in the BM. We also found that the sort-purified MSC preparation was composed of multiple cell groups with different gene expression profiles, as found on single-cell RNA sequencing, to which multiple roles in the in vitro PC support could be attributed.

B cells in health and disease

B lymphocytes are part of the adaptive immune system and responsible for the humoral arm of it. While the main task during early development is the production of a broad repertoire of naïve B cells, during further differentiation in the periphery the main task changes to the selection of the best fitting immunoglobulin producing B cell and its long-term survival. The homeostasis of this system is fine-tuned and reveals an age dependent balance between the different B-cell populations. The physiologic development and homeostasis is often disturbed in patients with immunodeficiency or autoimmunity. In this presentation, I will discuss the normal homeostasis of B cells and its analysis by flow cytometry. I will present altered B cell homeostasis in examples of patients with genetically defined and non-defined immunodeficiencies and autoimmune disorders and discuss the research, diagnostic and clinical value of the information we can draw from these findings.

Pentraxin 3 and biopsy status in celiac patients.

In our study we explored a possible relationship between PTX3 and CD. Gluten sensitivity is known as a hallmark of celiac disease (CD). The diagnosis of CD requires demonstration of a typical enteropathy, and positive serology supports the diagnosis. The CD immune response involves the adaptive, as well as the innate immunity and is characterized by the presence of anti-gliadin (AGA) and anti-transglutaminase 2 antibodies (tTGA), lymphocytic infiltration in the intestinal epithelial membrane and expression of multiple cytokines. The long pentraxin 3 (PTX3), an acute-phase inflammatory molecule, plays an important role in innate immunity. 108 CD patients were divided according to Marsh Histological grade following Marsh criteria classification in three groups: Group 1: Marsh 0, patients with a known history of CD under gluten free diet, complete remission; Group 2: Marsh1 and Marsh 2; Group 3: Marsh 3. Healthy age-matched controls without a known history of CD or gastrointestinal symptoms (n=30) served as controls. PTX3 serum levels were measured by sandwich ELISA on an automated platform. PTX3 serum levels were significantly elevated in group 3 and group 2 compared with HC (mean 3.31± 1.27 ng/mL and 3.97 ± 0.54 ng/mL versus 1.06 ± 0.59 ng/mL; P < 0.005), with group 1 (0.76±0.31 ng/mL). No statistically significant differences were found between group 1 and HC group. We found a strong linear correlation between PTX3 serum levels and AGA levels in group 2 (r=0.78, P <0.0001), and group 3 (r =0.63, P < 0.005) but no correlations were detected between PTX3 serum levels and tTGA levels (group 2, r= 0.04; group 3, r=0.24). Serological data revealed that PTX3 correlated with major gastrointestinal damage patients. PTX3 is a component of the humoral arm of the innate immune system. Our data showed that PTX3 serum levels were high in active disease patients with pathological levels of AGA. We also demonstrated that patients with normal AGA IgA levels had PTX3 serum levels compared to healthy control. We hypothesized that PTX3 is able to modulate the innate response to gliadin in CD and it could regulate the adaptive immune response.

Beyond immunity: The Imd pathway as a coordinator of host defense, organismal physiology and behavior

The humoral arm of host defense in Drosophila relies on two evolutionarily conserved NFκB signaling cascades, the Toll and the immune deficiency (Imd) pathways. The Imd signaling pathway senses and neutralizes Gram-negative bacteria. Its activity is tightly adjusted, allowing the host to simultaneously prevent infection by pathogenic bacteria and tolerate beneficial gut microbiota. Over-activation of Imd signaling is detrimental at least in part by causing gut dysbiosis that further exacerbates intestinal pathologies. Furthermore, it is increasingly recognized that the Imd pathway or its components also play non-immune roles. In this review, we summarize recent advances in Imd signal transduction, discuss the gut-microbiota interactions mediated by Imd signaling, and finally elaborate on its diverse physiological functions beyond immunity. Understanding the multifaceted physiological outputs of Imd activation will help integrate its immune role into the regulation of whole organismal physiology.

Preoperative methylprednisolone increases plasma Pentraxin 3 early after total knee arthroplasty: a randomized, double-blind, placebo-controlled trial.

Preoperative glucocorticoid administration reduces the systemic inflammatory response. Pentraxin 3 (PTX3) is a novel inflammatory marker belonging to the humoral arm of innate immunity exerting a potentially protective host response. This study evaluated PTX3 and other complement marker changes after preoperative methylprednisolone (MP) early after total knee arthroplasty (TKA). Seventy patients were randomized (1:1) to preoperative intravenous (i.v.) MP 125 mg (group MP) or isotonic saline i.v. (group C). The outcomes included change in plasma PTX3, mannose-binding lectin (MBL), ficolins (ficolin-1, -2 and -3), complement components (C4 and C3), terminal complement complex (TCC) and C-reactive protein (CRP) concentrations. Blood samples were analysed at baseline and 2, 6, 24 and 48 h after surgery with complete sampling from 63 patients for analyses. MP resulted in an increase in circulating PTX3 compared to saline from baseline to 24 h postoperatively (P < 0·001), while MP reduced the systemic inflammatory response (CRP) 24 and 48 h postoperatively (P < 0·001). However, the small postoperative changes in MBL, ficolin-1, -2 and -3, C4, C3 and TCC concentrations did not differ between groups (P > 0·05). In conclusion, preoperative MP 125 mg increased circulating PTX3 and reduced the general inflammatory response (CRP) early after TKA, but did not affect other complement markers.

Collectins in urinary tract and kidney diseases.

The innate immune system serves as the frontline defense against invading pathogens and initiates an inflammatory response to microorganisms. Collectins are C-type lectins that are structurally characterized by a collagen-like sequence and a carbohydrate recognition domain. Moreover, they are widely expressed throughout the body and are involved in the innate immunity against a variety of pathogens, regulating inflammation, and protecting the lungs from pathogens. Recently, two classical collectins, surfactant protein A (SP-A) and surfactant protein D (SP-D), as well as novel collectin 11, were found present in urinary tract tissues. They are increasingly recognized as key players in activating the humoral arm of innate immunity and host defense in urinary tract and kidney diseases, although their biological features, functions, and mechanisms in this regard remain largely unclear. In this review, we aim to integrate results reported by ourselves and others to summarize and gain a better understanding of the functions of collectins (SP-A, SP-D, and collectin 11) in urinary tract and kidney diseases.

Thioester-containing proteins regulate the Toll pathway and play a role in Drosophila defence against microbial pathogens and parasitoid wasps

BackgroundMembers of the thioester-containing protein (TEP) family contribute to host defence in both insects and mammals. However, their role in the immune response of Drosophila is elusive. In this study, we address the role of TEPs in Drosophila immunity by generating a mutant fly line, referred to as TEPqΔ, lacking the four immune-inducible TEPs, TEP1, 2, 3 and 4.ResultsSurvival analyses with TEPqΔ flies reveal the importance of these proteins in defence against entomopathogenic fungi, Gram-positive bacteria and parasitoid wasps. Our results confirm that TEPs are required for efficient phagocytosis of bacteria, notably for the two Gram-positive species tested, Staphylococcus aureus and Enterococcus faecalis. Furthermore, we show that TEPqΔ flies have reduced Toll pathway activation upon microbial infection, resulting in lower expression of antimicrobial peptide genes. Epistatic analyses suggest that TEPs function upstream or independently of the serine protease ModSP at an initial stage of Toll pathway activation.ConclusionsCollectively, our study brings new insights into the role of TEPs in insect immunity. It reveals that TEPs participate in both humoral and cellular arms of immune response in Drosophila. In particular, it shows the importance of TEPs in defence against Gram-positive bacteria and entomopathogenic fungi, notably by promoting Toll pathway activation.