Dendritic cells: the commanders-in-chief of mucosal immune defenses

Cell-Type-Specific ROS-AKT/mTOR-Autophagy Interplay-Should It Be Addressed in Periimplantitis?

Periimplantitis represents an inflammatory disease of the soft and hard tissues surrounding the osseointegrated dental implant, triggering progressive damage to the alveolar bone. Cumulative data have revealed that periimplantitis plays a crucial part in implant failure. Due to the strategic roles of autophagy and its upstream coordinator, the AKT/mTOR pathway, in inflammatory responses, the crosstalk between them in the context of periimplantitis should become a key research target, as it opens up an area of interesting data with clinical significance. Therefore, in this article, we aimed to briefly review the existing data concerning the complex roles played by ROS in the interplay between the AKT/mTOR signaling pathway and autophagy in periimplantitis, in each of the main cell types involved in periimplantitis pathogenesis and evolution. Knowing how to modulate specifically the autophagic machinery in each of the cellular types involved in the healing and osseointegration steps post implant surgery can help the clinician to make the most appropriate post-surgery decisions. These decisions might be crucial in order to prevent the occurrence of periimplantitis and ensure the proper conditions for effective osseointegration, depending on patients' clinical particularities.

A guide to oral vaccination: Highlighting electrospraying as a promising manufacturing technique toward a successful oral vaccine development

Most vaccines approved by regulatory bodies are administered via intramuscular or subcutaneous injections and have shortcomings, such as the risk of needle-associated blood infections, pain and swelling at the injection site. Orally administered vaccines are of interest, as they elicit both systemic and mucosal immunities, in which mucosal immunity would neutralize the mucosa invading pathogen before the onset of an infection. Hence, oral vaccination can eliminate the injection associated adverse effects and enhance the person's compliance. Conventional approaches to manufacturing oral vaccines, such as coacervation, spray drying, and membrane emulsification, tend to alter the structural proteins in vaccines that result from high temperature, organic and toxic solvents during production. Electrohydrodynamic processes, specifically electrospraying, could solve these challenges, as it also modulates antigen release and has a high loading efficiency. This review will highlight the mucosal immunity and biological basis of the gastrointestinal immune system, different oral vaccine delivery approaches, and the application of electrospraying in vaccines development.

From initial segment to cauda: a regional characterization of mouse epididymal CD11c+ mononuclear phagocytes based on immune phenotype and function

Successful sperm maturation and storage rely on a unique immunological balance that protects the male reproductive organs from invading pathogens and spermatozoa from a destructive autoimmune response. We previously characterized one subset of mononuclear phagocytes (MPs) in the murine epididymis, CX3CR1⁺ cells, emphasizing their different functional properties. This population partially overlaps with another subset of understudied heterogeneous MPs, the CD11c⁺ cells. In the present study, we analyzed the CD11c⁺ MPs for their immune phenotype, morphology, and antigen capturing and presenting abilities. Epididymides from CD11c-EYFP mice, which express enhanced yellow fluorescent protein (EYFP) in CD11c⁺ MPs, were divided into initial segment (IS), caput/corpus, and cauda regions. Flow cytometry analysis showed that CD11c⁺ MPs with a macrophage phenotype (CD64⁺ and F4/80⁺) were the most abundant in the IS, whereas those with a dendritic cell signature [CD64^- major histocompatibility complex class II (MHCII)⁺] were more frequent in the cauda. Immunofluorescence revealed morphological and phenotypic differences between CD11c⁺ MPs in the regions examined. To assess the ability of CD11c⁺ cells to take up antigens, CD11c-EYFP mice were injected intravenously with ovalbumin. In the IS, MPs expressing macrophage markers were most active in taking up the antigens. A functional antigen-presenting coculture study was performed, whereby CD4⁺ T cells were activated after ovalbumin presentation by CD11c⁺ epididymal MPs. The results demonstrated that CD11c⁺ MPs in all regions were capable of capturing and presenting antigens. Together, this study defines a marked regional variation in epididymal antigen-presenting cells that could help us understand fertility and contraception but also has larger implications in inflammation and disease pathology.

Disruption of Immune Homeostasis in Human Dendritic Cells via Regulation of Autophagy and Apoptosis by Porphyromonas gingivalis

As fundamental processes of immune homeostasis, autophagy, and apoptosis must be maintained to mitigate risk of chronic inflammation and autoimmune diseases. Periodontitis is a chronic inflammatory disease characterized by oral microbial dysbiosis, and dysregulation of dendritic cell (DC) and T cell responses. The aim of this study was to elucidate the underlying mechanisms by which the oral microbe Porphyromonas gingivalis (P. gingivalis) manipulates dendritic cell signaling to perturb both autophagy and apoptosis. Using a combination of Western blotting, flow cytometry, qRT-PCR and immunofluorescence analysis, we show a pivotal role for the minor (Mfa1) fimbriae of P. gingivalis in nuclear/cytoplasmic shuttling of Akt and FOXO1 in human monocyte-derived DCs. Mfa1-induced Akt nuclear localization and activation ultimately induced mTOR. Activation of the Akt/mTOR axis downregulated intracellular LC3II, also known as Atg8, required for autophagosome formation and maturation. Use of allosteric panAkt inhibitor MK2206 and mTOR inhibitor rapamycin confirmed the role of Akt/mTOR signaling in autophagy inhibition by P. gingivalis in DCs. Interestingly, this pathway was also linked to induction of the anti-apoptotic protein Bcl2, decreased caspase-3 cleavage and decreased expression of pro-apoptotic proteins Bax and Bim, thus promoting longevity of host DCs. Addition of ABT-199 peptide to disrupt the interaction of antiapoptotic Bcl2 and its proapoptotic partners BAK/BAX restored apoptotic death to P. gingivalis-infected DC cells. In summary, we have identified the underlying mechanism by which P. gingivalis promotes its own survival and that of its host DCs.

Adoptive transfer of dendritic cells expressing CD11c reduces the immunological response associated with experimental colitis in BALB/c mice

INTRODUCTION

In addition to conventional therapies, several new strategies have been proposed for modulating autoimmune diseases, including the adoptive transfer of immunological cells. In this context, dendritic cells (DCs) appear to be one of the most promising treatments for autoimmune disorders. The present study aimed to evaluate the effects of adoptive transfer of DCs obtained from both naïve and ovalbumin (OVA)-tolerant mice on the severity of TNBS induced colitis and analyze the eventual protective mechanisms.

METHODS AND RESULTS

To induce oral tolerance, BALB/c mice were fed 4mg/mL OVA solution for seven consecutive days. Spleen DCs were isolated from tolerant (tDC) and naïve (nDC) mice, and then adoptively transferred to syngeneic mice. Three days later, colitis was induced in DC treated mice by intrarectal instillation of 100μg2,4,6-trinitrobenzenesulfonic acid (TNBS) dissolved in 50% ethanol. Control subjects received only intrarectal instillation of either TNBS solution or a vehicle. Five days later, mice from all groups were euthanized and examined for physiological and immunological parameters. Regarding the phenotype, we observed that the frequencies of CD11+ MHC II+ and CD11+ MHCII+ CD86+ cells were significantly lower in DCs isolated from tolerant mice than in those from naive mice. However, pretreatment with both types of DCs was able to significantly reduce clinical signs of colitis such as diarrhea, rectal prolapse, bleeding, and cachexia, although only treatment with tDCs was able to prevent weight loss from instillation of TNBS. In vitro proliferation of spleen cells from mice treated with either type of DCs was significantly lower than that observed in splenic cell cultures of naïve mice. Although no significant difference was observed in the frequencies of Treg cells in the experimental groups, the frequency of Th17+CD4+cellsand the secretion of IL-17 were more reduced in the cultures of spleen cells from mice treated with either type of DCs. The levels of IL-9 and IFN-γ were lower in supernatants of cells from mice treated with nDCs.

CONCLUSION

The results allow us to conclude that the adoptive transfer of cells expressing CD11c is able to reduce the clinical and immunological signs of drug-induced colitis. Adoptive transfer of CD11c+DC isolated from both naive and tolerant mice altered the proliferative and T cell responses. To the best of our knowledge, there is no previously published data showing the protective effects of DCs from naïve or tolerant mice in the treatment of colitis.

TLR2 and TLR4 as Potential Biomarkers of Environmental Particulate Matter Exposed Human Myeloid Dendritic Cells

In many subjects who are genetically susceptible to asthma, exposure to environmental stimuli may exacerbate their condition. However, it is unknown how the expression and function of a family of pattern-recognition receptors called toll-like receptors (TLR) are affected by exposure to particulate pollution. TLRs serve a critical function in alerting the immune system of tissue damage or infection—the so-called “danger signals”. We are interested in the role that TLRs play in directing appropriate responses by innate immunity, particularly dendritic cells (DC), after exposing them to particulate pollution. Dendritic cells serve a pivotal role in directing host immunity. Thus, we hypothesized that alterations in TLR expression could be further explored as potential biomarkers of effect related to DC exposure to particulate pollution. We show some preliminary data that indicates that inhaled particulate pollution acts directly on DC by down-regulating TLR expression and altering the activation state of DC. While further studies are warranted, we suggest that alterations in TLR2 and TLR4 expression should be explored as potential biomarkers of DC exposure to environmental particulate pollution.

Programming and memory dynamics of innate leukocytes during tissue homeostasis and inflammation

The field of innate immunity is witnessing a paradigm shift regarding "memory" and "programming" dynamics. Past studies of innate leukocytes characterized them as first responders to danger signals with no memory. However, recent findings suggest that innate leukocytes, such as monocytes and neutrophils, are capable of "memorizing" not only the chemical nature but also the history and dosages of external stimulants. As a consequence, innate leukocytes can be dynamically programmed or reprogrammed into complex inflammatory memory states. Key examples of innate leukocyte memory dynamics include the development of primed and tolerant monocytes when "programmed" with a variety of inflammatory stimulants at varying signal strengths. The development of innate leukocyte memory may have far-reaching translational implications, as programmed innate leukocytes may affect the pathogenesis of both acute and chronic inflammatory diseases. This review intends to critically discuss some of the recent studies that address this emerging concept and its implication in the pathogenesis of inflammatory diseases.

Exploring the role of mononuclear phagocytes in the epididymis

The onslaught of foreign antigens carried by spermatozoa into the epididymis, an organ that has not demonstrated immune privilege, a decade or more after the establishment of central immune tolerance presents a unique biological challenge. Historically, the physical confinement of spermatozoa to the epididymal tubule enforced by a tightly interwoven wall of epithelial cells was considered sufficient enough to prevent cross talk between gametes and the immune system and, ultimately, autoimmune destruction. The discovery of an intricate arrangement of mononuclear phagocytes (MPs) comprising dendritic cells and macrophages in the murine epididymis suggests that we may have underestimated the existence of a sophisticated mucosal immune system in the posttesticular environment. This review consolidates our current knowledge of the physiology of MPs in the steady state epididymis and speculates on possible interactions between auto-antigenic spermatozoa, pathogens and the immune system by drawing on what is known about the immune system in the intestinal mucosa. Ultimately, further investigation will provide valuable information regarding the origins of pathologies arising as a result of autoimmune or inflammatory responses in the epididymis, including epididymitis and infertility.

Macrophages and dendritic cells in the post-testicular environment

Macrophages (MΦ) and dendritic cells (DCs) are heterogeneous families of functionally and developmentally related immune cells that play crucial roles in tissue homeostasis and the regulation of immune responses. During the past 5 years, immunologists have generated a considerable amount of data that challenge dogmas about the ontogeny and functions of these highly versatile cells. The male excurrent duct system plays a critical role in the establishment of fertility by allowing sperm maturation, transport and storage. In addition, it is challenged by pathogens and must establish a protective and tolerogenic environment for a continuous flow of autoantigenic spermatozoa. The post-testicular environment and, in particular, the epididymis contain an intricate network of DCs and MΦ; however, the immunophysiology of this intriguing and highly specialized mucosal system is poorly understood. This review summarizes the current trends in mouse MΦ and DC biology and speculates about their roles in the steady-state epididymis. Unraveling immune cell functions in the male reproductive tract is an essential prerequisite for the design of innovative strategies aimed at controlling male fertility and treating infertility.

Effect of a protein-free diet in the development of food allergy and oral tolerance in BALB/c mice

The aim of the present study was to investigate the effect of a protein-free diet in the induction of food allergy and oral tolerance in BALB/c mice. The experimental model used was mice that were fed, since weaning up to adulthood, a balanced diet in which all dietary proteins were replaced by amino acid diet (Aa). The absence of dietary proteins did not prevent the development of food allergy to ovalbumin (OVA) in these mice. However, Aa-fed mice produced lower levels of IgE, secretory IgA and cytokines. In addition, when compared with mice from control group, Aa-fed mice had a milder aversive reaction to the allergen measured by consumption of OVA-containing solution and weight loss during food allergy development. In addition, mice that did not have dietary proteins in their diets were less susceptible to induction of oral tolerance. One single oral administration was not enough to suppress specific serum Ig and IgG1 levels in the Aa-fed group, although it was efficient to induce suppression in the control group. The present results indicate that the stimulation by dietary proteins alters both inflammatory reactivity and regulatory immune reactivity in mice probably due to their effect in the maturation of the immune system.

Of worms, mice and man: an overview of experimental and clinical helminth-based therapy for inflammatory bowel disease

The incidence of inflammatory and autoimmune disorders is highest in well-developed countries which is directly related to their higher hygienic standards: it is suggested that the lack of exposure to helminths contributes to the susceptibility for immune-related diseases. Epidemiological, experimental and clinical data support the idea that helminths provide protection against immune-mediated diseases such as inflammatory bowel disease (IBD). The most likely mechanism for the suppression of immune responses by helminths is the release of helminth-derived immunomodulatory molecules. This article reviews the experimental and clinical studies investigating the therapeutic potential of helminth-based therapy in IBD and also focuses on the current knowledge of its immunomodulatory mechanisms of action highlighting innate as well as adaptive immune mechanisms. Identifying the mechanisms by which these helminths and helminth-derived molecules modulate the immune system will help in creating novel drugs for the treatment of IBD and other disorders that result from an overactive immune response.

Epithelial basal cells are distinct from dendritic cells and macrophages in the mouse epididymis

The epithelium that lines the epididymal duct establishes the optimal milieu in which spermatozoa mature, acquire motility, and are stored. This finely tuned environment also protects antigenic sperm against pathogens and autoimmunity, which are potential causes of transient or permanent infertility. The epididymal epithelium is pseudostratified and contains basal cells (BCs) that are located beneath other epithelial cells. Previous studies showed that in the mouse epididymis, BCs possess macrophage-like characteristics. However, we previously identified a dense population of cells belonging to the mononuclear phagocyte (MP) system (comprised of macrophages and dendritic cells) in the basal compartment of the mouse epididymis and showed that a subset of MPs express the macrophage marker F4/80. In the present study, we evaluate the distribution of BCs and MPs in the epididymis of transgenic CD11c-EYFP mice, in which EYFP is expressed exclusively in MPs, using antibodies against the BC marker keratin 5 (KRT5) and the macrophage marker F4/80. Immunofluorescence labeling for laminin, a basement membrane marker, showed that BCs and most MPs are located in the basal region of the epithelium. Confocal microscopy showed that in the initial segment, both BCs and MPs project intraepithelial extensions and establish a very intricate network. Flow cytometry experiments demonstrated that epididymal MPs and BCs are phenotypically distinct. BCs do not express F4/80, and MPs do not express KRT5. Therefore, despite their proximity and some morphological similarities with peritubular macrophages and dendritic cells, BCs do not belong to the MP system.

Interactions between the intestinal microbiota and innate lymphoid cells

The mammalian intestine must manage to contain 100 trillion intestinal bacteria without inducing inappropriate immune responses to these microorganisms. The effects of the immune system on intestinal microorganisms are numerous and well-characterized, and recent research has determined that the microbiota influences the intestinal immune system as well. In this review, we first discuss the intestinal immune system and its role in containing and maintaining tolerance to commensal organisms. We next introduce a category of immune cells, the innate lymphoid cells, and describe their classification and function in intestinal immunology. Finally, we discuss the effects of the intestinal microbiota on innate lymphoid cells.

Lost therapeutic potential of monocyte-derived dendritic cells through lost tissue homing: stable restoration of gut specificity with retinoic acid

Human monocyte-derived dendritic cells (DC) (MoDC) are utilized for immunotherapy. However, in-vitro immunological effects are often not mirrored in vivo. We studied the tissue-homing potential of MoDC. Circulating monocytes and DC expressed different tissue-homing markers and, during in-vitro development of MoDC, homing marker expression was lost resulting in a 'homeless' phenotype. Retinoic acid (RA) induced gut-homing markers (β7 and CCR9) and a regulatory phenotype and function [decreased human leucocyte antigen D-related (HLA-DR) and increased ILT3 and fluorescein isothiocyanate (FITC-dextran uptake) in MoDC]. RA-MoDC were less stimulatory and primed conditioned T cells with a gut-homing profile (β7(+)CLA(-)). Unlike the normal intestinal microenvironment, that from inflamed colon of ulcerative colitis (UC) patients did not induce regulatory properties in MoDC. However, RA-MoDC maintained their regulatory gut-specific properties even in the presence of UC microenvironment. Therefore, MoDC may be ineffectual for immunotherapy because they lack tissue-homing and tissue-imprinting specificity. However, MoDC rehabilitation with gut-homing potential by RA could be useful in promoting immunotherapy in pathologies such as UC.

Cockroach allergen Bla g 7 promotes TIM4 expression in dendritic cells leading to Th2 polarization

As one of the most common sources of indoor aeroallergens worldwide, cockroach is important in causing rhinitis and asthma while the mechanisms underlying remain obscure. Since T helper (Th) type 2 polarization plays an important role in the pathogenesis of allergic diseases, we investigated the effect of Bla g 7, a pan-allergen from Blattella germanica (B. germanica), on Th polarization which is controlled by monocyte-derived dendritic cells (DCs). Challenged by recombinant Bla g 7 (rBla g 7), immature DCs obtained from human exhibited upregulated levels of TIM4, CD80, and CD86 and increased IL-13 secretion. Cocultured with CD4+ T cells, challenged DCs increased the ratio of IL-4+ versus IFN-γ+ of CD4+ T cells, suggesting a balance shift from Th1 to Th2. Moreover, antibodies against TIM4, CD80, and CD86 reversed the enhancement of IL-4+/IFN-γ+ ratio and alleviated the IL-13 release induced by rBla g 7, indicating that the Th2 polarization provoked by rBla g 7 challenged DCs is via TIM4-, CD80-, and CD86-dependent mechanisms. In conclusion, the present findings implied a crucial role of Bla g 7 in the development of cockroach allergy and highlighted an involvement of DCs-induced Th2 polarization in cockroach allergy.

IL-6 promotes immune responses in human ulcerative colitis and induces a skin-homing phenotype in the dendritic cells and Tcells they stimulate

Dendritic cells (DCs) control the type and location of immune responses. Ulcerative colitis (UC) is considered a Th2 disease mediated by IL-13 where up to one third of patients can develop extraintestinal manifestations. Colonic biopsies from inflamed and noninflamed areas of UC patients were cultured in vitro and their supernatants were used to condition human blood enriched DCs from healthy controls. Levels of IL-13 in the culture supernatants were below the detection limit in most cases and the cytokine profile suggested a mixed profile rather than a Th2 cytokine profile. IL-6 was the predominant cytokine found in inflamed areas from UC patients and its concentration correlated with the Mayo endoscopic score for severity of disease. DCs conditioned with noninflamed culture supernatants acquired a regulatory phenotype with decreased stimulatory capacity. However, DCs conditioned with inflamed culture supernatants acquired a proinflammatory phenotype with increased expression of the skin-homing chemokine CCR8. These DCs did not have decreased T-cell stimulatory capacity and primed T cells with the skin-homing CLA molecule in an IL-6-dependent mechanism. Our results highlight the role of IL-6 in UC and question the concept of UC as a Th2 disease and the relevance of IL-13 in its etiology.

Role of natural killer and dendritic cell crosstalk in immunomodulation by commensal bacteria probiotics

A cooperative dialogue between natural killer (NK) cells and dendritic cells (DCs) has been elucidated in the last years. They help each other to acquire their complete functions, both in the periphery and in the secondary lymphoid organs. Thus, NK cells' activation by dendritic cells allows the killing of transformed or infected cells in the periphery but may also be important for the generation of adaptive immunity. Indeed, it has been shown that NK cells may play a key role in polarizing a Th1 response upon interaction with DCs exposed to microbial products. This regulatory role of DC/NK cross-talk is of particular importance at mucosal surfaces such as the intestine, where the immune system exists in intimate association with commensal bacteria such as lactic acid bacteria (LAB). We here review NK/DC interactions in the presence of gut-derived commensal bacteria and their role in bacterial strain-dependent immunomodulatory effects. We particularly aim to highlight the ability of distinct species of commensal bacterial probiotics to differently affect the outcome of DC/NK cross-talk and consequently to differently influence the polarization of the adaptive immune response.

A dense network of dendritic cells populates the murine epididymis

One of the most intriguing aspects of male reproductive physiology is the ability to generate spermatogenic cells - which are 'foreign' to the host - without triggering immune activation. After leaving the testis, spermatozoa enter the epididymis where they mature and are stored. In this study, we report a previously unrecognized dense network of dendritic cells (DCs) located at the base of the epididymal epithelium. This network was detected in transgenic mice expressing CD11c-EYFP and CX3CR1-GFP reporters. Epididymal DCs (eDCs) establish intimate interactions with the epithelium and project long dendrites between epithelial cells toward the lumen. We show that isolated eDCs express numerous leukocyte markers described previously in other organs that are in contact with the external environment, and present and cross-present ovalbumin to T cells in vitro. eDCs are, therefore, strategically positioned to regulate the complex interplay between immune tolerance and activation, a balance that is fundamental to male fertility.

Targeting the innate immune system in pediatric inflammatory bowel disease

The pathogenesis of inflammatory bowel disease (IBD) is complex and involves both innate and adaptive immune responses. This article addresses, in a selective and speculative fashion, the topic of how the various components of the intestinal innate immune system can be manipulated for the purpose of developing new therapeutic approaches. These various components include: agents that stimulate mucosal innate immune responses, such as food components and the gut microbiota; cells that directly respond to these stimuli, including epithelial cells, macrophages and dendritic cells; and molecules that mediate innate immune responses, such as Toll-like receptors and protein kinases. Downregulation of excessive innate immune responses makes therapeutic sense in both pediatric and adult IBD. However, because IBD is complex and characteristically chronic, major alterations of adaptive immunity are also involved in the mediation of inflammation. Thus, novel and truly effective approaches to treat IBD will undoubtedly require intervening in the innate as well as the adaptive branches of the mucosal immunity.

Tumor necrosis factor-α-secreting CD16+ antigen presenting cells are effectively removed by granulocytapheresis in ulcerative colitis patients

BACKGROUND AND AIM

In human blood, two main subsets of antigen-presenting-cells (APCs) have been described: plasmocytoid dendritic cells (pDC) and myeloid dendritic cells (mDC) which are further subdivided in CD11c-mDC and CD16-mDC DC. In ulcerative colitis patients (UC) peripheral blood APCs express significant levels of the activation and lack immature-tolerogeneic APCs. Adacolumn selective granulocytapheresis (GCAP) has been associated with clinical efficacy in patients with UC. In the present study we sought the effect of sequential GCAP procedures in peripheral blood APCs in patients with UC and the effect on soluble cytokines.

METHODS

We used multiparametric flow cytometry to quantify peripheral blood APCs and serum cytokines in 210 samples obtained from seven patients with steroid-dependent or steroid resistant UC undergoing GCAP treatment. Samples were drawn before, after 30 and 60 min of each session.

RESULTS

Each GCAP session resulted in a dramatic tenfold reduction of peripheral blood CD16-mDC (P < 0.01), pDC decreased twofold (P = 0.05) but CD11c-mDC remained unchanged. This depletion was reached after 30 min and maintained at 60 min. The depletion of CD16-mDC and monocytes was associated with a reduction of serum tumor necrosis factor levels and a raise in interleukin-10 levels, although no statistical difference was reached.

CONCLUSION

The effect of GCAP in peripheral blood APC consisted mainly on a significant depletion of tumor necrosis factor-α secreting CD16-mDC. This finding could suggest a potential mechanism of GCAP beneficial effect that must be confirmed in larger series.

TL and CD8αα: Enigmatic partners in mucosal immunity

The intestinal mucosa represents a large surface area that is in contact with an immense antigenic load. The immune system associated with the intestinal mucosa needs to distinguish between innocuous food antigens, commensal microorganisms, and pathogenic microorganisms, without triggering an exaggerated immune response that may lead to excessive inflammation and/or development of inflammatory bowel disease. The thymus leukemia (TL) antigen and CD8αα are interacting surface molecules that are expressed at the frontline of the mucosal immune system: TL is expressed in intestinal epithelial cells (IEC) whereas CD8αα is expressed in lymphocytes, known as intraepithelial lymphocytes, that reside in between the IEC. In this review we discuss the significance of the interaction between TL and CD8αα in mucosal immunity during health and disease.

Induction of regulatory T cells decreases adipose inflammation and alleviates insulin resistance in ob/ob mice

Leptin-deficient ob/ob mice are overweight, develop insulin resistance, and serve as a model for type 2 diabetes (T2D). Studies suggest that inflammatory pathways are linked to the development of insulin resistance and T2D both in animals and humans. We asked whether the induction of regulatory T cells (Tregs) could alleviate the pathological and metabolic abnormalities in ob/ob mice. We induced TGF-beta-dependent CD4(+) latency-associated peptide (LAP)-positive Tregs by oral administration of anti-CD3 antibody plus beta-glucosylceramide. We found a decrease in pancreatic islet cell hyperplasia, fat accumulation in the liver, and inflammation in adipose tissue, accompanied by lower blood glucose and liver enzymes. In addition, treated animals had decreased CD11b(+)F4/80(+) macrophages and TNF-alpha in adipose tissue. Adoptive transfer of orally induced CD4(+)LAP(+) Tregs ameliorated metabolic and cytokine abnormalities. Our results demonstrate the importance of inflammation in T2D and identify a unique immunological approach for treatment of T2D by the induction of Tregs.

Human intestinal lamina propria CD1c+ dendritic cells display an activated phenotype at steady state and produce IL-23 in response to TLR7/8 stimulation

Intestinal dendritic cells (DCs) play key roles in mediating tolerance to commensal flora and inflammatory responses against mucosal pathogens. The mechanisms by which intestinal "conditioning" influences human DC responses to microbial stimuli remain poorly understood. Infections with viruses, such as HIV-1, that target mucosal tissue result in intestinal epithelial barrier breakdown and increased translocation of commensal bacteria into the lamina propria (LP). It is unclear whether innate LP DC responses to concurrent viral and bacterial stimuli influence mucosal HIV-1 pathogenesis. In this study, direct ex vivo phenotype and in vitro constitutive cytokine production of CD1c+ DCs in human intestinal LP were compared with those in peripheral blood (PB). To evaluate innate responses to viral and bacterial stimuli, intracellular cytokine production by LP and PB DCs following stimulation with ligands for TLRs 2, 4, 5, and 7/8 was evaluated. At steady state, LP CD1c+ DCs expressed higher levels of activation markers (CD40, CD83, CD86, HLA-DR, and CCR7) than did PB CD1c+ DCs, and higher frequencies of LP CD1c+ DCs constitutively produced IL-6 and -10 and TNF-alpha. LP DCs had blunted cytokine responses to TLR4 ligand and TLR5 ligand stimulation relative to PB DCs, yet similarly produced IL-10 in response to TLR2 ligand. Only synthetic TLR7/8 ligand, a mimic of viral ssRNA, induced IL-23 production by LP CD1c+ DCs, and this proinflammatory cytokine response was synergistically enhanced following combined TLR7/8 and TLR4 stimulation. These findings highlight a potential mechanism by which viruses like HIV-1 may subvert homeostatic mechanisms and induce inflammation in the intestinal mucosa.

Schistosoma mansoni proteins attenuate gastrointestinal motility disturbances during experimental colitis in mice

AIM

To investigate the therapeutic effect of Schistosoma mansoni (S. mansoni) soluble worm proteins on gastrointestinal motility disturbances during experimental colitis in mice.

METHODS

Colitis was induced by intrarectal injection of trinitrobenzene sulphate (TNBS) and 6 h later, mice were treated ip with S. mansoni proteins. Experiments were performed 5 d after TNBS injection. Inflammation was quantified using validated inflammation parameters. Gastric emptying and geometric center were measured to assess in vivo gastrointestinal motility. Peristaltic activity of distal colonic segments was studied in vitro using a modified Trendelenburg set-up. Cytokine profiles of T-lymphocytes isolated from the colon were determined by real time reverse transcriptase-polymerase chain reaction.

RESULTS

Intracolonic injection of TNBS caused severe colitis. Treatment with S. mansoni proteins significantly ameliorated colonic inflammation after 5 d. TNBS did not affect gastric emptying but significantly decreased the geometric center and impaired colonic peristaltic activity 5 d after the induction of colitis. Treatment with S. mansoni proteins ameliorated these in vivo and in vitro motility disturbances. In addition, TNBS injection caused a downregulation of effector T cell cytokines after 5 d, whereas a S. mansoni protein effect was no longer observed at this time point.

CONCLUSION

Treatment with S. mansoni proteins attenuated intestinal inflammation and ameliorated motility disturbances during murine experimental colitis.

Dendritic cell (DC)-specific targeting reveals Stat3 as a negative regulator of DC function

Dendritic cells (DCs) must achieve a critical balance between activation and tolerance, a process influenced by cytokines and growth factors. IL-10, which transduces signals through Stat3, has emerged as one important negative regulator of DC activation. To directly examine the role Stat3 plays in regulating DC activity, the Stat3 gene was targeted for deletion with a CD11c-cre transgene. Stat3 CKO mice developed cervical lymphadenopathy as well as a mild ileocolitis that persisted throughout life and was associated with impaired weight gain. Consistent with this, Stat3-deficient DCs demonstrated enhanced immune activity, including increased cytokine production, Ag-dependent T-cell activation and resistance to IL-10-mediated suppression. These results reveal a cell-intrinsic negative regulatory role of Stat3 in DCs and link increased DC activation with perturbed immune homeostasis and chronic mucosal inflammation.

Molecular modulation of intestinal epithelial barrier: contribution of microbiota

The daunting task required of the gut-barrier to prevent luminal pathogens and harmful substances from entering into the internal milieu and yet promoting digestion and absorption of nutrients requires an exquisite degree of coordination between the different architectural units of this barrier. The complex integration and execution of these functions are superbly carried out by the intestinal mucosal (IM) surface. Exposed to trillions of luminal microbes, the IM averts threats by signaling to the innate immune system, through pattern recognition receptors (PRR), to respond to the commensal bacteria by developing tolerance (hyporesponsiveness) towards them. This system also acts by protecting against pathogens by elaborating and releasing protective peptides, cytokines, chemokines, and phagocytic cells. The IM is constantly sampling luminal contents and making molecular adjustments at its frontier. This article describes the topography of the IM and the mechanisms of molecular adjustments that protect the internal milieu, and also describes the role of the microbiota in achieving this goal.

Oral administration of Alequel, a mixture of autologous colon-extracted proteins for the treatment of Crohn's disease

The pathogenesis of Crohn's disease involves an immune-mediated damage to the gut mucosa. Current developed therapies are based on the use of immunosuppressive drugs that can lead to significant drug-related adverse responses. There is a need for a therapeutic strategy that is more specific and less global in its effect on the immune system. Oral tolerance is an active process wherein oral administration of antigens is associated with the induction of regulatory cells and the suppression of effector cells directed toward specific and nonspecific antigens. Studies in animal models of experimental colitis suggest that oral administration of proteins extracted from the gut can induce tolerance and alleviate the disease symptoms. Recent clinical trials showed that oral administration of Alequel, an autologous protein-containing colon extract, to patients with Crohn's disease is safe and may be effective as a therapeutic modality for treating the disease. This treatment was associated with disease-associated antigen alterations of the immune response in the patients. Oral administration of Alequel could provide a patient-tailored approach that is side-effect-free for the treatment of patients with Crohn's disease.

Proinflammatory Th2 cytokines induce production of thymic stromal lymphopoietin in human colonic epithelial cells

PURPOSE

Thymic stromal lymphopoietin (TSLP) is released by intestinal epithelial cells (IECs), and TSLP-conditioned dendritic cells appear to be involved in immune homeostasis of intestine and immunoglobulin A (IgA) class-switching in the physiological condition. In contrast, TSLP activates dendritic cells to induce strong T-cell proliferation and is involved in inflammatory T helper (Th) 2 responses in human allergic diseases. However, it is not clear how TSLP production by IECs is regulated in ulcerative colitis (UC), which appears to involve inflammatory Th2 responses. The aim of this study is to examine how TSLP production by IECs is regulated in ulcerative colitis.

RESULTS

We show here that expression of TSLP was enhanced in mucosal lesions from UC patients in which inflammatory Th2 cytokine production was predominant. In addition, using a human colonic epithelial cell line, we demonstrated that a combination of tumor necrosis factor-alpha (TNF-alpha) and interleukin-4 (IL-4) induced TSLP expression and that TSLP expression by TNF-alpha + IL-4 was further enhanced by either Toll-like receptor 3 ligand or interferon (IFN)-gamma.

CONCLUSIONS

Taken together, as in human allergic diseases, an inflammatory Th2 condition in the mucosal lesions of UC patients may trigger increased TSLP expression by IECs, resulting in exacerbation of UC.

Oral tolerance: can we make it work?

Mucosal tolerance remains an attractive approach for the treatment of autoimmune and inflammatory diseases. The agents used in these treatments lack toxicity, can be easily administered, and enable the promotion of antigen-specific immune responses. The limited success of clinical trials over the past 2 decades has led to the fear that the beneficial effect observed in animal models cannot be repeated in humans. Successful application of mucosal tolerance for the treatment of human diseases will depend on strategies that target the correct cells in the gut-liver axis, improve antigen presentation, alter the administered dose and formulations, utilize potent mucosal adjuvants, develop immune biomarkers enabling follow-up of the effect, utilize combination therapies with other immune modulatory agents, and target the right patient populations. Here, we discuss 12 of the major questions related to oral tolerance and its clinical application to humans with immune-mediated disorders.

Immunomodulators released during rotavirus infection of polarized caco-2 cells

Rotavirus preferentially replicates in enterocytes and "danger signals" released by these cells are likely to modulate viral immunity. As a model of these events, we studied selected immunomodulators released during rotavirus infection of polarized Caco-2 cells grown in transwell cultures (TW). At early time points post-infection the virus was detected mainly in the apical side of the TWs, but this tendency was progressively lost concomitantly with disruption of the cell monolayer and cell death. Rotavirus-infected cells released IL-8, PGE(2), small quantities of TGF-beta1, and the constitutive and inducible heat shock proteins HSC70 and HSP70, but not IL-1beta, IL-6, IL-10, IL-12p70, or TNF-alpha. This set of immunomodulators is known to induce a non-inflammatory (non-Th-1) immune response, and may be determining, in part, the relatively low T-cell immune response observed in blood samples after RV infection.

Alterations in myeloid dendritic cell innate immune responses in the Galphai2-deficient mouse model of colitis

BACKGROUND

The G protein alpha subunit type-2 (Galpha(i)2)-deficient mouse develops inflammatory bowel disease (IBD) with increased severity in mice on a 129SvEv (129) background compared to the C57BL/6 (B6) background. Since dendritic cells (DCs) are key cells of innate immunity, we determined whether Galpha(i)2(-/-) DCs have functional defects, influenced by strain background, that predispose to IBD.

METHODS

By breeding these strains to homozygosity for the first time, it became possible to study innate immunity in this animal model with more precision than ever before. Immature DCs were generated using bone marrow monoblasts cultured in the presence of GM-CSF (BMDCs), DC subsets sorted and responses to TLR9 activation were assayed.

RESULTS

In contrast to Galpha(i)2(-/-) B6, Galpha(i)2(-/-) 129 mice display accelerated onset and increased severity of colitis, abnormal mucosal DC distribution, accompanied by preponderance for Th1 and Th17-associated gut cytokine expression. TLR9 activation of BMDCs induces sustained p38 MAPK activation and greater Th1- and Th17-type cytokine secretion in both strains of Galpha(i)2-deficient compared to wildtype BMDCs. However, only B6 Galpha(i)2(-/-) BMDCs concomitantly produces IL-10 while Galpha(i)2(-/-) 129 BMDCs do not.

CONCLUSIONS

Loss of Galpha(i)2 promotes a Th1/Th17 phenotype and relative IL-10 insufficiency in Galpha(i)2(-/-) 129 BMDCs may account for the striking difference in disease.

Role of mucosal dendritic cells in inflammatory bowel disease

The gastrointestinal innate and adaptive immune system continuously faces the challenge of potent stimuli from the commensal microflora and food constituents. These local immune responses require a tight control, the outcome of which is in most cases the induction of tolerance. Local T cell immunity is an important compartment of the specific intestinal immune system. T cell reactivity is programmed during the initial stage of its activation by professional presenting cells. Mucosal dendritic cells (DCs) are assumed to play key roles in regulating immune responses in the antigen-rich gastrointestinal environment. Mucosal DCs are a heterogeneous population that can either initiate (innate and adaptive) immune responses, or control intestinal inflammation and maintain tolerance. Defects in this regulation are supposed to lead to the two major forms of inflammatory bowel disease (IBD), Crohn’s disease (CD) and ulcerative colitis (UC). This review will discuss the emerging role of mucosal DCs in regulating intestinal inflammation and immune responses.

Reduced secretion of YopJ by Yersinia limits in vivo cell death but enhances bacterial virulence

Numerous microbial pathogens modulate or interfere with cell death pathways in cultured cells. However, the precise role of host cell death during in vivo infection remains poorly understood. Macrophages infected by pathogenic species of Yersinia typically undergo an apoptotic cell death. This is due to the activity of a Type III secreted effector protein, designated YopJ in Y. pseudotuberculosis and Y. pestis, and YopP in the closely related Y. enterocolitica. It has recently been reported that Y. enterocolitica YopP shows intrinsically greater capacity for being secreted than Y. pestis YopJ, and that this correlates with enhanced cytotoxicity observed for high virulence serotypes of Y. enterocolitica. The enzymatic activity and secretory capacity of YopP from different Y. enterocolitica serotypes have been shown to be variable. However, the underlying basis for differential secretion of YopJ/YopP, and whether reduced secretion of YopJ by Y. pestis plays a role in pathogenesis during in vivo infection, is not currently known. It has also been reported that similar to macrophages, Y. enterocolitica infection of dendritic cells leads to YopP-dependent cell death. We demonstrate here that in contrast to Y. enterocolitica, Y. pseudotuberculosis infection of bone marrow–derived dendritic cells does not lead to increased cell death. However, death of Y. pseudotuberculosis–infected dendritic cells is enhanced by ectopic expression of YopP in place of YopJ. We further show that polymorphisms at the N-terminus of the YopP/YopJ proteins are responsible for their differential secretion, translocation, and consequent cytotoxicity. Mutation of two amino acids in YopJ markedly enhanced both translocation and cytotoxicity. Surprisingly, expression of YopP or a hypersecreted mutant of YopJ in Y. pseudotuberculosis resulted in its attenuation in oral mouse infection. Complete absence of YopJ also resulted in attenuation of virulence, in accordance with previous observations. These findings suggest that control of cytotoxicity is an important virulence property for Y. pseudotuberculosis, and that intermediate levels of YopJ-mediated cytotoxicity are necessary for maximal systemic virulence of this bacterial pathogen.

The ability of bacterial pathogens to modulate death of infected host cells is an important virulence determinant. For pathogenic members of the genus Yersinia, the type III secreted effector protein YopJ/YopP is required for Yersinia-induced macrophage death. The YopJ protein is expressed by Y. pseudotuberculosis, while the ninety-four percent identical YopP protein is expressed by Y. enterocolitica. Y. enterocolitica infection also triggers YopP-dependent killing of dendritic cells, which are critical antigen presenting cells of the immune system. We demonstrate that in contrast to macrophages, dendritic cells are resistant to Y. pseudotuberculosis-mediated cytotoxicity. However, Y. pseudotuberculosis expressing YopP in place of YopJ was highly cytotoxic toward dendritic cells. This difference in cytotoxicity was attributable to a difference in the delivery of YopJ and YopP into mammalian cells. Furthermore, mutation of two amino acids at the N-terminus of YopJ enhanced its delivery and cytotoxicity. Remarkably, we found that enhancing the cytotoxicity of Y. pseudotuberculosis by expression of YopP led to its attenuation in a mouse model of Yersinia infection. This indicates that optimal virulence for a given pathogen requires careful regulation of virulence properties and highlights the potential evolutionary tradeoffs between cellular cytotoxicity and in vivo virulence.

Current view of the immunopathogenesis in inflammatory bowel disease and its implications for therapy

Although the aetiology of inflammatory bowel disease (IBD) remains unknown, the pathogenesis is gradually being unravelled, seeming to be the result of a combination of environmental, genetic, and immunological factors in which an uncontrolled immune response within the intestinal lumen leads to inflammation in genetically predisposed individuals. Multifactorial evidence suggests that a defect of innate immune response to microbial agents is involved in IBD. This editorial outlines the immunopathogenesis of IBD and their current and future therapy. We present IBD as a result of dysregulated mucosal response in the intestinal wall facilitated by defects in epithelial barrier function and the mucosal immune system with excessive production of cytokines growth factors, adhesion molecules, and reactive oxygen metabolites, resulting in tissue injury. Established and evolving therapies are discussed in the second part of this editorial and at the end of this section we review new therapies to modulate the immune system in patients with IBD.

Division of labor, plasticity, and crosstalk between dendritic cell subsets

For years, dendritic cell (DC) biologists have oscillated between two seemingly antagonistic ideas: functional specialization (division of labor) of DC subsets and plasticity (multitasking). More recently, a third hypothesis is gathering support: crosstalk between functionally distinct DC subsets. This reveals a previously unappreciated hierarchy of organization within the DC system, and provides a conceptual framework to understand how cooperation between functionally distinct, yet plastic, DC subsets can shape adaptive immunity and immunological memory. Here we review the recent advances in this area.

Communicable ulcerative colitis induced by T-bet deficiency in the innate immune system

Inflammatory bowel disease (IBD) has been attributed to overexuberant host immunity or the emergence of harmful intestinal flora. The transcription factor T-bet orchestrates inflammatory genetic programs in both adaptive and innate immunity. We describe a profound and unexpected function for T-bet in influencing the behavior of host inflammatory activity and commensal bacteria. T-bet deficiency in the innate immune system results in spontaneous and communicable ulcerative colitis in the absence of adaptive immunity and increased susceptibility to colitis in immunologically intact hosts. T-bet controls the response of the mucosal immune system to commensal bacteria by regulating TNF-alpha production in colonic dendritic cells, critical for colonic epithelial barrier maintenance. Loss of T-bet influences bacterial populations to become colitogenic, and this colitis is communicable to genetically intact hosts. These findings reveal a novel function for T-bet as a peacekeeper of host-commensal relationships and provide new perspectives on the pathophysiology of IBD.

Commensal bacteria and epithelial cross talk in the developing intestine

Indigenous intestinal microbes have co-evolved with the intestinal immune system to form a symbiotic ecosystem. In the postnatal period, intestinal microbes provide the developing gut with stimuli that are necessary for healthy maturation of the intestinal immune system. Cross talk between the host and commensal microbes is an essential component of gut homeostasis mechanisms also in later life. During recent years, innovative research has shed light on the molecular mechanisms of these interactions.

Late-breaking news from the "4th International Meeting on Inflammatory Bowel Diseases" Capri, 2006

At the "4th International Meeting on Inflammatory Bowel Diseases: on the Way to New Therapies," Capri, 2006, genetics, bacteria-host interactions, immunomodulation, and tissue response were discussed deeply in order to understand, rationalize, and develop novel therapies. About genetics, the importance of a better understanding of the nature of known loci and of the putative associations was stressed. It was confirmed that genotype-phenotype associations in inflammatory bowel disease (IBD) have important clinical and therapeutic implications. The importance of the search for dominant bacterial antigens in chronic immune-mediated intestinal inflammation emerged, as well as knowledge of cellular and molecular mechanisms of bacterial-host interactions. It was discussed how innate and adaptive immunity signaling events can perpetuate chronic inflammation. Signal transduction pathways provide an intracellular mechanism by which cells respond and adapt to environmental stress. The identification of these signals have led to a greater understanding of the pathogenesis of IBD and pointed to potential therapeutic targets. It was shown that immune homeostasis is lost in IBD, resulting in a complex tissue response involving the action of immune and nonimmune cells. The nonimmune tissue response in IBD could be regarded as a new target for control of chronic intestinal inflammation. The changing role of biotherapy in IBD was widely discussed and in particular the anti-TNF-alpha monoclonal antibodies. Granulocyte-colony stimulating factor (GM-CSF) and stem cells therapies were also discussed. The risk-to-benefit ratio of the novel therapies was analyzed in detail. Finally, future directions for basic science and the unmet needs for clinical practice were presented.

Induction of ovalbumin-specific tolerance by oral administration of Lactococcus lactis secreting ovalbumin

BACKGROUND AND AIMS

Obtaining antigen-specific immune suppression is an important goal in developing treatments of autoimmune, inflammatory, and allergic gastrointestinal diseases. Oral tolerance is a powerful means for inducing tolerance to a particular antigen, but implementing this strategy in humans has been difficult. Active delivery of recombinant autoantigens or allergens at the intestinal mucosa by genetically modified Lactococcus lactis (L lactis) provides a novel therapeutic approach for inducing tolerance.

METHODS

We engineered the food grade bacterium L lactis to secrete ovalbumin (OVA) and evaluated its ability to induce OVA-specific tolerance in OVA T-cell receptor (TCR) transgenic mice (DO11.10). Tolerance induction was assessed by analysis of delayed-type hypersensitivity responses, measurement of cytokines and OVA-specific proliferation, phenotypic analysis, and adoptive transfer experiments.

RESULTS

Intragastric administration of OVA-secreting L lactis led to active delivery of OVA at the mucosa and suppression of local and systemic OVA-specific T-cell responses in DO11.10 mice. This suppression was mediated by induction of CD4(+)CD25(-) regulatory T cells that function through a transforming growth factor beta-dependent mechanism. Restimulation of splenocytes and gut-associated lymph node tissue from these mice resulted in a significant OVA-specific decrease in interferon gamma and a significant increase in interleukin-10 production. Furthermore, Foxp3 and CTLA-4 were significantly up-regulated in the CD4(+)CD25(-) population.

CONCLUSIONS

Mucosal antigen delivery by oral administration of genetically engineered L lactis leads to antigen-specific tolerance. This approach can be used to develop effective therapeutics for systemic and intestinal immune-mediated inflammatory diseases.

Staphylococcal enterotoxin B increases TIM4 expression in human dendritic cells that drives naïve CD4 T cells to differentiate into Th2 cells

Aberrant T helper (Th)2 polarization plays a critical role in the pathogenesis of allergic disorders; the etiology remains unclear. Dendritic cells (DCs) express T cell immunoglobulin mucin domain (TIM)4 that ligates TIM1 on CD4 T cells to drive them to become Th2 cells, but the pathogenic source of TIM4 is unknown. Here we report that a significant increase in TIM4 expression in human DCs was observed in response to Staphylococcal enterotoxin B (SEB) stimulation via Toll-like receptor (TLR)2 and nucleotide-binding oligomerization domain (NOD)1 pathway. Coculture SEB-conditioned DCs with naïve CD4 T cells induced Th2 responses that could be abolished using TLR2 or NOD1 or TIM4 or TIM1 with counterpart antibodies or RNA interference. The results demonstrate that Staphylococcus aureus derived SEB promotes the TIM4 production in human DCs. The interaction between TIM4 and TIM1 drives naïve CD4 T cells to develop to Th2 cells.

Importance of microbial colonization of the gut in early life to the development of immunity

The mammalian gastrointestinal tract harbors a complex microbiota consisting of between 500 and 1000 distinct microbial species. Comparative studies based on the germ-free gut have provided clear evidence that the gut microbiota is instrumental in promoting the development of both the gut and systemic immune systems. Early microbial exposure of the gut is thought to dramatically reduce the incidence of inflammatory, autoimmune and atopic diseases further fuelling the scientific viewpoint, that microbial colonization plays an important role in regulating and fine-tuning the immune system throughout life. Recent molecular diversity studies have provided additional evidence that the human gut microbiota is compositionally altered in individuals suffering from inflammatory bowel disorders, suggesting that specific bacterial species are important to maintaining immunological balance and health. New and exciting insights into how gut bacteria modulate the mammalian immune system are emerging. However, much remains to be elucidated about how commensal bacteria influence the function of cells of both the innate and adaptive immune systems in health and disease.

gammadelta T cells: firefighters or fire boosters in the front lines of inflammatory responses

Intradermal inoculation of cloned self-reactive alphabeta T cells into the footpads of mice induced cutaneous graft-versus-host disease (GVHD), and after recovery from GVHD, the epidermis became resistant to subsequent attempts to induce GVHD. Resistance to GVHD was not induced in the epidermis of T-cell receptor delta-deficient (TCRdelta(-/-)) mice that lacked gammadelta T cells bearing canonical Vgamma5/Vdelta1(+)gammadeltaTCRs, known as dendritic epidermal T cells (DETCs), and resistance was restored by reconstitution of these mutant mice with precursors of Vgamma5(+) DETCs. Pulmonary infection by Cryptococcus neoformans induced an increase of gammadelta T cells in the lung, and in comparison with wildtype mice, TCRdelta(-/-) mice eliminated C. neoformans more rapidly and synthesized more interferon-gamma in the lung. In the mouse small intestine, the absence of gammadelta T cells is associated with a reduction in epithelial cell turnover and downregulation of the expression of major histocompatibility complex class II molecules. The protective role of gammadelta T cells was verified in a dextran sodium sulfate-induced inflammatory bowel disease (IBD) model, whereas in a spontaneous model of IBD, gammadelta T cells were involved in the exacerbation of colitis in TCRalpha(-/-) mice. Taken together, in addition to the homeostatic regulation of epithelial tissues, gammadelta T cells appear to play a pivotal role in the modification of inflammatory responses induced in many organs containing epithelia.

Potential uses of probiotics in the neonate

Probiotics are specific microbes that, when consumed, contribute to the management of disease or to reducing the risk of disease. Probiotic bacteria have been shown to have several effects that might be of benefit to the neonate, including: modulating the establishment of intestinal microbiota, degrading antigens, promoting mucosal barrier functions and inhibiting mucosal pathogen adherence, and enhancing the maturation of the innate and adaptive immune systems. Results from clinical trials suggest that specific probiotics might be useful in reducing the risk of necrotising enterocolitis and infectious disease in infancy. In addition, probiotic supplementation commenced in the neonatal period might reduce the risk of atopic disease in later life. These data are preliminary, and a number of issues need to be resolved before general guidelines regarding the use of probiotics in the neonatal period can be given.