Oral tolerance: immune mechanisms and the generation of Th3-type TGF-beta-secreting regulatory cells

Traitements nutritionnels au cours des MICI :où en est-on ?

Protein-energy malnutrition and specific nutrient deficiencies are common in inflammatory bowel diseases (IBD), more particularly in Crohn's disease. In adults, the use of artificial nutrition is indicated in the event of malnutrition, short bowel syndrome, or IBD refractory to all other treatments. In children, enteral nutrition has a place as first-line treatment to avoid side effects of corticosteroids on growth. The use, as a therapeutic tool, of specific nutrients (n-3 fatty acids, glutamine, antioxydant vitamins and minerals, TGF-beta, probiotics...) seems interesting at the pathophysiological level. Nevertheless, these nutrients are still under evaluation and there are not enough available studies to recommend them in clinical routine. A very promising solution is the use of probiotics for the treatment of refractory pouchitis.

Regulatory T-Cells and Autoimmunity

Approximately 20% of the population is affected by autoimmune or inflammatory diseases mediated by an abnormal immune response. A characteristic feature of autoimmune disease is the selective targeting of a single cell type, organ or tissue by certain populations of autoreactive T-cells. Examples of such diseases include rheumatoid arthritis, insulin-dependent diabetes mellitus, and systemic lupus erythematosus (SLE), all of which are characterized by chronic inflammation, tissue destruction and target organ malfunction. Although strong evidence links most autoimmune diseases to specific genes, considerable controversy prevails regarding the role of regulatory T-cell populations in the disease process. These cells are now also believed to play a key role in mediating transplantation tolerance and inhibiting the induction of tumor immunity. Though the concept of therapeutic immune regulation aimed at treating autoimmune pathology has been validated in many animal models, the development of strategies for the treatment of human autoimmune disorders remains in its infancy. The main obstacles to this include the conflicting findings of different model systems, as well as the contrasting functions of regulatory T-cells and cytokines involved in the development of such disorders. This review examines the role of regulatory T-cells in the pathogenesis of autoimmunity and describes the therapeutic potential of these cells for the prevention of immune-mediated pathologies in the future. Although much remains to be learned about such pathologies, a clearer understanding of the mechanisms by which regulatory T-cells function will undoubtedly lead to exciting new possibilities for immunotherapeutics.

Defect of oral tolerance in NC/Nga mice

The NC/Nga mouse is a model animal for human atopic dermatitis. In this study, we investigated oral tolerance induction in NC/Nga mice. In BALB/c mice, oral administration of ovalbumin (OVA) resulted in suppression of both OVA-specific T and B cell responses induced by OVA immunization. In NC/Nga mice, OVA-induced antigen (Ag) -specific T and B cell responses were significantly less than those in BALB/c mice. Furthermore, oral administration of OVA did not suppress OVA-specific immunoresponses in NC/Nga mice. We further examined antibody (Ab) response against food Ag by feeding mice an experimental diet that contained OVA or casein as a protein source. The level of serum OVA or casein-specific IgG was significantly higher in NC/Nga mice than in BALB/c mice. These results indicate that NC/Nga mice have a defect in the induction of oral tolerance. NC/Nga mice can therefore be used as a model for investigating the mechanism of oral tolerance.

Migration rules: functional properties of naive and effector/memory-like regulatory T cell subsets

Suppressor T cells were first described in the early 1970s, but since the hypothetical soluble suppressor factor could not be identified on a molecular level and since appropriate cellular markers were lacking, the suppressor T cell concept vanished for a long time. The discovery by Sakaguchi and co-workers, that the adoptive transfer of CD25+CD4+ -depleted T cells induced several organ-specific autoimmune diseases in immunodeficient recipients, put the suppressor T cell model back into the focus of many immunologists. CD25+CD4+ T cells were named regulatory T cells (Treg) and since then have been intensively characterized by many groups. It has now been well documented in a variety of models that CD25+CD4+ Tregs, in addition to cell-intrinsic peripheral tolerance mechanisms such as anergy induction and peripheral deletion, play indispensable roles in the maintenance of natural self-tolerance, in averting autoimmune responses as well as in controlling inflammatory reactions. However, a number of fundamental questions concerning their origin, mechanism of action, and the sites of suppression remain elusive and are currently a matter of debate. Notably, the potential heterogeneity of Tregs with respect to phenotype and function deserves attention and is a major issue discussed in this review.

The Tim-3 ligand galectin-9 negatively regulates T helper type 1 immunity

Tim-3 is a T helper type 1 (T(H)1)-specific cell surface molecule that seems to regulate T(H)1 responses and the induction of peripheral tolerance. However, the identity of the Tim-3 ligand and the mechanism by which this ligand inhibits the function of effector T(H)1 cells remain unknown. Here we show that galectin-9 is the Tim-3 ligand. Galectin-9-induced intracellular calcium flux, aggregation and death of T(H)1 cells were Tim-3-dependent in vitro, and administration of galectin-9 in vivo resulted in selective loss of interferon-gamma-producing cells and suppression of T(H)1 autoimmunity. These data suggest that the Tim-3-galectin-9 pathway may have evolved to ensure effective termination of effector T(H)1 cells.

Seminal plasma and male factor signalling in the female reproductive tract

In mammals, insemination results in the transmission of seminal factors that act, in the female reproductive tract, to promote sperm survival, to "condition" the female immune response to tolerate the conceptus and to organise molecular and cellular changes in the endometrium to facilitate embryo development and implantation. These events are initiated when signalling agents, including transforming growth factor-beta and other cytokines and prostaglandins secreted by seminal vesicle and prostate glands, interact with epithelial cells in the cervix and uterus to activate cytokine synthesis and to induce cellular and molecular changes resembling a classical inflammatory cascade. The consequences are the recruitment and activation of macrophages, granulocytes and dendritic cells, which have immune-regulatory and tissue-remodelling roles that culminate in improved endometrial receptivity to the implanting embryo. Cytokines elicited by seminal activation have embryotrophic properties and also contribute directly to the optimal development of the early embryo. This review summarises our current understanding of the physiology of responses to seminal plasma in the female reproductive tract and considers the evolutionary significance of seminal plasma in influencing female tissues to promote the success of pregnancy.

Recombinant fowlpox virus forin vitrogene delivery to pancreatic islet tissue

The feasibility of using avipox virus as a vector for gene delivery to islet tissue (adult islets and fetal proislets) was examined using a recombinant fowlpox virus (FPV) engineered to express the reporter gene LacZ (FPV-LacZ). The efficiency of in vitro transduction was dose-dependent and influenced by the donor species and maturation status of the islet tissue. Reporter gene expression in FPV-LacZ-transduced islet grafts was transient (3-7 days) in immunoincompetent nude mice and was not prolonged by in vivo treatment with anti-IFN-gamma mAb. In contrast, FPV-LacZ-transduced NIT-1 cells (a mouse islet beta cell line) expressed the LacZ gene beyond 18 days in vitro. Silencing of transgene expression therefore appeared to occur in vivo and was T cell- and IFN-gamma-independent. Isografts of FPV-LacZ-transduced islets in immunocompetent mice underwent immunological destruction by 7 days, suggesting that either FPV proteins or the reporter protein beta-galactosidase induced an adaptive immune response. Co-delivery of the rat bioactive immunoregulatory cytokine gene TGF-beta to islets using FPV-TGF-beta led to enhanced expression of TGF-beta mRNA in isografts but no long-term protection. Nevertheless, compared to control islet isografts at 5 days, FPV-transduced islets remained embedded in the clotted blood used to facilitate implantation. This phenomenon was TGF-beta transgene-independent, correlated with lack of cellular infiltration, and suggested that the FPV vector transformed the blood clot into a temporary immunological barrier.

Involvement of intestinal dendritic cells in oral tolerance, immunity to pathogens, and inflammatory bowel disease

Dendritic cells (DCs) are composed of a family of cells, now recognized to be essential for innate and acquired immunity. DCs at mucosal surfaces have a particular capacity to induce the differentiation of regulatory T cells producing interleukin-10 (IL-10) and transforming growth factor-beta (TGF-beta) in the steady state (non-infected, non-immunized), yet they retain the capacity to induce effector T cells in response to invasive pathogens. This decision between the induction of active immunity and tolerance will depend on the subpopulation of DC involved and the surface receptors engaged during DC activation and T-cell priming. The local microenvironment will likely play an important role both in defining the DC phenotype and in providing direct signals to responding T cells. Furthermore, DCs in organized mucosal lymphoid tissues preferentially induce the expression of CCR9 and alpha4beta7 on T cells, which results in T-cell homing to the intestinal lamina propria. Finally, DCs may play an important role in the maintenance of abnormal intestinal inflammation either by driving pathogenic T-cell responses in mesenteric lymph nodes or by acting to expand or maintain pathogenic T cells locally at sites of inflammation. In this review, a brief discussion of general issues of DC biology that are pertinent to mucosal immunity is followed by a more in-depth discussion of the phenotype and function of DC populations in the intestine.

Thymic commitment of regulatory T cells is a pathway of TCR-dependent selection that isolates repertoires undergoing positive or negative selection

The seminal work of Le Douarin and colleagues (Ohki et al. 1987; Ohki et al. 1988; Salaun et al. 1990; Coutinho et al. 1993) first demonstrated that peripheral tissue-specific tolerance is centrally established in the thymus, by epithelial stromal cells (TEC). Subsequent experiments have shown that TEC-tolerance is dominant and mediated by CD4 regulatory T cells (Treg) that are generated intrathymically by recognition of antigens expressed on TECs (Modigliani et al. 1995; Modigliani et al. 1996a). From these and other observations, in 1996 Modigliani and colleagues derived a general model for the establishment and maintenance of natural tolerance (MM96) (Modigliani et al. 1996b), with two central propositions: (1) T cell receptor (TCR)-dependent sorting of emergent repertoires generates TEC-specific Treg displaying the highest TCR self-affinities below deletion thresholds, thus isolating repertoires undergoing positive and negative selection; (2) Treg are intrathymically committed (and activated) for a unique differentiative pathway with regulatory effector functions. The model explained the embryonic/perinatal time window of natural tolerance acquisition, by developmental programs determining (1) TCR multireactivity, (2) the cellular composition in the thymic stroma (relative abundance of epithelial vs hemopoietic cells), and (3) the dynamics of peripheral lymphocyte pools, built by accumulation of recent thymic emigrants (RTE) that remain recruitable to regulatory functions. We discuss here the MM96 in the light of recent results demonstrating the promiscuous expression of tissue-specific antigens by medullary TECs (Derbinski et al. 2001; Anderson et al. 2002; Gotter et al. 2004) and indicating that Treg represent a unique differentiative pathway (Fontenot et al. 2003; Hori et al. 2003; Khattri et al. 2003), which is adopted by CD4 T cells with high avidity for TEC-antigens (Bensinger et al. 2001; Jordan et al. 2001; Apostolou et al. 2002). In the likelihood that autoimmune diseases (AID) result from Treg deficits, some of which might have a thymic origin, we also speculate on therapeutic strategies aiming at selectively stimulating their de novo production or peripheral function, within recent findings on Treg responses to inflammation (Caramalho et al. 2003; Lopes-Carvalho et al., submitted, Caramalho et al., submitted). In short, the MM96 argued that natural tolerance is dominant, established and maintained by the activity of Treg, which are selected upon high-affinity recognition of self-ligands on TECs, and committed intrathymically to a unique differentiative pathway geared to anti-inflammatory and antiproliferative effector functions. By postulating the intrathymic deletion of self-reactivities on hemopoietic stromal cells (THC), together with the inability of peripheral resident lymphocytes to engage in the regulatory pathway, the MM96 simultaneously explained the maintenance of responsiveness to non-self in a context of suppression mediating dominant self-tolerance. The major difficulty of the MM96 is related to the apparent tissue specificity of Treg repertoires generated intrathymically. This difficulty has now been principally solved by the work of Hanahan, Kyewski and others (Jolicoeur et al. 1994; Derbinski et al. 2001; Anderson et al. 2002; Gotter et al. 2004), demonstrating the selective expression of a variety of tissue-specific antigens by TECs, in topological patterns that are compatible with the MM96, but difficult to conciliate with recessive tolerance models (Kappler et al. 1987; Kisielow et al. 1988). While the developmentally regulated multireactivity of TCR repertoires (Gavin and Bevan 1995), as well as the peripheral recruitment of Treg among RTE (Modigliani et al. 1996a) might add to this process, it would seem that the establishment of tissue-specific tolerance essentially stems from the "promiscuous expression of tissue antigens" by TEC. The findings of AID resulting from natural mutations (reviewed in Pitkanen and Peterson 2003) or the targeted inactivation (Anderson et al. 2002; Ramsey et al. 2002) of the AIRE transcription factor that regulates promiscuous gene expression on TECs support this conclusion. The observations on the correlation of natural or forced expression of the Foxp3 transcription factor in CD4 T cells with Treg phenotype and function (Fontenot et al. 2003; Hori et al. 2003; Khattri et al. 2003) provided support for the MM96 contention that Treg represent a unique differentiative pathway that is naturally established inside the thymus. Furthermore, Caton and colleagues (Jordan et al. 2001), as well as several other groups (Bensinger et al. 2001; Apostolou et al. 2002), have provided direct evidence for our postulate that Treg are selected among differentiating CD4 T cells with high affinity for ligands expressed on TECs (Modigliani et al. 1996b). Finally, the demonstration by Caramalho et al. that Treg express innate immunity receptors (Caramalho et al. 2003) and respond to pro-inflammatory signals and products of inflammation (Caramalho et al., submitted) brought about a new understanding on the peripheral regulation of Treg function. Together with the observation that Treg also respond to ongoing activities of "naïve/effector" T cells--possibly through the IL-2 produced in these conditions--these findings explain the participation of Treg in all immune responses (Onizuka et al. 1999; Shimizu et al. 1999; Annacker et al. 2001; Curotto de Lafaille et al. 2001; Almeida et al. 2002; Shevach 2002; Bach and Francois Bach 2003; Wood and Sakaguchi 2003; Mittrucker and Kaufmann 2004; Sakaguchi 2004), beyond their fundamental role in ensuring self-tolerance (e.g., Modigliani et al. 1996a; Shevach 2000; Hori et al. 2003; Sakaguchi 2004; Thompson and Powrie 2004). Thus, anti-inflammatory and anti-proliferative Treg are amplified by signals that promote or mediate inflammation and proliferation, accounting for the quality control of responses (Coutinho et al. 2001). In turn, such natural regulation of Treg by immune responses to non-self may well explain the alarming epidemiology of allergic and AID in wealthy societies (Wills-Karp et al. 2001; Bach 2002; Yazdanbakhsh et al. 2002), where a variety of childhood infections have become rare or absent. Thus, it is plausible that Treg were evolutionarily set by a given density of infectious agents in the environment. With hindsight, it is not too surprising that natural Treg performance falls once hygiene, vaccination, and antibiotics suddenly (i.e., 100 years) plunged infectious density to below some critical physiological threshold. As the immune system is not adapted to modern clean conditions of postnatal development, clinical immunologists must now deal with frequent Treg deficiencies (allergies and AID) for which they have no curative or rational treatments. It is essential, therefore, that basic immunologists concentrate on strategies to selectively stimulate the production, survival, and activity of this set of lymphocytes that is instrumental in preventing immune pathology. We have argued that the culprit of this inability of basic research to solve major clinical problems has been the self-righteousness of recessive tolerance champions, from Ehrlich to some of our contemporaries. It is ironical, however, that none of us--including the heretic opponents of horror autotoxicus--had understood that self-tolerance, or its robustness at least, is in part determined by the frequency and intensity of the responses to non-self. In the evolution of ideas on immunological tolerance, the time might be ripe for some kinds of synthesis. First, conventional theory reduced self-tolerance to negative selection and microbial defense to positive selection, while the MM96 solution was the precise opposite: positive selection of autoreactivities for self-tolerance (Treg) and negative selection (of Treg) for ridding responses. In contrast, it would now appear that positive and negative selection of autoreactive T cells are both necessary to establish either self-tolerance or competence to eliminate microbes, two processes that actually reinforce each other in the maintenance of self-integrity. Second, V-region recognition has generally been held responsible for specific discrimination between what should be either tolerated or eliminated from the organism. In contrast again, it would now seem that both processes of self-tolerance and microbial defense (self/non-self discrimination) also operate on the basis of evolutionarily ancient, germ-line-encoded innate, nonspecific receptors (Medzhitov and Janeway 2000) capable of a coarse level of self/non-self discrimination (Coutinho 1975). It could thus be interesting to revisit notions of cooperativity between V-regions and such mitogen receptors, both in single cell functions (Coutinho et al. 1974) and in the system's evolution (Coutinho 1975, 1980) as well. After all, major transitions in evolution were cooperative (Maynard-Smith and Szathmary 1995).

Antigen-induced suppressor T cells from the skin point of view

The rebirth of interest in suppressor T cells has spawned a vast amount of data that shed light on their biology and role in immune system homeostasis. Since the early studies on the naturally occurring CD4+/CD25+ T regulatory cells, much attention has been focused on ways to induce suppressor T cells in vivo. This review discusses the salient features of the induction of antigen-specific suppressor T cells in a T cell receptor (TCR) transgenic mouse model of experimental allergic encephalomyelitis (EAE) in response to epicutaneous immunization with cognate peptide. We discuss the skin environment as a privileged anatomical site for therapeutic intervention against pro-inflammatory auto-immune disorders using non-invasive approaches for antigen delivery.

Regulatory T cell responses: potential role in the control of atherosclerosis

PURPOSE OF REVIEW

Atherosclerosis is an inflammatory disease of the arterial wall where both innate and adaptive Th1-driven immunoinflammatory responses contribute to disease development. Th2-related responses have been shown to be either protective or pathogenic. Thus, it is unclear whether immunoregulatory activity can modulate disease development.

RECENT FINDINGS

Novel subtypes of T cells, called the regulatory T cells, have been shown recently to play a critical role in the maintenance of immunological tolerance against self and non-self antigens and prevent the development of various immunoinflammatory diseases. Preliminary studies suggest a potential role for this type of regulatory T cell response in atherosclerosis.

SUMMARY

Here we present a novel view of the immunoinflammatory response in atherosclerosis where natural and/or adaptive regulatory T cell responses modulate both Th1 and Th2 pathogenic responses and play a central role in counteracting disease initiation and progression.

T cell tolerance induced by therapeutic antibodies

Ever since the discovery of Medawar, over 50 years ago, that immunological tolerance was an acquired phenomenon that could be manipulated in neonatal mice, the ability to induce therapeutic tolerance against autoantigens, allergens and organ grafts has been a major driving force in immunology. Within the last 20 years we have found that a brief treatment with monoclonal antibodies that block certain functional molecules on the surface of the T cell is able to reprogramme the established immune repertoire of the adult mouse, allowing indefinite acceptance of allografts or effective curing of autoimmune diseases. We are only now just beginning to define many of the regulatory mechanisms that induce and maintain the tolerant state with the aim of being able to safely and reliably apply these technologies to human clinical situations.

Starch microparticles as vaccine adjuvant

The demand for new vaccine adjuvants is well documented. New purified antigens from parasites, bacterial or viral pathogens, as well as recombinant subunit antigens and synthetic peptides, are often inherently weak immunogens; therefore, they need some kind of adjuvant to help initiate an immune response. In addition, there are very few adjuvants using the potential of the mucosal immune system, which may play an important role in the defence against air- and food-borne infections. Starch is a natural biocompatible and biodegradable polymer that is suitable for the production of various particulate adjuvant formulations, which can induce mucosal as well as systemic immune responses. This review gives an account of the different starch adjuvants used in immunisation studies. In particular, the properties of polyacryl starch microparticles as an oral vaccine adjuvant that induce protective immune responses in mice challenge experiments are summarised. In addition, a diphtheria booster vaccine has been proposed to be used to proving the concept in man and the possibilities to design an efficient vaccine formulation for human use are discussed.

Microparticles for oral delivery of vaccines

Nonreplicating antigens are poorly immunogenic when given orally, either due to their degradation in the gastrointestinal tract or because they are not efficiently taken up in the gut. Studies in laboratory animals have clearly demonstrated that microparticles can significantly improve the immunogenicity of orally administered antigens. However, the oral delivery of vaccines using microparticles has not been explored extensively in humans and large animals. In this article the progress in oral microparticle antigen delivery will be reviewed and, where possible, studies in humans and large animals will be highlighted. In addition, possible approaches that have the potential to significantly improve microparticle delivery of oral vaccines will be suggested.

Regulation of Microbial Immunity: The Suppressor Cell Renaissance

Regulatory/suppressor cells have become rehabilitated and respectable. They returned as regulators of autoimmunity, but are now acknowledged to critically influence immunity to foreign antigens, such as those found on microbes. This review describes the principal types of regulatory cells that influence immunity to microbes, focusing on viruses. We discuss both the merits and downside of the Treg response during infection. The mechanisms by which Treg are induced, recognize microbes, and exert their function is also discussed. Finally, we examine approaches that might prove useful to manipulate regulatory cell response against infections.

Mucosal immunity and allergic responses: lack of regulation and/or lack of microbial stimulation?

Allergic hyperreactivity is defined as an exaggerated immune response [typically immunoglobulin E (IgE) but also non-IgE mediated] toward harmless antigenic stimuli. The prevalence of allergic disease has increased dramatically during the last 20 years, especially in developed countries. Both genetic and environmental factors contribute to susceptibility to allergy. Evidence has emerged supporting the hypothesis that a reduction in antigenic stimulation brought about by widespread vaccination, improvements in standards of hygiene, and extensive use of antibiotics has contributed to the dysregulation of T-helper 2 cell (Th2) type responsiveness that typifies allergy. Regulation of the inherently Th2-biased mucosal immune response is crucial both to the maintenance of homeostasis at this strategic defensive barrier and to the prevention of allergic disease. The ability of Th1 responses to counter-regulate Th2 reactivity is well characterized. More recently, interest has centered on regulatory T cells, which can suppress both Th1 and Th2 cells through the secretion of immunosuppressive cytokines such as interleukin-10 and transforming growth factor-beta. In this review, we discuss the basic cellular mechanisms of allergic diseases at mucosal surfaces, focusing on allergic responses to food, before examining newer work that suggests the induction of allergic hyperreactivity is due to a deficient immunoregulatory network, a lack of microbial stimulation, or both.

Oral tolerance in the absence of naturally occurring Tregs

Mucosal tolerance prevents pathological reactions against environmental and food antigens, and its failure results in exacerbated inflammation typical of allergies and asthma. One of the proposed mechanisms of oral tolerance is the induction of Tregs. Using a mouse model of hyper-IgE and asthma, we found that oral tolerance could be effectively induced in the absence of naturally occurring thymus-derived Tregs. Oral antigen administration prior to i.p. immunization prevented effector/memory Th2 cell development, germinal center formation, class switching to IgE, and lung inflammation. Oral exposure to antigen induced development of antigen-specific CD4CD25Foxp3CD45RB cells that were anergic and displayed suppressive activity in vivo and in vitro. Oral tolerance to the Th2 allergic response was in large part dependent on TGF-beta and independent of IL-10. Interestingly, Tregs were also induced by single i.p. immunization with antigen and adjuvant. However, unlike oral administration of antigen, which induced Tregs but not effector T cells, i.p. immunization led to the simultaneous induction of Tregs and effector Th2 cells displaying the same antigen specificity.

How do DCs interact with intestinal antigens?

Recent evidence demonstrates that dendritic cells (DCs) can insert dendrites between the epithelial cells that form the barrier protecting the body from the gut contents. Although first observed almost a decade ago, this is a controversial area of DC biology and the physiological importance of this phenomenon is only now being clarified. A recent study by Niess and colleagues shows that this behaviour enables efficient sampling of both invasive and non-invasive bacteria and might enhance the ability of an organism to resist infections by a pathogenic strain of Salmonella.

Association of Circulating Interleukin (IL)-12– and IL-10–Producing Dendritic Cells with Time Posttransplant, Dose of Immunosuppression, and Plasma Cytokines in Renal-Transplant Recipients

BACKGROUND

Interleukin (IL)-12-producing dendritic cells (IL-12+DC) polarize T helper (Th) differentiation toward Th1, whereas IL-10+DC induce Th differentiation toward Th2. We investigated DC and plasma cytokine patterns early and late after transplantation.

METHODS

Twenty-five hospitalized renal-transplant recipients without acute rejection or infection early (<40 days) posttransplant, 32 symptom-free outpatients with long-term functioning transplants (2,762+/-2,423 days posttransplant), and 17 healthy controls were studied. The intracellular production of IL-12 and IL-10 in CD11c+ CD83+ CD40+ DC was measured in freshly obtained whole blood using four-color fluorescence flow cytometry. In addition, plasma cytokine levels were investigated.

RESULTS

Early and late posttransplant patients had significantly lower proportions of IL-12+DC (early: P=0.001; late: P=0.034) and lower ratios of IL-12+/IL-10+DC (early: P=0.0001; late: P<0.0001) than healthy controls. IL-10+DC (P=0.0004) and IL-12+DC (P=0.002) increased with time posttransplant in association with dose reductions of cyclosporine (IL-10+DC: P=0.003; IL-12+DC: P=0.005), methylprednisolone (IL-10+DC: P<0.0001; IL-12+DC: P=0.001) and mycophenolate mofetil (IL-10+DC: P<0.0001; IL-12+DC: P=0.004). Both IL-10+DC and IL-12+DC were associated with low plasma IL-10 (IL-10+DC: P=0.010; IL-12+DC: P=0.011) and high plasma IL-6 (IL-10+DC: P=0.001; IL-12+DC: P=0.009). IL-10+DC were also associated with high plasma levels of IL-3 (P=0.003), interferon (IFN)-gamma (P=0.014), and IL-2 (P=0.058).

CONCLUSION

IL-10+DC and IL-12+DC in peripheral blood are associated with time after transplantation and dosage of immunosuppression. IL-10+DC dominate late posttransplant in the presence of Th1 plasma cytokines (high IFN-gamma and IL-2), high IL-3, and low IL-10. These findings could be a reflection of immunoregulatory processes favoring long-term allograft acceptance.

Control of Type 1 Autoimmune Diabetes by Naturally Occurring CD4+CD25+Regulatory T Lymphocytes in Neonatal NOD Mice

Nonobese diabetic (NOD) mice serve as a model of spontaneous type 1 diabetes (T1D), a T cell-mediated autoimmune disease leading to the destruction of pancreatic insulin-producing beta islet cells. A possible deficiency in regulatory T (T(reg)) cell development or function may promote the activation, expansion, and recruitment of autoreactive T cells and the onset of T1D. Naturally occurring CD4(+)CD25(+) T(reg) (nT(reg)) cells, which typically display potent inhibitory effects on T cell functions in vitro and in vivo, may be defective at controlling autoimmunity in T1D. We have examined the relative contribution of CD4(+)CD25(+) nT(reg) cells in the immune regulation of T1D in the NOD mouse model. CD4(+)CD25(+) T cells represent 5-10% of CD4(+) thymocytes or peripheral T cells from prediabetic neonatal NOD mice, are anergic to TCR signals, and potently suppress activated T cells in a contact-dependent and cytokine-independent fashion in vitro. Unlike total CD4(+) T cells, prediabetic CD25(+)-depleted CD4(+) T cells are potently diabetogenic when transferred in immunodeficient NOD mice. Co-transfer of CD4(+)CD25(+) T cells from thymocytes or peripheral lymphoid tissues of neonatal NOD mice dramatically halts disease development and beta-islet cell lymphocytic infiltration, even when T1D is induced by CD4(+) T cells from BDC2.5 transgenic or diabetic NOD mice. Finally, we show that CD4(+)CD25(+) T(reg) preferentially accumulate in inflamed pancreatic environments, where they potently inhibit the antigen-specific expansion and cytokine effector functions of diabetogenic T cells. Thus, CD4(+)CD25(+) T cell-mediated regulation is operative in the prediabetic neonatal T cell repertoire and can suppress the diabetogenic process and control the onset of T1D.

Induction of immune tolerance: a role for Natural killer T lymphocytes?

The ability of the immune system to distinguish between harmful and harmless antigens is essential for mounting protective immune responses and preventing the induction of pathology. Tolerance is a mechanism that prevents or suppresses potentially injurious immune responses. Natural killer T (NKT) lymphocytes, a subset of regulatory T lymphocytes, can induce pro-inflammatory or anti-inflammatory immune responses. This subset of cells appears to be crucial for induction of tolerance by several immune-modulatory interventions; these include immune manipulations in the setting of transplantation, induction of tolerance by introduction of antigen into immune-privileged sites, and oral administration of disease-associated-antigen. The ability to predict whether tolerance or immunity will be generated in a given situation is essential for development of NKT lymphocyte-based immune-modulatory treatments. The role of NKT lymphocytes in these settings, and the requirements for development of tolerance, rather than immunity, are discussed.

T-Helper 2 and 3 type immunity to trophoblast in successful in vitro fertilization-embryo transfer

OBJECTIVE

To determine whether peripheral blood mononuclear cell (PBMC) secretion of T-helper (Th)-1 type cytokines and Th-2 and Th-3 type cytokines in women undergoing in vitro fertilization-embryo transfer (IVF-ET) is associated with therapeutic failure and success, respectively.

DESIGN

Cohort study.

SETTING

Academic medical center.

PATIENT(S)

One hundred one women undergoing IVF-ET and 19 fertile controls.

INTERVENTION(S)

Peripheral blood was obtained from women undergoing IVF-ET before oocyte retrieval and from 19 nonpregnant fertile controls. The PBMCs were cultured in the presence or absence of a protein extract from either a trophoblast cell line or sperm membrane.

MAIN OUTCOME MEASURE(S)

Supernatants from PBMC cultures were tested by enzyme-linked immunoabsorbent assay (ELISA) for the Th-1 type cytokines tumor necrosis factor-alpha (TNF)-alpha) and interferon-gamma (IFN)-gamma), the Th-2 type cytokines interleukin (IL)-6 and IL-10, and the Th-3 type cytokine transforming growth factor (TGF)-beta1.

RESULT(S)

Levels of IL-6 and IL-10 were significantly higher in controls than in infertile women with endometriosis, and levels of IL-10 were higher in controls than in women with unexplained infertility. No differences were found in unstimulated levels of TNF-alpha, IFN-gamma, or TGF-beta1 between infertile patients and controls. In trophoblast-stimulated PBMC cultures, levels of TGF-beta1 were significantly lower in subjects who experienced failed compared with ongoing pregnancies.

CONCLUSION(S)

Baseline PBMC secretion of IL-6 and IL-10 is higher in fertile controls than in women with endometriosis, and IL-10 secretion is also higher than in women with unexplained infertility. Trophoblast-stimulated PBMC secretion of TGF-beta1 is positively associated with the establishment of successful pregnancy in women undergoing IVF-ET. Our study provides novel evidence to support a faciliatory role of Th-2 and Th-3 type responses to trophoblast in early pregnancy.

Ovalbumin-specific IgE modulates ovalbumin-specific T-cell response after repetitive oral antigen administration

BACKGROUND

Some patients outgrow their food allergies even though their serum antigen-specific IgE levels remain high.

OBJECTIVE

To elucidate the role of T cells in outgrowing food allergies in the presence of antigen-specific IgE, we tracked antigen-specific T-cell responses after oral antigen administration.

METHODS

Ovalbumin (OVA)-specific T-cell receptor (TCR) and OVA-specific IgE transgenic (Tg) mice (OVA-TCR/IgE-Tg) and OVA-specific TCR Tg (OVA-TCR-Tg) mice were fed with high doses of OVA or PBS every other day. After 7 administrations, OVA-specific proliferation and cytokine production of mononuclear cells of the spleen, mesenteric lymph nodes, and Peyer's patches and the number of splenic CD4 + CD25 + T cells were analyzed.

RESULTS

Without OVA administration, the splenocytes from OVA-TCR/IgE-Tg mice exhibited a higher proliferative response and produced more IL-4 and IL-10 and less IFN-gamma than those from OVA-TCR-Tg mice. The proliferative responses of the splenocytes from either OVA-TCR/IgE-Tg mice or OVA-TCR-Tg mice fed with OVA were significantly reduced compared with those from PBS-fed mice. The number of OVA-specific TCR + T cells decreased in the spleen from OVA-fed mice, whereas the number of CD4 + CD25 + T cells increased. The suppressed proliferation of splenocytes of OVA-fed mice was partially resumed by neutralization of TGF-beta1, but not of IL-10.

CONCLUSION

The presence of OVA-specific IgE modulated the OVA-specific responses of the splenocytes. Irrespective of the presence of OVA-specific IgE, repetitive oral administration of OVA induced tolerance, which seems to be composed of clonal deletion/anergy and TGF-beta1-mediated active suppression.

The role of regulatory T cell defects in type I diabetes and the potential of these cells for therapy

Type I diabetes is increasing in incidence in developed countries [1]. Diabetes arises from a breakdown of tolerance to islet antigens, resulting in T cell-driven destruction of the islet cells and concomitant hyperglycemia. In this review, we explore whether this loss of tolerance results in part from a defect in the action of regulatory T cells. We draw on both human data and that obtained from NOD mice, the murine model of autoimmune diabetes. Although insulin-based therapies have been highly successful in treating diabetes, the complications of long-term hyperglycemia are still major causes of morbidity and mortality. Accordingly, we also discuss whether treatment with regulatory T cells is a viable method for restoring long-term tolerance to self-antigens in recently diagnosed or pre-diabetic individuals. Regulatory T cell therapy offers many potential advantages, including a specific and lasting dampening of inflammation. However, some significant hurdles would have to be overcome before it could become an established treatment.

T lymphocytes and food allergy

Food allergy is a hypersensitivity reaction to normally harmless substances and involves humoral immune responses, mediated by immunoglobulin (IgE) synthesized by B lymphocytes, and cellular immune responses mediated by T lymphocytes. An IgE-mediated mechanism leads to clinical symptoms occurring immediately after food ingestion, e. g., "the oral allergy syndrome". For delayed reactions involving the gastrointestinal tract or the skin, the underlying immune mechanisms are less clear. In order to elucidate the cellular response to food allergens, human allergen-specific T cell cultures generated in vitro represent helpful tools. The majority of food allergen-specific CD4(+) T lymphocytes isolated from food-allergic individuals was found to synthesize high levels of IL-4 and IL-13, two cytokines required for initiation of IgE synthesis. Due to selective homing profiles, food-specific T cells seem also to be involved in defining the target organ of the allergic inflammation. Recent data provide evidence that in addition to IgE-mediated inflammation, food allergen-specific T lymphocytes may also cause inflammatory responses independently of IgE-mediated mechanisms.

Fimbriae of enterotoxigenic Escherichia coli function as a mucosal carrier for a coupled heterologous antigen

Receptor-mediated uptake of orally administered antigen can lead to an antigen-specific immune response, whereas oral administration of most other non-replicating soluble antigens results in the induction of oral tolerance. In the present study, it is shown that fimbriae purified from an F4(K88)(+) enterotoxigenic Escherichia coli strain can function as a mucosal carrier molecule for the model antigen human serum albumin (HSA). Glutaraldehyde-coupled F4/HSA conjugates were able to bind F4 receptor positive (F4R(+)) enterocytes, but not to F4R(-) enterocytes. Moreover, oral immunization of F4R(+) pigs with F4/HSA conjugates induced a HSA-specific immune response, whereas oral immunization with HSA/HSA conjugates did not. This mucosal carrier function of F4 fimbriae was improved following oral co-administration of the F4/HSA conjugates with the mucosal adjuvant cholera toxin (CT) to F4R(+) pigs, since both humoral and cellular HSA-specific responses were significantly increased. In comparison with F4R(+) pigs, the HSA-specific response was reduced following oral F4/HSA+CT immunization of F4R(-) pigs. This indicates that F4 fimbriae as mucosal carrier and CT as adjuvant synergistically improve the induction of a HSA-specific immune response following oral immunization of pigs. These results could open new perspectives in the development of vaccines against enteropathogens.

The role of the T cell in autoimmune inflammation

T cells, in particular CD4⁺ T cells, have been implicated in mediating many aspects of autoimmune inflammation. However, current evidence suggests that the role played by CD4⁺ T cells in the development of rheumatoid inflammation exceeds that of activated proinflammatory T-helper (Th)1 effector cells that drive the chronic autoimmune response. Subsets of CD4⁺ T cells with regulatory capacity, such as CD25⁺ regulatory T (Treg) cells and Th2 cells, have been identified, and recent observations suggest that in rheumatoid arthritis the function of these regulatory T cells is severely impaired. Thus, in rheumatoid arthritis, defective regulatory mechanisms might allow the breakdown of peripheral tolerance, after which the detrimental Th1-driven immune response evolves and proceeds to chronic inflammation. Here, we review the functional abnormalities and the contribution of different T cell subsets to rheumatoid inflammation.

Antigen-based immunointervention in human autoimmune diseases

Antigen administration can ameliorate autoimmune disease via various mechanisms, including deletion of autoreactive cells, induction of regulatory T cells, and deviation to non-pathogenic or protective responses. All these mechanisms of immunointervention have been successfully used to prevent and sometimes treat experimental models of autoimmune diseases. Based on these results, expectations have been raised for exploiting similar strategies to inhibit pathogenic autoreactive T cells in human autoimmune diseases. Among them, mucosal administration of autoantigen is an attractive mode of immunointervention still awaiting demonstration of clinical efficacy in human autoimmune diseases. A further step in this direction is now provided by the clear-cut immune deviation observed following oral administration of a disease-related peptide to rheumatoid arthritis patients, leading to inhibition of Th1 while enhancing Th2 and possibly Foxp3-positive regulatory T cells.

Antigens up the nose: identification of putative biomarkers for nasal tolerance induction functional studies combined with proteomics

Intranasal autoantigen delivery is the most effective means of inducing mucosal tolerance and suppression of autoimmune disease. In an effort to identify markers of the "tolerant state", we employed proteomics technology at the level of the cervical lymph node. The analysis revealed that nasal antigen administration (without adiuvant) led to modulation of various proteins among which the most prominent were haptoglobin, nonintegrin 67 kDa laminin receptor, and MRP8. The immunoregulatory haptoglobin may qualify as (bio)marker for effective immunotherapy.

Regulatory T cells in rheumatoid arthritis

Apart from the deletion of autoreactive T cells in the thymus, various methods exist in the peripheral immune system to control specific human immune responses to self-antigens. One of these mechanisms involves regulatory T cells, of which CD4+CD25+ T cells are a major subset. Recent evidence suggests that CD4+CD25+ T cells have a role in controlling the development of autoimmune diseases in animals and in humans. The precise delineation of the function of CD4+CD25+ T cells in autoimmune inflammation is therefore of great importance for the understanding of the pathogenesis of autoimmune diseases. Moreover, the ability to control such regulatory mechanisms might provide novel therapeutic opportunities in autoimmune disorders such as rheumatoid arthritis. Here we review existing knowledge of CD4+CD25+ T cells and discuss their role in the pathogenesis of rheumatic diseases.

Bystander Effect in Synergy to Anergy in Oral Tolerance of Blomia Tropicalis/Ovalbumin Murine Co-Immunization Model

Oral tolerance is an important approach in allergic diseases and murine model can provide useful information to improve its understanding and therapeutic measures. To address the influence of non-related allergen sensitization in immunized mice with the mite Blomia tropicalis (Bt) or ovalbumin (OVA) or with both Bt/OVA allergens. Furthermore, we sought to verify oral tolerance effect in the Bt/OVA co-immunization model. Mice sensitized with Bt and then exposed to OVA developed an enhanced IgE response to both allergens; contrariwise, this effect was not observed when OVA-sensitization was prior to Bt-sensitization. Co-injection of Bt and OVA led to a dominant IgE response towards OVA over Bt, which was not observed when co-immunization was performed with a 240-fold less amount of OVA. Induction of oral tolerance with OVA, prior to co-immunization, suppressed IgE response to both allergens, probably as a consequence of the increased levels of IFN-gamma found in these animals. The results evidenced that, depending on allergenic potential, new allergen exposure may exert an adjuvant effect to the first allergen used in the sensitization. The bystander suppression to non-related allergens through oral tolerance should be a useful mechanism to control sensitization to new allergens.

Alleviation of chronic GVHD in mice by oral immuneregulation toward recipient pretransplant splenocytes does not jeopardize the graft versus leukemia effect

Chronic graft versus host disease (cGVHD) is the result of an immune-mediated attack by transplanted donor lymphocytes, entailing inflammatory damage to host target organs. Clinically, the post-bone marrow transplantation (BMT) graft versus leukemia (GVL) effect may be associated with GVHD. Immune hyporesponsiveness induced by oral antigen administration has recently been shown to prevent the development of cGVHD in a murine model. To evaluate whether amelioration of cGVHD in mice by induction of oral immune regulation in donors toward recipient pretransplant lymphocyte antigens is associated with attenuation of the GVL effect donor B10.D2 mice were fed with Balb/c splenocytes, B10.D2 splenocytes, bovine serum albumin (BSA), or regular chow, every other day for 10 days. Subsequently, transplantation of 2 x 10(7) splenocytes from donor B10.D2 mice to recipient Balb/c mice was undertaken, followed by inoculation of 3 x 10(3) BCL-1 leukemia on the day of BMT. Control groups were fed identically without leukemia inoculation. Mice were followed for survival and leukemia progression. Induction of tolerance was assessed by a mixed lymphocyte reaction (MLR). Cutaneous GVHD was assessed macroscopically. To elucidate the mechanism of any observed effect, serum interferon (IFN), interleukin (IL-2), IL-12, IL-4, and IL-10 were determined by enzyme-linked immunosorbent assay and flow cytometry analysis for CD4+, CD8+, and NK1.1+ lymphocyte subpopulations was performed. There was no significant difference in leukemia progression manifested by survival or white blood cell counts of orally immune-regulated mice compared with control animals. Cutaneous cGVHD was significantly ameliorated in Balb/c mice transplanted from tolerized B10.D2 mice. This effect was associated with a significant reduction in the mixed lymphocyte response of effector splenocytes from tolerized B10.D2 mice against Balb/c target splenocytes; significantly decreased serum IFN-gamma and IL-2; increased serum IL-12 levels; increased peripheral NK1.1+ cells; and CD4+/CD8+ lymphocyte ratio. Oral tolerization of BMT donors toward recipient antigens ameliorates cGVHD without hampering the GVL effect.

B cells are not required for T cell priming in low zone tolerance to contact allergens and contact hypersensitivity

Low zone tolerance (LZT) to contact allergens is induced by epicutaneous exposure to haptens in subsensitizing doses resulting in an inhibition of contact hypersensitivity (CHS), which, in contrast, occurs after sensitization with immunogenic doses of allergens. Performing the protocol of tolerance induction resulted in robust LZT to allergens in B cell-deficient mice in vivo, indicating that B cells are not required for the induction and effector phase of LZT. However, CHS reactions in vivo were restricted in B cell-deficient mice as compared to wild-type (WT) mice. In contrast, analysis of hapten-specific T cell activation in vitro revealed a strong proliferative response of T cells derived from both WT and B cell-deficient sensitized mice. Similar to WT animals, T cells obtained from tolerized B cell-deficient mice produced a Tc2 cytokine pattern of LZT with high levels of IL-4 and IL-10, whereas sensitization of B cell-deficient mice resulted in the typical Tc1 cytokine profile of CHS. Adoptive transfer of CD8+ effector T cells from tolerized or sensitized B cell-deficient mice induced significant LZT or CHS reactions, respectively, in WT recipients, demonstrating that the development of hapten-specific effector CD8+ T cells of LZT and CHS is independent of B cells.

Cell therapy for autoimmune diseases: does it have a future?

Almost all current therapeutic concepts in autoimmune diseases are based on the systemic suppression of immune functions and are not curative. The recent introduction of biologicals such as tumour necrosis factor blocking antibodies or receptors has added greater specificity to efficient management of disease by targeted suppression of rheumatic inflammation. It is evident, however, that only the elimination of the cells secreting inflammatory mediators, rather than the blockade of secreted molecules, will offer real specific therapeutic advantages in the future. Merely the elimination of such cells and also cells controlling the secreting effector cells could be curative and induce true long term remissions. We review here the state of the art and future therapeutic concepts that are based on the specific modulation of pathogenic cells that induce and sustain autoimmune inflammation. This sounds visionary, however, a variety of basic tools are at hand now. Thus, direct and specific cell therapy of rheumatic diseases will become a true alternative to conventional therapies.

Oral Immune Regulation toward Disease-Associated Antigens: Results of Phase I Clinical Trials in Crohn's Disease and Chronic Hepatitis

Oral immune regulation is an immune response toward orally administered antigens, and is a balance between several types of responses. Recent studies in animal models have shown that antiviral immunity and the immune response toward colonic proteins can be modulated by oral feeding of these antigens. The effect of oral immune regulation on the outcome of various immune-mediated processes, including infectious, inflammatory, and neoplastic entities, has been the subject of much research and debate in recent years. Two phase I clinical trials have evaluated the effect of oral immune regulation in patients with chronic hepatitis B virus infection and Crohn's disease. Mechanisms and possible future clinical applications of this immune modulatory method are discussed.

Oral immune regulation: a novel method for modulation of anti-viral immunity

Chronic viral infections, including hepatitis B and C and human immunodeficiency virus (HIV) infections, afflict a significant part of the world's population. In many of these diseases, chronicity has been linked to defective anti-viral immunity that damages host tissues without producing viral clearance. Currently available therapeutic measures for chronic viral infections are limited. Oral immune regulation, the manipulation of immune responses towards antigens by their oral administration, is a relatively simple and antigen-specific immune-modulatory tool. Recent evidence suggests that induction of oral immune-regulation towards viral antigens may entail a complex immune effect, characterized by simultaneous enhancement and suppression of different elements of the immune response in a manner that benefits the host. Such manipulation of the immune response towards viruses may achieve a combination of upregulated specific anti-viral immunity and inhibition of immune-mediated damage. Oral immune regulation may prove to be an important addition to the available therapeutic arsenal for chronic viral infections.

HLA class I noninherited maternal antigens in cord blood and breast milk

Maternally induced allotolerance both in clinical and experimental organ transplantation appears to require both in utero and oral exposure to noninherited maternal antigens (NIMA). Soluble major histocompatibility complex (MHC) class I antigens were studied in 18 mother-baby pairs in order to determine the extent of neonatal exposure to NIMA. Enzyme-linked immunoabsorbent assay (ELISA) analysis of cord blood from three genetically HLA-A2 negative babies born to HLA-A2+ mothers and from two HLA-A3 negative babies born to HLA-A3+ mothers revealed significant NIMA HLA-A levels in cord plasma. The level of NIMA-A2 or -A3 in cord blood were approximately 10% of the predicted value for a baby genetically positive for that allele. HLA-A2 or -A3 was undetectable (< 1.0 ng/ml) in cord blood from HLA-A2 or -A3 negative babies whose mothers were also HLA-A2 or -A3 negative. Breast milk from HLA-A2+ mothers contained soluble HLA-A2 (sHLA-A2) at levels averaging 36.2 ng/ml, resulting in milligram quantities of ingested antigen over 3 months of nursing. Western blot analysis of cord plasma confirmed that bands corresponding to NIMA HLA-A protein were present. This study demonstrates that oral and intravenous exposure to NIMA sHLA in the fetus and newborn is much higher than previously thought, and emphasizes the importance of nursing in the overall antigen dose achieved.

Characterization of breast milk received by infants with gross blood in stools

OBJECTIVE

The aim of this study was to ascertain factors that might be protective of the appearance of gross blood in the stools of breast-fed infants.

METHODS

Logistic regression models were formed to search for variables possibly explaining the condition. In addition to the analyzed breast milk factors, mother's allergic disease was introduced into the models to control for its possible confounding effect. The breast milk samples, collected from mothers of infants with gross blood in stools (n = 23) and from mothers of healthy age-matched infants (n = 71), were analyzed for concentrations of transforming growth factor-beta2, tumor necrosis factor-alpha, interleukin (IL)-4, IL-10, prostaglandin (PG)E2, cysteinyl leukotrienes (Cys-LTs) and fatty acid composition.

RESULTS AND CONCLUSIONS

Increase in the concentrations of PGE2 and Cys-LTs in the breast milk together with mother's allergic disease reduced the likelihood of gross blood in stools in the breast-fed infant. The results suggest that no single factor, but a combination of immunomodulatory factors may protect the child from gross blood in the stools of breast-fed infants. Allergic disease was not a risk factor as mother's allergic disease appeared to counterbalance the gross blood in stools. Due to the preliminary nature of the study, the results need to be verified in a larger setting. The challenge for the future lies in identifying of such active compounds for dietary modification to enforce particularly the properties of the breast milk which are immunoprotective for the infant and to reduce the likelihood of intestinal disorders in at risk infants.

Cow's milk allergy in infants with atopic eczema is associated with aberrant production of interleukin-4 during oral cow's milk challenge

OBJECTIVES

A failure in the establishment and maintenance of oral tolerance in infancy may result in food allergy. To further assess the role of the intestinal immune system in cow's milk allergy (CMA), we investigated the systemic production of the pro-allergenic Th2 cytokine interleukin (IL)-4 and anti-allergenic cytokines IL-10, transforming growth factor (TGF)-beta1 and TGF-beta2 in infants suffering from atopic eczema with and without CMA during antigen elimination diet and oral antigen exposure.

METHODS

18 infants (mean age, 9.6 months; 95% confidence interval 8.1-11.1 months) with atopic eczema and CMA and 17 infants (mean age, 9.7 months; 95% confidence interval 8.6-10.9 months) with atopic eczema tolerant to milk as assessed by a double blind, placebo-controlled cow's milk challenge were investigated. Peripheral blood mononuclear cells were obtained during antigen elimination diet and during oral cow's milk challenge and stimulated with Concanavalin-A or cow's milk or were left unstimulated. The cytokine concentrations were measured by enzyme-linked immunosorbent assay.

RESULTS

During antigen elimination, the Concanavalin A-stimulated production of TGF-beta2 was significantly lower in infants with CMA as compared with infants without CMA: 129 pg/mL (interquartile ratio, 124-144 pg/mL) vs. 149 pg/mL (interquartile ratio, 133-169 pg/mL); P = 0.016. During oral antigen exposure, the immune responses in infants with CMA were characterized by significantly higher spontaneous production of IL-4 as compared with those without CMA: 12.0 pg/mL (interquartile ratio, 5.2-28.3 pg/mL) vs. 4.2 pg/mL (interquartile ratio, 1.5-7.6 pg/mL); P = 0.018.

CONCLUSIONS

Infants with atopic eczema and CMA exhibit markedly increased systemic pro-allergenic IL-4 responses on intestinal antigen contact, which may partially be explained by a defective ability to launch anti-allergenic TGF-beta2 responses.

Stimulation of interleukin-10 production by acidic beta-lactoglobulin-derived peptides hydrolyzed with Lactobacillus paracasei NCC2461 peptidases

We have previously demonstrated that Lactobacillus paracasei NCC2461 may help to prevent cow's milk allergy in mice by inducing oral tolerance to beta-lactoglobulin (BLG). To investigate the mechanisms involved in this beneficial effect, we examined the possibility that L. paracasei induces tolerance by hydrolyzing BLG-derived peptides and liberating peptides that stimulate interleukin-10 (IL-10) production. L. paracasei peptidases have been shown to hydrolyze tryptic-chymotryptic peptides from BLG, releasing numerous small peptides with immunomodulating properties. We have now shown that acidic tryptic-chymotryptic peptides stimulate splenocyte proliferation and gamma interferon (IFN-gamma) production in vitro. Hydrolysis of these peptides with L. paracasei peptidases repressed the lymphocyte stimulation, up-regulated IL-10 production, and down-regulated IFN-gamma and IL-4 secretion. L. paracasei NCC2461 may therefore induce oral tolerance to BLG in vivo by degrading acidic peptides and releasing immunomodulatory peptides stimulating regulatory T cells, which function as major immunosuppressive agents by secreting IL-10.

Antigen-tailored therapy based on the inflammatory theory of atherosclerosis

In recent years, considerable data has been provided to support the role of the immune system in atherosclerosis. These reports came from studies involving knockout murine models of atherosclerosis and human subjects. The notion that inflammatory mechanisms are operable in atherogenesis has fueled a series of studies demonstrating that autoimmune responses are also evident in the atherosclerotic lesions and appear to influence the initiation and progression of the plaque. The principal autoantigens that have been suggested as potential triggers of autoimmune responses in atherosclerosis are modified forms of low-density lipoproteins, heat shock proteins and beta2 glycoprotein I. Immunization against these antigens influenced the generation of lesions and adoptive transfer studies of lymphocytes reactive to some of these antigens have also been demonstrated to enhance the growth of the plaques. The realization that autoimmune-like responses may play a role in the progression of atherosclerotic lesions has paved the way for exciting modes of manipulating lesions, irrespective of the effect on the lipid profile. Thus, recent studies indicate that oral tolerance with antigens or derivatives could suppress the respective immune responses and reduce the extent of the lesions in transgenic atherosclerosis-prone mice. These observations should be further explored and if validated, could represent novel modalities for influencing atherogenessis in humans.

Animal models of type I allergy using recombinant allergens

Various animal models including guinea pigs, monkeys, dogs, rats, and mice have been established in an attempt to provide insights into the complex immunological and pathophysiological mechanisms of human type I allergic diseases. The detailed knowledge of the murine genome, the various components of the murine immune system, and the generation of engineered mice has made the murine system the most attractive among all animal models. The availability of multitude technologies and reagents to characterize and manipulate immunological pathways and mediators adds to the outstanding opportunities to assess the pathology of allergic diseases and to develop novel therapeutic strategies in mice. Numerous sensitization protocols with food and aero-allergens are used to establish an allergic/asthma-like phenotype in mice. Requirements for an appropriate murine model include a close resemblance to the pathology of the disease in humans, the objective measurement of the physiologic parameters, as well as reliability and reproducibility of the experimental data. With respect to reproducible experimental conditions, it has been recognized that extract preparations from natural allergen sources can vary in their allergen-content and -composition. This might influence the degree of sensitization or the outcome of treatment strategies in dependence of the applied extract preparation. The use of recombinant allergens in experimental in vivo and in vitro systems can overcome these problems. Another aspect, that has become obvious from the experimental studies, is that allergens can differ in their immunogenicity as well as in their capacity to act as tolerogens. Therefore, it seems important that the efficacy of the different allergen-molecules to act as therapeutic agents is individually examined. In this review, examples of animal models are described, in which recombinant allergens have been used for sensitization and/or treatment of allergic responses and how they have been used to enhance our understanding of the pathology of allergic diseases.

Regulatory cells and infectious agents: detentes cordiale and contraire

This brief review describes the types of interactions that occur between CD4(+)CD25(+) regulatory T cells (Treg) and microbial pathogens. These interactions range from one of mutual benefit (détente cordiale) such as occurs in Leishmania major infection of resistant mouse strains, to instances where the Treg response appears to mainly favor the pathogen and be detrimental to the host (détente contraire). Examples of the latter include chronic persistent infections with retroviruses, perhaps including HIV, and hepatitis C virus. The Treg response also hampers the effectiveness of immunity against some acute virus infections such as HSV. Evidence is also discussed showing that Treg can play a benevolent role to limit the severity of bystander tissue damage in circumstances where the immune response to pathogens is immunopathological. Finally, emerging approaches are discussed that either blunt or activate Treg and that could be used practically to manage host-pathogen interaction.