Innate IFN-gamma production by subsets of natural killer cells, natural killer T cells and gammadelta T cells in response to dying bacterial-infected macrophages

Classification and function of γδT cells and its research progress in anti-glioblastoma

Human peripheral blood T lymphocytes are classified into alpha-beta T (αβΤ) cells and gamma-delta T (γδΤ) cells based on the difference in T cell receptors (TCRs). αβT cells are crucial for the acquired immune response, while γδΤ cells, though only a small subset, can recognize antigenic substances. These antigens do not need to be processed and presented and are not restricted by MHC. This distinguishes γδΤ cells from αβT cells and highlights their distinct role in innate immunity. Despite their small number, γδΤ cells hold significant significance in anti-tumor, anti-infection and immune regulation. Glioblastoma (GBM) represents one of the most prevalent malignant tumors within the central nervous system (CNS). Surgical resection alone proves to be an ineffective method for curing this type of cancer. Even with the combination of surgical resection, radiotherapy, and chemotherapy, the prognosis of some individuals with glioblastoma is still poor, and the recurrence rate is high. In this research, the classification, biological, and immunological functions of γδT cells and their research progress in anti-glioblastoma were reviewed.

Understanding Ocular Surface Inflammation in Tears Before and After Autologous Cultivated Limbal Epithelial Stem Cell Transplantation

INTRODUCTION

We aimed to determine the expression of inflammatory cytokines in the tears of patients with unilateral total limbal stem cell deficiency (TLSCD) caused by chemical burns before and after autologous cultivated limbal epithelial stem cell transplantation (CLET).

METHODS

Tear samples were collected from both eyes of 23 patients with unilateral TLSCD and 11 healthy controls, at fixed timepoints before and after CLET. Dissolved molecules were extracted from Schirmer's strips using a standardised method and analysed on an array plate of ten inflammatory cytokines (V-Plex Proinflammatory Panel 1 Human Kit, MSD).

RESULTS

IL1β expression was significantly elevated in the TLSCD eye compared with the unaffected eye at baseline (p < 0.0001) but decreased to normal 3 months post-CLET (p = 0.22). IL6 and IL8 were unaffected at baseline but significantly elevated in the TLSCD eyes at 1 month post-CLET (p = 0.001 and p < 0.0001, respectively). IL6 returned to normal at 3 months and IL8 at 6 months post-CLET. There was a significant renewed increase in IL1β, IL6 and IL8 expression at 12 months post-CLET (p < 0.0001, p = 0.0001 and p = 0.0003, respectively). IFNγ, IL10 and IL12p70 expression were significantly reduced in both eyes of patients with unilateral TLSCD at all timepoints.

CONCLUSION

IL1β is a specific marker of inflammation in TLSCD eyes that could be therapeutically targeted pre-CLET to improve stem cell engraftment. At 12 months post-CLET the spike in levels of IL1β, IL6 and IL8 coincides with cessation of topical steroids, suggesting ongoing subclinical inflammation. We therefore recommend not discontinuing topical steroid treatment in cases where penetrating keratoplasty is indicated; however, further investigation is needed to ascertain this.

TRIAL REGISTRATION

European Union Drug Regulating Authorities Clinical Trials Database (EuDRACT 2011-000608-16); ISRCTN (International Standard Randomised Controlled Trial Number (isrctn51772481).

Immunometabolism in human brucellosis: An emerging field of investigation

In recent years, extreme attention has been focused on the role of immunometabolism in the regulation of immune cell responses in healthy individuals during infection, autoimmunity, and cancer. In the infection biology area, it has been shown that there is a close relationship between the immune system and the host metabolic changes. Brucella species is an intracellular coccobacillus that infects humans and mammals, which led to brucellosis. Brucella species with host-specific evolutionary mechanisms allow it to hide from or manipulate cellular immunity and achieve intracellular persistence. Intracellular bacterial pathogens such as Brucella species also employ host cell resources to replicate and persist inside the host. Targeting these host systems is one promising strategy for developing novel antimicrobials to tackle intracellular infections. This study will summarize the role of metabolic reprogramming in immune cells and their relationship to brucellosis.

Planktonic and Biofilm-Associated Pseudomonas aeruginosa and Staphylococcus epidermidis Elicit Differential Human Peripheral Blood Cell Responses

Despite the considerable progress made in recent years, our understanding of the human immune response to microbial biofilms is still poor. The aim of the present study was to compare the in vitro response of human peripheral blood mononuclear cells (PBMC) to biofilms and planktonic cells of Pseudomonas aeruginosa and Staphylococcus epidermidis, two bacterial species particularly relevant in patients with cystic fibrosis or undergoing endovascular catheterization, respectively. PBMC isolated from healthy donors were co-cultured with 24 h-old biofilms or with exponentially growing cells of both species. Following 24 h of co-culture, the expression of early activation markers and the levels of cytokines in the culture supernatants were assessed by flow cytometry, while biofilm biomass and architecture were evaluated by crystal violet staining, CFU count, and confocal microscopy. Around 20% of PBMC was activated in response to both biofilms and planktonic cells of P. aeruginosa. In contrast, planktonic cells of S. epidermidis induced a statistically higher degree of activation than their biofilm counterpart (25% versus 15%; p < 0.01). P. aeruginosa biofilms stimulated pro-inflammatory (TNF-α, IL-1β, IFN-γ, and IL-6) and anti-inflammatory (IL-10) cytokine production at statistically significant levels higher than its planktonic counterpart, while an opposite trend was observed with S. epidermidis. Differences in the architecture of the biofilms and in the number of PBMC infiltrating the biofilms between the two bacterial species may at least partially explain these findings. Collectively, the results obtained highlighted marked differences in the host–cell response depending on the species and the mode of growth (biofilms versus planktonic cultures), allowing speculations on the different strategies adopted by P. aeruginosa and S. epidermidis to persist in the host during the course of chronic infections.

Capacity of two Staphylococcus aureus strains with different adaptation genotypes to persist and induce damage in bovine mammary epithelial cells and to activate macrophages

The aim of this study was to evaluate and compare the ability to adhere/internalize, persist, and induce damage in mammary epithelial cells (MAC-T) of two Staphylococcus aureus strains with different adaptation genotypes (low and high) to the bovine mammary gland (MG). Also, the phagocytic and bactericidal capacity induced after the interaction between macrophages, isolated from mammary secretion, of both S. aureus strains was evaluated. Two isolates (designated 806 and 5011) from bovine intramammary infection (IMI) harboring genes involved in adherence and biofilm production, belonging to different capsular polysaccharide (CP) type, accessory gene regulator (agr) group, pulsotype (PT) and sequence type/clonal complex (ST/CC). Strains 806 and 5011 were associated with low (nonpersistent-NP) and high (persistent-P) adaptation to the MG, respectively. Strain 5011 (P), agr group I, cap8 positive and strong biofilm producer showed higher capacity to adhere/internalize in MAC-T compared with strain 806 (NP), characterized as agr group II, cap5 positive and weak biofilm producer. Strain 5011(P) could be recovered from MAC-T lysates up to 72 h pi; while strain 806 (NP) could be recovered only at 4 h pi. Strain 5011 (P) showed greater capacity to induce apoptosis compared with strain 806 (NP) at 4, 24 and 48 h pi. Macrophages infected with strain 5011 (P) showed a greater phagocytic capacity and higher percentage of intracellular reactive oxygen species (ROS) production than strain 806 (NP). No viable bacteria were isolated from macrophages lysates stimulated with any of the S. aureus strains at 2, 4, 8 and 24 h pi. The knowledge of the molecular profile of the S. aureus strains causing bovine mastitis in a herd could become a tool to expose the most prevalent virulence gene patterns and advance in the elucidation of the pathogenesis of chronic mastitis.

Artificial Natural Killer Cells for Specific Tumor Inhibition and Renegade Macrophage Re-Education

Natural killer (NK) cells can not only recognize and eliminate abnormal cells but also recruit and re-educate immune cells to protect the host. However, the functions of NK cells are often limited in the immunosuppressive tumor microenvironment (TME). Here, artificial NK cells (designated as aNK) with minor limitations of TME for specific tumor killing and renegade macrophage re-education are created. The red blood cell membrane (RBCM) cloaks perfluorohexane (PFC) and glucose oxidase (GOX) to construct the aNK. The aNK can directly kill tumor cells by exhausting glucose and generating hydrogen peroxide (H₂ O₂ ). The generated H₂ O₂ is also similar to cytokines and chemokines for recruiting immune cells and re-educating survived macrophages to attack tumor cells. In addition, the oxygen-carried PFC can strengthen the catalytic reaction of GOX and normalize the hypoxic TME. In vitro and in vivo experiments display that aNK with slight TME limitations exhibit efficient tumor inhibition and immune activation. The aNK will provide a new sight to treat tumor as the supplement of aggressive NK cells.

Circulating Th1, Th2, Th17, Treg, and PD-1 Levels in Patients with Brucellosis

Brucella is an intracellular infection bacterium; the pathogenesis of Brucella and chronicity of infection may be related to the immune response of T cells. T lymphocytes mainly participate in cellular immune response. The extent of different T cell subsets imbalanced and their function dysregulated in patients with brucellosis remain not explicit. We grouped patients at different stages (acute, chronic, and convalescent). The frequencies of Th1, Th2, Th17, Treg, and PD-1 (programmed cell death protein 1) in peripheral blood were examined by flow cytometry, and the expressions of T lymphocyte cytokines in serum were detected by cytometric bead array. Th1, Th17, and Treg cell immunity was predominant in the acute stage, while Th2, Th17, and Treg cell immunity was predominant in the chronic stage. The expressions of PD-1 on CD4+ and CD8+ T lymphocytes were significantly different in acute and chronic patients. The percentages of Th1 cells in convalescent patients were still higher than those in healthy controls within one year after withdrawal. The expression of T lymphocyte cytokines in serum was different in patients at different stages. These results indicate that peripheral T lymphocyte immunity was involved in patients with brucellosis and represents a target for the preclinical and clinical assessment of novel immunomodulating therapeutics. The patients' immune function had not completely recovered in a short period of time during convalescence, so long-term follow-up of convalescent patients is needed.

Myeloid and T Cell-Derived TNF Protects against Central Nervous System Tuberculosis

Tuberculosis of the central nervous system (CNS-TB) is a devastating complication of tuberculosis, and tumor necrosis factor (TNF) is crucial for innate immunity and controlling the infection. TNF is produced by many cell types upon activation, in particularly the myeloid and T cells during neuroinflammation. Here we used mice with TNF ablation targeted to myeloid and T cell (MT-TNF^-/-) to assess the contribution of myeloid and T cell-derived TNF in immune responses during CNS-TB. These mice exhibited impaired innate immunity and high susceptibility to cerebral Mycobacterium tuberculosis infection, a similar phenotype to complete TNF-deficient mice. Further, MT-TNF^-/- mice were not able to control T cell responses and cytokine/chemokine production. Thus, our data suggested that collective TNF production by both myeloid and T cells are required to provide overall protective immunity against CNS-TB infection.

The influence of age on Campylobacter jejuni infection in chicken

Campylobacter jejuni (C. jejuni)-host-interaction may be affected by the maturation stage of the chicken's immune system and the developing gut microbiota composition. We compared these parameters between birds C. jejuni-inoculated at day one, 10, 22 and 31 post hatch. The highest C. jejuni-colonization rate and numbers of colony forming units (CFU) were detected in caecal content of day-one-inoculated birds while the lowest was detected in 22-days-old birds. The low bacterial colonization of 22-days-old chickens correlated with the most prominent immune reactions in this age group in comparison to other age groups. Age and C. jejuni-inoculation had a significant effect on lymphocyte numbers and cytokine expression levels in caecum as well as on gut flora composition. Overall, the immune response to C. jejuni is significantly influenced by the age of the infected chickens leading to differences in C. jejuni-colonization pattern between age goups.

T Cell Intrinsic USP15 Deficiency Promotes Excessive IFN-γ Production and an Immunosuppressive Tumor Microenvironment in MCA-Induced Fibrosarcoma

USP15 is a deubiquitinase that negatively regulates activation of naive CD4(+) T cells and generation of IFN-γ-producing T helper 1 (Th1) cells. USP15 deficiency in mice promotes antitumor T cell responses in a transplantable cancer model; however, it has remained unclear how deregulated T cell activation impacts primary tumor development during the prolonged interplay between tumors and the immune system. Here, we find that the USP15-deficient mice are hypersensitive to methylcholantrene (MCA)-induced fibrosarcomas. Excessive IFN-γ production in USP15-deficient mice promotes expression of the immunosuppressive molecule PD-L1 and the chemokine CXCL12, causing accumulation of T-bet(+) regulatory T cells and CD11b(+)Gr-1(+) myeloid-derived suppressor cells at tumor site. Mixed bone marrow adoptive transfer studies further reveals a T cell-intrinsic role for USP15 in regulating IFN-γ production and tumor development. These findings suggest that T cell intrinsic USP15 deficiency causes excessive production of IFN-γ, which promotes an immunosuppressive tumor microenvironment during MCA-induced primary tumorigenesis.

Inability to sustain intraphagolysosomal killing of Staphylococcus aureus predisposes to bacterial persistence in macrophages

Macrophages are critical effectors of the early innate response to bacteria in tissues. Phagocytosis and killing of bacteria are interrelated functions essential for bacterial clearance but the rate-limiting step when macrophages are challenged with large numbers of the major medical pathogen Staphylococcus aureus is unknown. We show that macrophages have a finite capacity for intracellular killing and fail to match sustained phagocytosis with sustained microbial killing when exposed to large inocula of S. aureus (Newman, SH1000 and USA300 strains). S. aureus ingestion by macrophages is associated with a rapid decline in bacterial viability immediately after phagocytosis. However, not all bacteria are killed in the phagolysosome, and we demonstrate reduced acidification of the phagolysosome, associated with failure of phagolysosomal maturation and reduced activation of cathepsin D. This results in accumulation of viable intracellular bacteria in macrophages. We show macrophages fail to engage apoptosis-associated bacterial killing. Ultittop mately macrophages with viable bacteria undergo cell lysis, and viable bacteria are released and can be internalized by other macrophages. We show that cycles of lysis and reuptake maintain a pool of viable intracellular bacteria over time when killing is overwhelmed and demonstrate intracellular persistence in alveolar macrophages in the lungs in a murine model.

Natural Killer Cells Mediate Protection against Yersinia pseudotuberculosis in the Mesenteric Lymph Nodes

Natural killer cells play a crucial role in the initial defense against bacterial pathogens. The crosstalk between host cells infected with intracellular pathogens and NK cells has been studied intensively, but not much attention has been given to characterize the role of NK cells in the response to extracellular bacterial pathogens such as yersiniae. In this study we used antibody-mediated NK cell depletion to address the importance of this immune cell type in controlling a Y. pseudotuberculosis infection. Analysis of the bacterial counts was used to follow the infection and flow cytometry was performed to characterize the composition and dynamic of immune cells. Depletion of NK cells led to higher bacterial loads within the mesenteric lymph nodes. We further show that in particular CD11b⁺ CD27⁺ NK cells which express higher levels of the activation marker CD69 increase within the mesenteric lymph nodes during a Y. pseudotuberculosis infection. Moreover, in response to the activation NK cells secrete higher levels of IFNy, which in turn triggers the production of the proinflammatory cytokine TNFα. These results suggest, that NK cells aid in the clearance of Y. pseudotuberculosis infections mainly by triggering the expression of proinflammatory cytokines manipulating the host immune response.

In vitro model to study the biomaterial-dependent reaction of macrophages in an inflammatory environment

Background

Macrophages play an important role in the reaction to biomaterials, which sometimes have to be used in a surgical field at risk of contamination. The macrophage phenotype in reaction to biomaterials in an inflammatory environment was evaluated in both an in vivo and in vitro setting.

Methods

In the in vivo setting, polypropylene (PP) biomaterial was implanted for 28 days in the contaminated abdominal wall of rats, and upon removal analysed by routine histology as well as immunohistochemistry for CD68 (marker for macrophages), inducible nitric oxide synthase (iNOS – a marker for proinflammatory M1 macrophages) and CD206 (marker for anti-inflammatory M2 macrophages). For the in vitro model, human peripheral blood monocytes were cultured for 3 days on biomaterials made from PP, collagen (COL), polyethylene terephthalate (PET) and PET coated with collagen (PET+COL). These experiments were performed both with and without lipopolysaccharide and interferon γ stimulation. Secretion of both M1- and M2-related proteins was measured, and a relative M1/M2 index was calculated.

Results

In vivo, iNOS- and CD206-positive cells were found around the fibres of the implanted PP biomaterial. In vitro, macrophages on both PP and COL biomaterial had a relatively low M1/M2 index. Macrophages on the PET biomaterial had a high M1/M2 index, with the highest increase of M1 cytokines in an inflammatory environment. Macrophages on the PET+COL biomaterial also had a high M1/M2 index.

Conclusion

Macrophages in an inflammatory environment in vitro still react in a biomaterial-dependent manner. This model can help to select biomaterials that are tolerated best in a surgical environment at risk of contamination.

Surgical relevance

Biomaterials in an environment at risk of contamination are often not tolerated owing to a high risk of postoperative infection, which may ultimately lead to removal of the biomaterial.

An in vitro model with primary human macrophages was used to provide insight into the acute reaction of macrophages to a biomaterial in an inflammatory environment simulated with lipopolysaccharide and interferon γ. The reaction of macrophages in such an inflammatory environment was still biomaterial-dependent.

This in vitro model can be used to study the reaction of macrophages to different biomaterials in an inflammatory environment in more detail, and thereby help to select biomaterials that are tolerated best in a surgical environment at risk of contamination.

Impaired NK cell antiviral cytokine response against influenza virus in small-for-gestational-age neonates

The neonates, particularly small-for-gestational-age (SGA) ones, are susceptible to various microbial infections. Natural killer (NK) cells are critical components of host innate immunity system and the main source of the inflammatory cytokines, which provide critical protection during the early phase of viral infections before the development of an appropriate adaptive immune response. However, little is known about the antiviral effects of NK cells in neonates especially the SGA population. Herein, a prospective descriptive study was performed to determine the differences of NK cell immunity among adults, appropriate-for gestational-age (AGA) and SGA neonates. Adults have much higher NK cell number in peripheral blood than that in cord blood from neonates. In response to influenza virus stimulation, neonatal NK cells, especially SGA baby cells, expressed significantly lower antiviral cytokines including perforin, interferon (IFN)-γ and tumor-necrosis factor (TNF)-α responses than adult NK cells. In addition, the antiviral cytokine responses of NK cells were positively correlated with neonatal birth weight. Our data suggested that the depressed antiviral activity and less frequency of NK cells are likely to be responsible for the high susceptibility to microbial infection in neonates, at least in part. Improving the function of innate immunity may provide a new way to defend virus infection.

IL-18 provided in dying bacterial-infected macrophages induces IFN-γ production in functional T-cell hybridoma B6HO3 through cell conjugates

We have previously reported that the co-culture of functional T-cell hybridoma B6HO3 with dying J774 macrophage cells infected with Listeria monocytogenes (LM) results in the production of IFN-γ by B6HO3 cells. Here, we explore the mechanism underlying this phenomenon. We found that IFN-γ production was dependent on IL-18, but that the dying LM-infected macrophages produced no more than 100 pg/ml of IL-18, much less than the amount of IL-18 required for stimulating B6HO3 cells to produce IFN-γ. Furthermore, IL-18 binding protein added to the co-culture was unable to easily gain access to IL-18 for neutralisation. B6HO3 cells formed cell conjugates with J774 macrophages, and IFN-γ-producing B6HO3 cells were spatially and temporally associated with LM-infected macrophage cell death that exhibited neither pyroptosis nor pyronecrosis. These results suggest that the IL-18 produced by dying LM-infected macrophages is released to the interface of the cell conjugates, thereby inducing B6HO3 cells to produce IFN-γ. Based on the present and also previous findings, we propose that IL-18 released from macrophages because of cell death caused by bacteria may be the primary cytokine that triggers the innate IFN-γ production that is required for activating the bactericidal functions of macrophages at early stages of bacterial infection.

Solute carrier 11A1 is expressed by innate lymphocytes and augments their activation

Solute carrier 11A1 (SLC11A1) is a divalent ion transporter formerly known as the natural resistance-associated macrophage protein (NRAMP1) and the Bcg/Lsh/Ity locus. SLC11A1 was thought to be exclusively expressed in monocyte/macrophages and to have roles in phagosome maturation and cell activation. We characterized the expression of SLC11A1 in the majority of human and bovine γδ T cells and NK cells and in human CD3(+)CD45RO(+) T cells. Consistent with a role for iron-dependent inhibition of protein tyrosine phosphatases, SLC11A1(+) lymphocytes were more prone to activation and retained tyrosine phosphorylation. Transfection of SLC11A1 into a human γδ T cell-like line rendered the cells more prone to activation. Nonadherent splenocytes from wild-type mice expressed significantly greater IFN-γ compared with cells from Sv/129 (SLC11A1(-/-)) mice. Our data suggest that SLC11A1 has a heretofore unknown role in activation of a large subset of innate lymphocytes that are critical sources of IFN-γ. SLC11A1(+) animals have enhanced innate IFN-γ expression in response to Salmonella infection compared with SLC11A1(-) mice, which include commonly used inbred laboratory mice. Expression of SLC11A1 in innate lymphocytes and its role in augmenting their activation may account for inconsistencies in studies of innate lymphocytes in different animal models.

Gamma-delta T-cell responses during subcutaneous Mycobacterium avium subspecies paratuberculosis challenge in sensitized or naive calves using matrix biopolymers

We have developed a model to explore the early immune response against Mycobacterium avium subspecies paratuberculosis (Map) infection in the bovine calf using subcutaneously placed liquid gel matrix biopolymer (matrigel) containing live Map. Matrigel rapidly polymerizes in vivo, retains recruited cellular infiltrates and soluble immune mediators, and can be rapidly removed 48 hours later and depolymerized for analysis. In this study, we examined early host immune events at matrigel/Map sites; recruited cells were evaluated by histopathology and flow cytometry, and cytokines were measured by flow cytometry, enzyme-linked immunosorbent assay, and Luminex bead immunoassay. Our results demonstrate earlier recruitment of gamma-delta (γδ) T cells to matrigel/Map challenge sites compared to CD4+ T cells. We also show that significantly more γδ T cells were recruited to matrigel/Map sites postinfection day 7 compared to postinfection day 30 and that these cells produced significant amounts of the cytokine interferon gamma. We also provide evidence that peripheral blood-derived γδ T-cell subsets in cattle differentially generate interferon gamma, suggesting distinct roles for these cells. These data provide unique insight into initial antimycobacterial host cellular immune responses following Map infection in calves.

Innate IFN-γ-producing cells in the spleen of mice early after Listeria monocytogenes infection: importance of microenvironment of the cells involved in the production of innate IFN-γ

Production of innate interferon-γ (IFN-γ) is a crucial step in immunological defense against bacteria. However, there is little information regarding cellular mechanisms underlying IFN-γ production in vivo early after bacterial infection. Here we analyze innate IFN-γ production in the spleen of mice early after Listeria monocytogenes (LM) infection ex vivo by flow-cytometry and in situ by immunohistochemistry, and compare them with the IFN-γ-producing cells reported previously in our in vitro coculture system in which cell-cell interaction between lymphocytes and dying bacterial-infected macrophages is required for the production of IFN-γ. In the spleen at 20 h after LM infection, natural killer (NK) cells, a subset of αβ T cells, and subsets of NKT and γδ T cells produced IFN-γ with features similar to the IFN-γ-producing cells in our in vitro coculture system. Immunohistochemistry revealed that LM bacteria were first phagocytosed mainly by ER-TR9⁺ marginal zone macrophages (MZMs), then forming infectious foci in close vicinity of the marginal zone (MZ) at 20-h postinfection. At this time point, the IFN-γ-producing cells were accumulating at the same site of infectious foci, around which ER-TR9⁺ MZMs were clustered but most of bacteria were no longer associated with ER-TR9⁺ MZMs. These results indicate that innate IFN-γ production by innate lymphocytes takes place at infectious foci formed in close vicinity of the MZ, and they also suggest an important role for the microenvironment of the cells accumulated at infectious foci in inducing the production of innate IFN-γ.

Comparative gamma delta T cell immunology: a focus on mycobacterial disease in cattle

A theme among many pathogenic mycobacterial species affecting both humans and animals is a prolonged asymptomatic or latent period that can last years to decades. The mechanisms that favor progression to active disease are not well understood. Pathogen containment is often associated with an effective cell-mediated or T-helper 1 immune profile. With certain pathogenic mycobacteria, such as Mycobacterium avium subspecies paratuberculosis, a shift to active clinical disease is associated with loss of T-helper 1 immunity and development of an ineffective humoral or T-helper 2 immune response. Recently γδ T cells have been shown to play a role early in mycobacterial infections and have been hypothesized to influence disease outcome. The purpose of this paper is to compare recent advancements in our understanding of γδ T cells in humans, cattle, and mice and to discuss roles of γδ T cells in host response to mycobacterial infection.

Delineation of the innate and adaptive T-cell immune outcome in the human host in response to Campylobacter jejuni infection

BACKGROUND

Campylobacter jejuni is the most prevalent cause of bacterial gastroenteritis worldwide. Despite the significant health burden this infection presents, molecular understanding of C. jejuni-mediated disease pathogenesis remains poorly defined. Here, we report the characterisation of the early, innate immune response to C. jejuni using an ex-vivo human gut model of infection. Secondly, impact of bacterial-driven dendritic cell activation on T-cell mediated immunity was also sought.

METHODOLOGY

Healthy, control paediatric terminal ileum or colonic biopsy tissue was infected with C. jejuni for 8-12 hours. Bacterial colonisation was followed by confocal microscopy and mucosal innate immune responses measured by ELISA. Marked induction of IFNγ with modest increase in IL-22 and IL-17A was noted. Increased mucosal IL-12, IL-23, IL-1β and IL-6 were indicative of a cytokine milieu that may modulate subsequent T-cell mediated immunity. C. jejuni-driven human monocyte-derived dendritic cell activation was followed by analyses of T cell immune responses utilising flow cytometry and ELISA. Significant increase in Th-17, Th-1 and Th-17/Th-1 double-positive cells and corresponding cytokines was observed. The ability of IFNγ, IL-22 and IL-17 cytokines to exert host defence via modulation of C. jejuni adhesion and invasion to intestinal epithelia was measured by standard gentamicin protection assay.

CONCLUSIONS

Both innate and adaptive T cell-immunity to C. jejuni infection led to the release of IFNγ, IL-22 and IL-17A; suggesting a critical role for this cytokine triad in establishing host anti-microbial immunity during the acute and effectors phase of infection. In addition, to their known anti-microbial functions; IL-17A and IL-17F reduced the number of intracellular C. jejuni in intestinal epithelia, highlighting a novel aspect of how IL-17 family members may contribute to protective immunity against C. jejuni.