Neonatal peptide exposure can prime T cells and, upon subsequent immunization, induce their immune deviation: implications for antibody vs. T cell-mediated autoimmunity

Lymph node stromal cell responses to perinatal T cell waves, a temporal atlas

The perinatal period is a critical time window in establishing T cell tolerance. Regulatory T cells (Tregs) made during the first 2 wk of life are key drivers of perinatal tolerance induction, but how these cells are generated and operate has not been established. To elucidate the unique environment murine perinatal Tregs encounter within the lymph nodes (LNs) as they first emerge from the thymus, and how it evolves over the succeeding days, we employed single-cell RNA sequencing to generate an atlas of the early LN niche. A highly dynamic picture emerged, the stromal cell compartment showing the most striking changes and putative interactions with other LN cell compartments. In particular, LN stromal cells showed increasing potential for lymphocyte interactions with age. Analogous studies on mice lacking α:β T cells or enriched for autoreactive α:β T cells revealed an acute stromal cell response to α:β T cell dysfunction, largely reflecting dysregulation of Tregs. Punctual ablation of perinatal Tregs induced stromal cell activation that was dependent on both interferon-gamma signaling and activation of conventional CD4+ T cells. These findings elucidate some of the earliest cellular and molecular events in perinatal induction of T cell tolerance, providing a framework for future explorations.

Age-Dependent Differences in T-Cell Responses to Influenza A Virus

Respiratory infections from influenza A virus (IAV) cause substantial morbidity and mortality in children relative to adults. T cells play a critical role in the host response to IAV by supporting the innate and humoral responses, mediating cytotoxic activity, and promoting recovery. There are age-dependent differences in the number, subsets, and localization of T cells, which impact the host response to pathogens. In this article, we first review how T cells recognize IAV and examine differences in the resting T-cell populations between juveniles and adults. Next, we describe how the juvenile CD4⁺, CD8⁺, and regulatory T-cell responses compare with those in adults and discuss the potential physiologic and clinical consequences of the differences. Finally, we explore the roles of two unconventional T-cell types in the juvenile response to influenza, natural-killer T cells and γδ T cells. A clear understanding of age-dependent differences in the T-cell response is essential to developing therapies to prevent or reverse the deleterious effects of IAV in children.

Neonatal T Cells: A Reinterpretation

Neonatal CD4⁺ and CD8⁺ T cells have historically been characterized as immature or defective. However, recent studies prompt a reinterpretation of the functions of neonatal T cells. Rather than a population of cells always falling short of expectations set by their adult counterparts, neonatal T cells are gaining recognition as a distinct population of lymphocytes well suited for the rapidly changing environment in early life. In this review, I will highlight new evidence indicating that neonatal T cells are not inert or less potent versions of adult T cells but instead are a broadly reactive layer of T cells poised to quickly develop into regulatory or effector cells, depending on the needs of the host. In this way, neonatal T cells are well adapted to provide fast-acting immune protection against foreign pathogens, while also sustaining tolerance to self-antigens.

A New IRF-1-Driven Apoptotic Pathway Triggered by IL-4/IL-13 Kills Neonatal Th1 Cells and Weakens Protection against Viral Infection

Early life immune responses are deficient in Th1 lymphocytes that compromise neonatal vaccination. We found that IL-4 and IL-13 engage a developmentally expressed IL-4Rα/IL-13Rα1 heteroreceptor to endow IFN regulatory factor 1 (IRF-1) with apoptotic functions, which redirect murine neonatal Th1 reactivation to cell death. IL-4/IL-13-induced STAT6 phosphorylation serves to enhance IRF-1 transcription and promotes its egress from the nucleus. In the cytoplasm, IRF-1 can no longer serve as an anti-viral transcription factor but, instead, colocalizes with Bim and instigates the mitochondrial, or intrinsic, death pathway. The new pivotal function of IRF-1 in the death of neonatal Th1 cells stems from the ability of its gene to bind STAT6 for enhanced transcription and the proficiency of its protein to precipitate Bim-driven apoptosis. This cytokine-induced, IRF-1-mediated developmental death network weakens neonatal Th1 responses during early life vaccination and increases susceptibility to viral infection.

The neonatal anti-viral response fails to control measles virus spread in neurons despite interferon-gamma expression and a Th1-like cytokine profile

Neonates are highly susceptible to viral infections in the periphery, potentially due to deviant cytokine responses. Here, we investigated the role of interferon-gamma (IFNγ), a key anti-viral in the neonatal brain. We found that (i) IFNγ, which is critical for viral control and survival in adults, delays mortality in neonates, (ii) IFNγ limits infiltration of macrophages, neutrophils, and T cells in the neonatal brain, (iii) neonates and adults differentially express pathogen recognition receptors and Type I interferons in response to the infection, (iv) both neonates and adults express IFNγ and other Th1-related factors, but expression of many cytokines/chemokines and IFNγ-responsive genes is age-dependent, and (v) administration of IFNγ extends survival and reduces CD4 T cell infiltration in the neonatal brain. Our findings suggest age-dependent expression of cytokine/chemokine profiles in the brain and distinct dynamic interplays between lymphocyte populations and cytokines/chemokines in MV-infected neonates.

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The role of the anti-viral cytokine interferon-gamma (IFNγ) is investigated during a neonatal viral infection in CNS neurons.

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IFNγ did not prevent mortality in neonates, but it slowed disease progression.

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IFNγ reduced infiltration of neutrophils, macrophages, and T cells in the neonatal CNS.

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Both adult and neonatal mice expressed Th1-like cytokines, including IFNγ and some IFNγ-stimulated genes, during infection.

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Despite a Th1-like cytokine profile in the neonatal CNS, the cytokine milieu is ineffective at controlling viral spread.

Enhanced immunization techniques to obtain highly specific monoclonal antibodies

Despite fast advances in genomics and proteomics, monoclonal antibodies (mAbs) are still a valuable tool for areas such as the evolution of basic research in stem cells and cancer, for immunophenotyping cell populations, diagnosing and prognosis of diseases, and for immunotherapy. To summarize different subtractive immunization approaches successfully used for the production of highly specific antibodies, we identified scientific articles in NCBI PubMed using the following search terms: subtractive immunization, monoclonal antibody, tolerization, neonatal, high-zone tolerance, masking immunization. Patent records were also consulted. From the list of results, we included all available reports, from 1985 to present, that used any enhanced immunization technique to produce either polyclonal or monoclonal antibodies. Our examination yielded direct evidence that these enhanced immunization techniques are efficient in obtaining specific antibodies to rare epitopes, with different applications, such as to identify food contaminants or tumor cells.

Potential route of Th17/Treg cell dynamics in targeting type 1 diabetes and rheumatoid arthritis: an autoimmune disorder perspective

Cytokines, small secreted proteins, have a specific effect on the interactions and communications between cells. They play a pivotal role in the pathogenesis of autoimmune diseases. Factors in the breakdown of self-tolerance and the subsequent events leading to the induction of pathogenic responses remain unclear for most of the autoimmune diseases. Large numbers of studies have revealed a general scheme in which pro-inflammatory cytokines contribute to the initiation and propagation of autoimmune inflammation, whereas anti-inflammatory cytokines facilitate the regression of inflammation and thereby recovery from the disease. The interleukin (IL)-17/IL-23 axis that emerged as the new paradigm has compelled us to critically re-examine the cytokine-driven immune events in the pathogenesis and treatment of autoimmunity. T-helper 17 cells and Regulatory T cells are two lymphocyte subsets with opposing action. In this review, we discuss the mechanism that promotes development of these cells from common precursors and specific factors that impact their cell numbers and function. Also presented are findings that suggest how the equilibrium between pre-inflammatory T helper and regulatory T-cell subsets might be pharmacologically restored for therapeutic benefit, emphasising type-1 diabetes and rheumatoid arthritis. Furthermore, the emerging clinical data showing anti-IL-17 and anti-IL-23 treatments for their efficacy in treating immune-mediated inflammatory diseases are presented.

Induction of autoimmune gastritis by neonatal thymectomy requires autoantibodies and is prevented by anti-FcγR antibodies

The autoantibodies (auto-Abs) that are a hallmark of neonatally thymectomized (NTx) mice with autoimmune gastritis (AIG) have been poorly explored. We investigated their immune significance using B cell-deficient (B(-)) mice and found that B(-) mice are totally resistant to AIG but become susceptible to AIG after receiving bone marrow cells from B(+) mice. This susceptibility is most likely caused by the production of auto-Abs by B cells because B(-) pups also became susceptible to AIG when nourished by an AIG dam producing auto-Abs of the IgG class during the suckling period. NTx B(-) mice receiving purified IgG auto-Abs at this developmental stage similarly developed AIG. Auto-Abs probably act on antigen handling for antigen presentation because the treatment of NTx B(+) mice with anti-FcγR Abs prevented the development of AIG. Auto-Abs are indispensable for AIG development but are not sufficient because auto-Ab treatment did not increase AIG incidence in NTx B(+) mice above the baseline.

Maternal compared with paternal donor kidneys are associated with poorer graft outcomes after kidney transplantation

Noninherited maternal human leukocyte antigens may be less detrimental on allograft outcomes after kidney transplantation compared with noninherited paternal antigens, but this association in the era of modern immunosuppression remains unknown. Here we determine the association between parental donor kidneys, acute rejection, and graft failure in primary live-donor parental kidney transplant recipients using data from the Australia and New Zealand Dialysis and Transplant Registry between 1997 and 2012. Of the 1139 recipients followed for a median of 7.2 years (8588 person-years), 652 received kidneys from maternal donors. Compared with paternal donor kidneys, maternal donor kidneys were associated with a significantly increased risk of acute rejection (adjusted odds ratio 1.54; 95% confidence interval [CI], 1.14-2.07) and significant overall graft loss. The latter was confined to recipients who have experienced acute rejection (adjusted hazard ratio 1.60; 95%CI, 1.05-2.43) but not in those who did not experience acute rejection. Thus, our study suggests that recipients of maternal donor kidneys have a greater risk of rejection and graft loss. Hence, clinicians and patients should be cognizant of this association when determining which of the 2 parental donors is most suitable for transplantation.

Langerhans Cells Maintain Local Tissue Tolerance in a Model of Systemic Autoimmune Disease

Systemic autoimmune diseases such as lupus affect multiple organs, usually in a diverse fashion where only certain organs are affected in individual patients. It is unclear whether the "local" immune cells play a role in regulating tissue specificity in relation to disease heterogeneity in systemic autoimmune diseases. In this study, we used skin as a model to determine the role of tissue-resident dendritic cells (DCs) in local and systemic involvement within a systemic lupus disease model. Skin-resident DCs, namely, Langerhans cells (LCs), have been implicated in regulating tolerance or autoimmunity using elegant transgenic models, however, their role in local versus systemic immune regulation is unknown. We demonstrate that although lymphocytes from skin-draining lymph nodes of autoimmune-prone MRL/MpJ-Fas(lpr/lp) (r) (MRL-lpr) mice react spontaneously to a physiological skin self-Ag desmoglein-3, epicutaneous applications of desmoglein-3 induced tolerance that is dependent on LCs. Inducible ablation of LCs in adult preclinical MRL-lpr and MRL/MpJ-Fas(+/+) mice resulted in increased autoantibodies against skin Ags and markedly accelerated lupus dermatitis with increased local macrophage infiltration, but had no effect on systemic autoantibodies such as anti-dsDNA Abs or disease in other organs such as kidneys, lung, and liver. Furthermore, skin-draining lymph nodes of LC-ablated MRL-lpr mice had significantly fewer CD4(+) T cells producing anti-inflammatory cytokine IL-10 than LC-intact controls. These results indicate that a skin-resident DC population regulates local tolerance in systemic lupus and emphasize the importance of the local immune milieu in preventing tissue-specific autoimmunity, yet have no effect on systemic autoimmunity.

Functional deficits of pertussis-specific CD4+ T cells in infants compared to adults following DTaP vaccination

Understanding the immune responses that explain why infants require multiple doses of pertussis vaccine to achieve protection against infection is a high priority. The objective of this study was to compare the function and phenotypes of antigen-specific CD4(+) T cells in adults (n=12), compared to infants (n=20), following vaccination with acellular pertussis (DTaP) vaccine. Peripheral blood mononuclear cells (PBMCs) were stimulated with pertussis toxoid (PT), pertactin (PRN) and filamentous haemagglutinin (FHA). Multi-parameter flow cytometry was used to delineate CD4(+) T cell populations and phenotypes producing interferon (IFN)-γ, interleukin (IL)-2, tumour necrosis factor (TNF)-α and IL-4. Based on surface CD69 expression, infants demonstrated activation of vaccine antigen-specific CD4(+) T cells similar to adults. However, among infants, Boolean combinations of gates suggested that type 1 (Th-1) CD4(+) T cell responses were confined largely to TNF-α(+) IL-2(+) IFN-γ(-) or TNF-α(+) IL-2(-) IFN-γ(-) . A significantly lower percentage of polyfunctional T helper type 1 (Th1) responses (TNF-α(+) IFN-γ(+) IL-2(+) ) and type 2 (Th2) responses (IL-4) were present in the infants compared to adults. Moreover, a significantly higher percentage of infants' functional CD4(+) T cells were restricted to CD45RA(-) CCR7(+) CD27(+) phenotype, consistent with early-stage differentiated pertussis-specific memory CD4(+) T cells. We show for the first time that DTaP vaccination-induced CD4(+) T cells in infants are functionally and phenotypically dissimilar from those of adults.

Sercarzian immunology--In memoriam. Eli E. Sercarz, 1934-2009

During his long career as a principal investigator and educator, Eli Sercarz trained over 100 scientists. He is best known for developing hen egg white lysozyme (HEL) as a model antigen for immunologic studies. Working in his model system Eli furthered our understanding of antigen processing and immunologic tolerance. His work established important concepts of how the immune system recognizes antigenic determinants processed from whole protein antigens; specifically he developed the concepts of immunodominance and crypticity. Later in his career he focused more on autoimmunity using a variety of established animal models to develop theories on how T cells can circumvent tolerance induction and how an autoreactive immune response can evolve over time. His theory of "determinant spreading" is one of the cornerstones of our modern understanding of autoimmunity. This review covers Eli's entire scientific career outlining his many seminal discoveries.

Cytokines in autoimmunity: role in induction, regulation, and treatment

Cytokines play a pivotal role in the pathogenesis of autoimmune diseases. The precise triggers for the breakdown of self-tolerance and the subsequent events leading to the induction of pathogenic autoimmune responses remain to be defined for most of the naturally occurring autoimmune diseases. Studies conducted in experimental models of human autoimmune diseases and observations in patients have revealed a general scheme in which proinflammatory cytokines contribute to the initiation and propagation of autoimmune inflammation, whereas anti-inflammatory cytokines facilitate the regression of inflammation and recovery from acute phase of the disease. This idea is embodied in the T helper (Th) 1/Th2 paradigm, which over the past two decades has had a major influence on our thinking about the role of cytokines in autoimmunity. Interestingly, over the past decade, the interleukin (IL)-17/IL-23 axis has rapidly emerged as the new paradigm that has compelled us to critically re-examine the cytokine-driven immune events in the pathogenesis and treatment of autoimmunity. In this 2-volume special issue of the journal, leading experts have presented their research findings and viewpoints on the role of cytokines in the context of specific autoimmune diseases.

Invariant NKT cells inhibit autoreactive B cells in a contact- and CD1d-dependent manner

Autoantibody production is a hallmark of autoimmune diseases, such as lupus and rheumatoid arthritis. Accumulating evidence suggests a role of invariant NKT (iNKT) cells in their pathogenesis. Mechanisms underlying the role of iNKT cells in these diseases, however, remain unclear. In this study, we show that iNKT cells suppress IgG anti-DNA Ab and rheumatoid factor production and reduce IL-10-secreting B cells in a contact-dependent manner, but increase total IgG production and enhance activation markers on B cells via soluble factors. In vivo reconstitution with iNKT cells also reduces autoantibody production in iNKT-deficient mice and in SCID mice implanted with B cells. Using an anti-DNA transgenic model, we found that autoreactive B cells spontaneously produce IL-10 and are activated in vivo. In the presence of activated iNKT cells, these autoreactive B cells are selectively reduced, whereas nonautoreactive B cells are markedly activated. Because iNKTs recognize CD1d, we reasoned that CD1d might play a role in the differential regulation of autoreactive versus nonautoreactive B cells by iNKT cells. Indeed, autoreactive B cells express more CD1d than nonautoreactive B cells, and CD1d deficiency in lupus mice exacerbates autoantibody production and enhances Ab response to a self-peptide but not to a foreign peptide. Importantly, iNKT cells fail to inhibit autoantibody production by CD1d-deficient B cells. Thus, iNKT cells inhibit autoreactive B cells in a contact- and CD1d-dependent manner but activate nonautoreactive B cells via cytokines. Such ability of iNKTs to suppress autoantibody production, without causing global suppression of B cells, has important implications for the development of iNKT-based therapy for autoimmune diseases.

Immunobiology of herpes simplex virus and cytomegalovirus infections of the fetus and newborn

Immunologic "immaturity" is often blamed for the increased susceptibility of newborn humans to infection, but the precise mechanisms and details of immunologic development remain somewhat obscure. Herpes simplex virus (HSV) and cytomegalovirus (CMV) are two of the more common severe infectious agents of the fetal and newborn periods. HSV infection in the newborn most commonly occurs after exposure to the virus during delivery, and can lead to a spectrum of clinical disease ranging from isolated skin-eye-mucous membrane infection to severe disseminated multiorgan disease, often including encephalitis. In contrast to HSV, clinically severe CMV infections early in life are usually acquired during the intrauterine period. These infections can result in a range of clinical disease, including hearing loss and neurodevelopmental delay. However, term newborns infected with CMV after delivery are generally asymptomatic, and older children and adults often acquire infection with HSV or CMV with either no or mild clinical symptoms. The reasons for these widely variable clinical presentations are not completely understood, but likely relate to developmental differences in immune responses.This review summarizes recent human and animal studies of the immunologic response of the fetus and newborn to these two infections, in comparison to the responses of older children and adults. The immunologic defense of the newborn against each virus is considered under the broader categories of (i) the placental barrier to infection, (ii) skin and mucosal barriers (including antimicrobial peptides), (iii) innate responses, (iv) humoral responses, and (v) cellular responses. A specific focus is made on recent studies of innate and cellular immunity to HSV and CMV.

Neonatal tolerance under breastfeeding influence: the presence of allergen and transforming growth factor-beta in breast milk protects the progeny from allergic asthma

Once the umbilical cord has been cut, immunologists have often looked at the neonate as an entity that develops on its own. For years, breast milk was considered mainly as a source of nutrients for the developing child. The extensive observations that breastfeeding affords protection toward infectious diseases and could reduce by more than the half the mortality rate because of common infections have added another key role to breastfeeding. This protection relies in great part on the passive transfer through breast milk of high amounts of microbe-specific immunoglobulins that compensate for the deficiency of immunoglobulins synthesis during the first year of life. Here, we will present and discuss our data showing how breast milk can actively shape the immune response of the progeny, particularly in the context of allergic disease. Indeed, our data obtained in a mouse model suggest that the protection attributed to breastfeeding toward asthma development might rely on immune tolerance induction. For this to occur, the mother mice needed to be exposed to the allergen by aerosol or oral route during the lactation period, which resulted into the transfer of the allergen to breast milk. The presence of the allergen together with transforming growth factor-beta in breast milk was necessary and sufficient to induce the development of regulatory T lymphocytes in the progeny and their protection from asthma development. If confirmed in human beings, this study may suggest new strategies for asthma prevention such as deliberate exposure of mother to allergens during breastfeeding and qualitative modification of artificial milks.

Neonatal immunity: faulty T-helpers and the shortcomings of dendritic cells

Immunity in the newborn is characterized by minimal T helper (Th)1 function but an excess of Th2 activity. Since Th1 lymphocytes are important to counter microbes and Th2 cells favor allergies, the newborn faces susceptibility to microbial infections and allergic reactions. Delayed maturation of certain dendritic cells leads to limited interleukin (IL)-12 production during the neonatal period. The Th2 cytokine locus of neonatal CD4(+) T cells is poised epigenetically for rapid and robust production of IL-4 and IL-13. Together, these circumstances lead to efficient differentiation of Th2 cells and the expression of an IL-4Ralpha/IL-13Ralpha1 heteroreceptor on Th1 cells. Upon re-challenge, Th2 cells rapidly produce IL-4 which utilizes the heteroreceptor to drive apoptosis of Th1 cells, thus yielding the Th2 bias of neonatal immunity.

Immunogenicity of aggregates of recombinant human growth hormone in mouse models

Aggregation of recombinant therapeutic protein products is a concern due to their potential to induce immune responses. We examined the immunogenicity of protein aggregates in commercial formulations of recombinant human growth hormone produced by freeze-thawing or agitation, two stresses commonly encountered during manufacturing, shipping and handling of therapeutic protein products. In addition, we subjected each preparation to high-pressure treatment to reduce the size and concentration of aggregates present in the samples. Aggregates existing in a commercial formulation, as well as aggregates induced by freeze-thawing and agitation stresses enhanced immunogenicity in one or more mouse models. The use of high-pressure treatment to reduce size and concentrations of aggregates within recombinant human growth hormone formulations reduced their overall immunogenicity in agreement with the "immunon" hypothesis.

The effects of formula feeding on physiological and immunological parameters in the gut of neonatal rats

A unique model of formula feeding in the neonatal rat was utilized to investigate the effects of an enterally delivered artificial milk formula on clinically relevant immunological and biological characteristics in the gut, compared to naturally reared pups. Hooded Wistar rat pups were randomly allocated to two treatment groups: formula-fed (FF) or naturally suckled (NS). A flexible silastic intra-gastric cannula was surgically implanted into the FF pups, through which an artificial rat milk supplement was continuously delivered from day 4 to day 10 of life. Rat pups were sacrificed at 10 days of age. Body weight, small intestinal weight, mucosal CD8(+) cell numbers, and ileal lactase activity in FF animals were significantly decreased compared to their NS counterparts (P < 0.05). Numbers of eosinophils, mucosal mast cells, CD4(+) T-cells, ileal villus height and gastric emptying times were significantly increased in FF pups (P < 0.05). We have developed a new rat model of artificial feeding which possesses important immunological and biological similarities to the premature human infant.

An evolutionary perspective on the mechanisms of immunosenescence

There is an accumulating body of evidence that a decline in immune function with age is common to most if not all vertebrates. For instance, age-associated thymic involution seems to occur in all species that possess a thymus, indicating that this process is evolutionary ancient and conserved. The precise mechanisms regulating immunosenescence remain to be resolved, but much of what we do know is consistent with modern evolutionary theory. In this review, we assess our current knowledge from an evolutionary perspective on the occurrence of immunosenescence, we show that life history trade-offs play a key role and we highlight the possible advantages of the age-related decline in thymic function.

Delayed maturation of an IL-12-producing dendritic cell subset explains the early Th2 bias in neonatal immunity

Primary neonatal T cell responses comprise both T helper (Th) cell subsets, but Th1 cells express high levels of interleukin 13 receptor α1 (IL-13Rα1), which heterodimerizes with IL-4Rα. During secondary antigen challenge, Th2-produced IL-4 triggers the apoptosis of Th1 cells via IL-4Rα/IL-13Rα1, thus explaining the Th2 bias in neonates. We show that neonates acquire the ability to overcome the Th2 bias and generate Th1 responses starting 6 d after birth. This transition was caused by the developmental maturation of CD8α⁺CD4⁻ dendritic cells (DCs), which were minimal in number during the first few days of birth and produced low levels of IL-12. This lack of IL-12 sustained the expression of IL-13Rα1 on Th1 cells. By day 6 after birth, however, a significant number of CD8α⁺CD4⁻ DCs accumulated in the spleen and produced IL-12, which triggered the down-regulation of IL-13Rα1 expression on Th1 cells, thus protecting them against IL-4–driven apoptosis.

Dual roles of immunoregulatory cytokine TGF-beta in the pathogenesis of autoimmunity-mediated organ damage

Ample evidence suggests a role of TGF-beta in preventing autoimmunity. Multiorgan inflammatory disease, spontaneous activation of self-reactive T cells, and autoantibody production are hallmarks of autoimmune diseases, such as lupus. These features are reminiscent of the immunopathology manifest in TGF-beta1-deficient mice. In this study, we show that lupus-prone (New Zealand Black and White)F(1) mice have reduced expression of TGF-beta1 in lymphoid tissues, and TGF-beta1 or TGF-beta1-producing T cells suppress autoantibody production. In contrast, the expression of TGF-beta1 protein and mRNA and TGF-beta signaling proteins (TGF-beta receptor type II and phosphorylated SMAD3) increases in the target organs, i.e., kidneys, of these mice as they age and develop progressive organ damage. In fact, the levels of TGF-beta1 in kidney tissue and urine correlate with the extent of chronic lesions that represent local tissue fibrosis. In vivo TGF-beta blockade by treatment of these mice with an anti-TGF-beta Ab selectively inhibits chronic fibrotic lesions without affecting autoantibody production and the inflammatory component of tissue injury. Thus, TGF-beta plays a dual, seemingly paradoxical, role in the development of organ damage in multiorgan autoimmune diseases. According to our working model, reduced TGF-beta in immune cells predisposes to immune dysregulation and autoantibody production, which causes tissue inflammation that triggers the production of anti-inflammatory cytokines such as TGF-beta in target organs to counter inflammation. Enhanced TGF-beta in target organs, in turn, can lead to dysregulated tissue repair, progressive fibrogenesis, and eventual end-organ damage.

Effector role of neonatal hepatic CD8+ lymphocytes in epithelial injury and autoimmunity in experimental biliary atresia

BACKGROUND & AIMS

Lymphocytes populate the livers of infants with biliary atresia, but it is unknown whether neonatal lymphocytes regulate pathogenesis of disease. Here, we investigate this question by examining the role of T lymphocytes in the destruction of extrahepatic bile ducts of neonatal mice using an experimental model of biliary atresia.

METHODS

Inoculation of neonatal mice with rhesus rotavirus followed by multistaining flow cytometry to quantify expression of interferon-gamma by hepatic lymphocytes, and real-time polymerase chain reaction for mRNA expression of pro-inflammatory cytokines. This was followed by determining the consequences of antibody-mediated depletion of lymphocyte subtypes on the development of biliary obstruction, and coculture and cell transfer experiments to investigate the effector role of lymphocyte subtypes on neonatal biliary disease.

RESULTS

Rotavirus infection results in overexpression of interferon-gamma by neonatal hepatic T cells. Among these cells, depletion of CD4(+) cells did not change the course of inflammatory injury and obstruction of neonatal bile ducts. In contrast, loss of CD8(+) cells remarkably suppressed duct injury, prevented luminal obstruction, and restored bile flow. Coculture experiments showed that rotavirus-primed, but not naïve, CD8(+) cells were cytotoxic to cholangiocytes. In adoptive transfer experiments, we found that primed CD8(+) cells preferentially homed to extrahepatic bile ducts of neonatal mice and invaded their epithelial lining.

CONCLUSIONS

Primed neonatal CD8(+) cells can activate a pro-inflammatory program, target diseased and healthy duct epithelium, and drive the phenotypic expression of biliary atresia, thus constituting a potential therapeutic target to halt disease progression.

Examining the role of CD1d and natural killer T cells in the development of nephritis in a genetically susceptible lupus model

OBJECTIVE

CD1d-reactive invariant natural killer T (iNKT) cells secrete multiple cytokines upon T cell receptor (TCR) engagement and modulate many immune-mediated conditions. The purpose of this study was to examine the role of these cells in the development of autoimmune disease in genetically lupus-prone (NZBxNZW)F1 (BWF1) mice.

METHODS

The CD1d1-null genotype was crossed onto the NZB and NZW backgrounds to establish CD1d1-knockout (CD1d0) BWF1 mice. CD1d0 mice and their wild-type littermates were monitored for the development of nephritis and assessed for cytokine responses to CD1d-restricted glycolipid alpha-galactosylceramide (alphaGalCer), anti-CD3 antibody, and concanavalin A (Con A). Thymus and spleen cells were stained with CD1d tetramers that had been loaded with alphaGalCer or its analog PBS-57 to detect iNKT cells, and the cells were compared between BWF1 mice and class II major histocompatibility complex-matched nonautoimmune strains, including BALB/c, (BALB/cxNZW)F1 (CWF1), and NZW.

RESULTS

CD1d0 BWF1 mice had more severe nephritis than did their wild-type littermates. Although iNKT cells and iNKT cell responses were absent in CD1d0 BWF1 mice, the CD1d0 mice continued to have significant numbers of interferon-gamma-producing NKT-like (CD1d-independent TCRbeta+,NK1.1+ and/or DX5+) cells. CD1d deficiency also influenced cytokine responses by conventional T cells: upon in vitro stimulation of splenocytes with Con A or anti-CD3, type 2 cytokine levels were reduced, whereas type 1 cytokine levels were increased or unchanged in CD1d0 mice as compared with their wild-type littermates. Additionally, numbers of thymic iNKT cells were lower in young wild-type BWF1 mice than in nonautoimmune strains.

CONCLUSION

Germline deletion of CD1d exacerbates lupus in BWF1 mice. This finding, together with reduced thymic iNKT cells in young BWF1 mice as compared with nonautoimmune strains, implies a regulatory role of CD1d and iNKT cells during the development of lupus.

Neonatal induction of myelin-specific Th1/Th17 immunity does not result in experimental autoimmune encephalomyelitis and can protect against the disease in adulthood

The neonatal immune system is believed to be biased towards T helper type 2 (Th2) immunity, but under certain conditions neonates can also develop Th1 immune responses. Neonatal Th2 immunity to myelin antigens is not pathogenic and can prevent induction of experimental autoimmune encephalomyelitis (EAE) in adulthood, but the consequences of neonatally induced Th1 immunity to self-antigens have remained unresolved. Here, we show that neonatal injection of mice with myelin antigens emulsified in complete Freund's adjuvant (CFA) induced vigorous production of IFN-gamma and IL-17, but not IL-5, consistent with myelin-specific Th1/Th17 immunity. Importantly, the myelin-specific Th1/Th17 cells persisted in the mice until adulthood without causing symptoms of EAE. Intraperitoneal, but not subcutaneous injection of neonates with myelin antigens protected against induction of EAE as adults. Intraperitoneally injected neonates showed a substantial decrease of the number and avidity of myelin-reactive Th17 cells, suggesting a decrease in IL-17 producing precursor cells as the mechanism of protection from EAE upon re-injection with myelin antigens as adults. The results could provide a rationale for the presence of autoreactive T cells found in healthy human individuals without autoimmune disease.

Immunoregulatory role of Jalpha281 T cells in aged mice developing lupus-like nephritis

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the emergence of autoreactive T cells. Humans and mice with SLE have reduced numbers of CD1d-restricted invariant natural killer T (iNKT) cells, suggesting a key role for these cells in its immunopathogenesis. This subset uses an invariant TCR constituted by Valpha14 Jalpha281 chains paired with some Vbeta domains. The regulatory role for iNKT cells in non-autoimmune mice was suggested by our previous results showing that aged Jalpha281 knockout (KO) mice produce anti-dsDNA. Here we show that old Jalpha281 KO mice have proteinuria and antibodies against dsDNA and cardiolipin. Histological analysis of Jalpha281 KO mice revealed glomeruli damage and deposition of C3c and IgG, mainly of the IgG3 subclass. In spleens of aged Jalpha281 KO mice there is an increase of activated marginal zone B cells. The evolution of lesions may depend on the age-associated increase of autoantibodies production, preferentially IgG3, mainly secreted by marginal zone B cells. Our results provide the first evidence of a lupus-like syndrome in non-autoimmune mice, supporting an age-related immunoregulatory role of Jalpha281+ cells, probably associated with the activation of marginal zone B cells.

Early exposure to a nonhygienic environment alters pulmonary immunity and allergic responses

The hygiene hypothesis suggests that early life exposure to a nonhygienic environment that contains endotoxin reduces the risk of developing allergic diseases. The mechanisms underlying the hygiene hypothesis are unclear and may involve subtle immune system interactions that occur during maturation. Experimental objectives of this study were to use a novel animal model to test the hygiene hypothesis and to characterize early life immune system responses to a nonhygienic environment. Mice were reared in corn dust, a grain-processing byproduct with a high-endotoxin content and microbial products or in a low-endotoxin environment. The influence of early or later life exposure to corn dust on a subsequent allergen stimulus (ovalbumin) was assessed by bronchoalveolar lavage (BAL) cell analysis, lung histology, serum IgE, and BAL cytokine measurements. The influence of the corn dust environment on the developing pulmonary immune system was assessed by BAL cell analysis and immunostaining of lung tissue. The corn dust environment contained significantly more endotoxin ( P < 0.001), and the dust exposures attenuated the cellular inflammatory response to ovalbumin in the adult mouse ( P < 0.01) but did not reduce serum IgE levels or alter baseline BAL fluid proinflammatory cytokine levels. The corn dust environment did not induce significant neutrophilia in lavage fluid but significantly increased the number of antigen-presenting cells in alveolar walls early in life by ∼37%. In conclusion, exposure to a nonhygienic environment did not induce significant airway neutrophilia, yet altered the population of immunologically active cells in the lung and reduced subsequent allergic inflammation.

The key regulators of adult T helper cell responses, STAT6 and T-bet, are established in early life in mice

Murine neonatal immunity is typically Th2 biased. This is characterized by high-level IL-4 production at all phases of the immune response and poor IFN-gamma memory responses. The differential expression of Th1/Th2 cytokines by neonates and adults could arise if the critical regulators of Th differentiation and function, STAT6 and T-bet, operate differently during the neonatal period. To test this idea, the Th cell responses of wild-type, T-bet-deficient, or STAT6-deficient mice were compared in vitro and in vivo. The absence of these factors had similar qualitative effects on the development of effector function in neonates and adults, i.e., if a Th lineage was inhibited or enhanced in adult animals, a similar phenomenon was observed in neonates. However, there was a striking difference observed in the in vivo Th1 memory responses of STAT6-deficient mice initially immunized as neonates. Antigen-specific IFN-gamma production was increased 50-100-fold in STAT6-deficient neonates, achieving levels similar to those of STAT6-deficient adults. These findings demonstrate that STAT6 and T-bet signals are central in shaping Th responses in wild-type neonates, as in adult mice, and that the master regulators of Th cell development and function are already firmly established in early life.

neonatally primed lymph node, but not splenic T cells, display a Gly-Gly motif within the TCR beta-chain complementarity-determining region 3 that controls affinity and may affect lymphoid organ retention

Ig-proteolipid protein 1 (Ig-PLP1) is an Ig chimera expressing the encephalitogenic PLP1 peptide corresponding to amino acid residues 139-151 of PLP. Newborn mice given Ig-PLP1 in saline on the day of birth and challenged 7 wk later with PLP1 peptide in CFA develop an organ-specific neonatal immunity that confers resistance against experimental allergic encephalomyelitis. The T cell responses in these animals are comprised of Th2 cells in the lymph node and anergic Th1 lymphocytes in the spleen. Intriguingly, the anergic splenic T cells, although nonproliferative and unable to produce IFN-gamma or IL-4, secrete significant amounts of IL-2. Studies were performed to determine whether the two populations display any structural differences in the TCR H chain variable region that could contribute to the differential affinity and retention in different organs. Responsive Th2 lymph node T cells and anergic splenic lymphocytes were immortalized, and the structures of their TCR Vbeta were determined. The results show that Vbeta and Jbeta usage was random, but the CDR3 regions of the lymph node cells had a conserved Gly-Gly motif. Analysis of TCR affinity/avidity correlated the Gly-Gly motif with lower affinity and retention of the Th2 cells in the lymph node. Also, it is suggested that a higher TCR affinity may be a contributing factor for the development of the neonatal Th1 response in the spleen.

Autoimmune ovarian disease in day 3-thymectomized mice: the neonatal time window, antigen specificity of disease suppression, and genetic control

Discovery of the CD4+CD25+ T cells has stemmed from investigation of the AOD in the d3tx mice. Besides CD4+CD25+ T cell depletion, d3tx disease induction requires effector T cell activation prompted by lymphopenia. This is supported by other neonatal AOD models in which T cell-mediated injury has been found to be triggered by immune complex or Ag immunization. In addition, there is growing evidence that support a state of neonatal propensity to autoimmunity, which depends on concomitant endogenous antigenic stimulation, concomitant nematode infection, resistance to CD4+CD25+ T cell regulation, and participation of the neonatal innate system. The suppression of d3tx disease by polyclonal CD4+CD25+ T cells appears to be dependent on endogenous Ag and the persistence of regulatory T cells. Thus, suppression of AOD occurs in the ovarian LN, and AOD emerges upon ablation of the input regulatory T cells; and in AIP, the hormone-induced expression of prostate Ag in the CD4+CD25+ T cell donors rapidly enhances the capacity to suppress disease over Ag negative donors. Finally, genetic analysis of AOD and its component phenotypes has uncovered seven Aod loci. As the general themes that emerged, significant epistatic interactions among the loci play a role in controlling disease susceptibility, the majority of the Aod loci are linked to susceptibility loci of other autoimmune diseases, and the genetic intervals encompass candidate genes that are differentially expressed between CD4+CD25+ T cells and other T cells. The candidate genes include Pdcd1, TNFR superfamily genes, H2, Il2, Tgfb, Nalp5 or Mater, an oocyte autoAg that reacts with autoantibody in sera of d3tx mice.

Neonatal autoimmune disease: influence of CD4+ CD25+ regulatory T cells

Although previous studies have emphasized the tolerogenic property of murine neonatal immune system, recent studies indicate that neonatal mice are prone to autoimmune disease. This chapter will summarize the evidence for neonatal propensity to autoimmune ovarian disease (AOD) and describe the new finding that autoantibody can trigger a T cell-dependent autoimmune disease in neonatal but not adult mice. Based on depletion or addition of the CD4+ CD25+ T cells, disease resistance of older mice is explicable by the emergence of CD4+ CD25+ regulatory T-cell function after day 5, whereas disease susceptibility is associated with resistance to regulation by CD4+ CD25+ T cells.

CD226 expression deficiency causes high sensitivity to apoptosis in NK T cells from patients with systemic lupus erythematosus

Humans and mice with systemic lupus erythematosus (SLE) and related autoimmune diseases have reduced numbers of NK T cells. An association between NK T cell deficiency and autoimmune disease has been identified. However, the mechanisms for reduction of NK T cell number in patients with SLE are unknown. In the present study we report that NK T cells from active SLE patients are highly sensitive to anti-CD95-induced apoptosis compared with those from normal subjects and inactive SLE patients. CD226 expression is deficient on NK T cells from active SLE patients. The expression of one antiapoptotic member protein, survivin, is found to be selectively deficient in freshly isolated NK T cells from active SLE patients. CD226 preactivation significantly up-regulates survivin expression and activation, which can rescue active SLE NK T cells from anti-CD95-induced apoptosis. In transfected COS7 cells, we confirm that anti-CD95-mediated death signals are inhibited by activation of the CD226 pathway through stabilization of caspase-8 and caspase-3 and through activation of survivin. We therefore conclude that deficient expression of CD226 and survivin in NK T cells from active SLE is a molecular base of high sensitivity of the cells to anti-CD95-induced apoptosis. These observations offer a potential explanation for high apoptotic sensitivity of NK T cells from active SLE, and provide a new insight into the mechanism of reduction of NK T cell number in SLE and understanding the association between NK T cell deficiency and autoimmune diseases.

Adoptive transfer of dendritic cells modulates immunogenesis and tolerogenesis in a neonatal model of murine cutaneous leishmaniasis

We evaluated the adoptive transfer of DCs on Leishmania (L.) mexicana-infected neonatal BALB/c mice. DCs were isolated and purified from the spleens of the following donor groups: a) Adult BALB/c mice infected during adulthood with L. (L) mexicana; b) Adult BALB/c mice infected during neonatal life; c) Healthy neonatal BALB/c mice; d) Healthy adult BALB/c mice. A neonatal model of infection, generated after inoculation with 5 × 105 promastigotes of L. (L) mexicana, was used as the infection control group. Sixteen hours after intraperitoneal transfer of DCs (1 × 103, 1 × 105, or 1 × 106 cells/ml), neonatal recipient BALB/c mice were infected. The adoptive transfer of DCs diminished disease progression in neonatal mice. This reduction depends on the quantity and provenance of transferred DCs, since the effect was more evident with high numbers of DCs from adult mice infected during adulthood and healthy neonatal mice. Protection was significantly reduced in animals receiving DCs from healthy adult mice but it was absent in mice receiving DCs from adult mice infected during neonatal life. These results suggest that genetic susceptibility to Leishmania infection can be modified during neonatal life, and that the period of life when antigens are encountered is crucial in influencing the capacity of DCs to induce resistance or tolerance.

An ACE inhibitor reduces Th2 cytokines and TGF-beta1 and TGF-beta2 isoforms in murine lupus nephritis

BACKGROUND

Angiotensin-converting enzyme (ACE) inhibitors, such as captopril, are used to control hypertension. In patients and animals with primary nephropathies, these agents improve renal function more than that would be expected from their control of hypertension. Here, we examine the effects of treatment with captopril on lupus nephritis and discuss the potential mechanism(s) by which this agent exerts its renoprotective effects.

METHODS

Lupus-prone, NZB/NZW F1 and MRL-lpr/lpr, mice were treated with captopril or with a control antihypertensive agent, verapamil. Mice were monitored for nephritis, and their sera and tissues analyzed for cytokine and transforming growth factor-beta (TGF-beta) expression.

RESULTS

Captopril treatment delayed the onset of proteinuria when administered to prenephritic mice, whereas verapamil did not. Captopril treatment also retarded disease progression when given to lupus mice that had early disease, and even reversed severe proteinuria in at least some older animals with advanced disease. It reduced chronic renal lesions, but had no effect on autoantibody production. The improvement in renal disease correlated with reduced TGF-beta expression, particularly of the TGF-beta1 and TGF-beta2 isoforms, in the kidneys. Interestingly, in vivo or in vitro exposure to captopril reduced splenic levels of type 2 cytokines, interleukin (IL)-4 and IL-10, suggesting a possible role of the immune system in captopril-mediated disease modulation.

CONCLUSION

Since type 2 cytokines are known to promote lupus glomerulosclerosis, decreased IL-4 and IL-10 production in captopril-treated mice may be related to this agent's renoprotective effects. We argue here that ACE inhibitors not only act as selective TGF-beta inhibitors, but also as selective immunomodulators, to improve lupus nephritis.

CD1d deficiency exacerbates inflammatory dermatitis in MRL-lpr/lpr mice

Mechanisms responsible for the development of autoimmune skin disease in humans and animal models with lupus remain poorly understood. In this study, we have investigated the role of CD1d, an antigen-presenting molecule known to activate natural killer T cells, in the development of inflammatory dermatitis in lupus-susceptible MRL-lpr/lpr mice. In particular, we have established MRL-lpr/lpr mice carrying a germ-line deletion of the CD1d genes. We demonstrate that CD1d-deficient MRL-lpr/lpr mice, as compared with wild-type littermates, have more frequent and more severe skin disease, with increased local infiltration with mast cells, lymphocytes and dendritic cells, including Langerhans cells. CD1d-deficient MRL-lpr/lpr mice had increased prevalence of CD4(+) T cells in the spleen and liver and of TCR alpha beta (+)B220(+) cells in lymph nodes. Furthermore, CD1d deficiency was associated with decreased T cell production of type 2 cytokines and increased or unchanged type 1 cytokines. These findings indicate a regulatory role of CD1d in inflammatory dermatitis. Understanding the mechanisms by which CD1d deficiency results in splenic T cell expansion and cytokine alterations, with increased dermal infiltration of dendritic cells and lymphocytes in MRL-lpr/lpr mice, will have implications for the pathogenesis of inflammatory skin diseases.

Adjuvant costimulation during secondary antigen challenge directs qualitative aspects of oral tolerance induction, particularly during the neonatal period

In this report we demonstrate that although passive feeding of specific Ag to mice as neonates or adults can induce oral tolerance in both the cellular and humoral arms of the immune response, quantitative and, in particular, qualitative aspects of the tolerance process are determined by the nature of the inflammatory costimuli provided at the time of secondary Ag challenge. Moreover, this dependency upon nonspecific costimulation is more profound in Ag-fed neonates than in their adult counterparts. Thus, administration of Ag in the Th1-selective adjuvant CFA to prefed animals resulted in significant inhibition of IgG2a, IL-2, and IFN-gamma responses, whereas IL-5 responses were increased. In contrast, rechallenge with Ag in the Th2-selective adjuvant aluminum hydroxide resulted in significant inhibition of IgG1, IgE, IL-2, and IL-5 responses, whereas IFN-gamma responses were increased. Additionally, although soluble Ag challenge of prefed adults revealed marginal tolerogenic effects, the same challenge protocol in animals prefed as neonates elicited enhanced Th2-dependent IgG1 production. These results suggest that inflammatory stimulation at the time of Ag challenge is obligatory to trigger oral tolerance mechanisms, particularly in animals fed as neonates and also that the type of adjuvant used at the time of challenge selects for the type of Th cell population to be inhibited.

IL-4 Utilizes an Alternative Receptor to Drive Apoptosis of Th1 Cells and Skews Neonatal Immunity toward Th2

Primary neonatal Th1 cells develop alongside of Th2 upon priming of the newborn but undergo apoptosis upon recall with antigen. These Th1 cells were isolated, and their death was correlated with elevated IL-13Ralpha1 chain expression. Strikingly, neutralization of Th2s' IL-4 reduced apoptosis, sustained recall responses, and the live Th1 cells displayed a decrease in IL-13Ralpha1 expression. Blockade of IL-13Ralpha1 or IL-4Ralpha also restores recall and secondary Th1 responses. Adult T cells primed within the neonatal environment did not upregulate IL-13Ralpha1 chain or undergo apoptosis and developed recall Th1 responses. These observations indicate that developmental expression of IL-13Ralpha1 along with IL-4Ralpha provides a receptor through which IL-4 induces death of Th1 cells and skews neonatal immunity toward Th2.

Tolerance to noninherited maternal MHC antigens in mice

The phenomenon of tolerance to noninherited maternal Ags (NIMA) is poorly understood. To analyze the NIMA effect C57BL/6 (H-2(b/b)) males were mated with B6D2F(1) (H-2(b/d)) females, whereby 50% of the offspring are H-2(b/b) mice that have been exposed to maternal H-2(d) alloantigens. Controls were H-2(b/b) offspring of C57BL/6 mothers, either inbred C57BL/6 mice or F(1) backcross mice from breedings with H-2(b/d) fathers. We found that 57% of the H-2(b/b) offspring of semiallogeneic (H-2(b/d)) mothers accepted fully allogeneic DBA/2 (H-2(d/d)) heart grafts for >180 days, while similar transplants were all rejected by day 11 in controls (p < 0.0004). Foster nursing studies showed that both oral and in utero exposure to NIMA are required for this tolerogenic effect. An effect of NIMA was also found to extend the survival of skin grafts from a semiallogeneic donor (p < 0.02). Pretransplant analysis of splenocytes showed a 40-90% reduction of IL-2-, IL-5-, and IFN-gamma-producing T cells responding to H-2(d)-expressing APC in NIMA(d)-exposed vs control mice. Injection of pregnant BALB/c-dm2 (H-2L(d)-negative) female mice i.v. with H-2L(d)(61-80) peptide profoundly suppressed the offspring's indirect pathway alloreactive CD4(+) T cell response to H-2L(d). These results suggest that the natural exposure of the fetus and newborn to maternal cells and/or soluble MHC Ags suppresses NIMA-allospecific T cells of the offspring, predisposing to organ transplant tolerance in adult mice.

Oral tolerance

Autoimmune conditions caused by injurious immune responses against self-antigens can be ameliorated if the inappropriate responses to self-components that cause tissue injury can be modulated by regulatory cells or shut off via the induction of anergy or via deletion of pathogenic immune responses. Antigen encounter at the gut mucosa can lead to suppression of injurious immune responses to self-antigen via these mechanisms. This type of immunological event is termed oral tolerance. In this review, we examine the mechanisms behind the induction of oral tolerance and provide findings from its use as a form of treatment for autoimmune diseases.

Nasal instillation of gpMBP can exacerbate murine EAE: effect of mucosal priming is an age-dependent phenomenon

Nasal installation or oral feeding of antigens can alter the subsequent immune response in animals and humans. Most mucosal treatments with antigens tend to down-regulate disease, inducing full tolerance or immune deviation; however, priming has also been reported. We evaluated the course of experimental autoimmune encephalomyelitis (EAE) in (SJL x B10.PL)F1 mice after nasal instillation of myelin basic protein. There was a tendency towards exacerbation of subsequent disease in animals if they were nasally exposed to gpMBP during the neonatal period (first week of life), compared to exposure during adulthood. Later, at 11 months of age, this tendency to exacerbate disappeared. Our results suggest that mucosal exposure during early life may regularly modulate the anti-self immune response upwards in individuals genetically predisposed to autoimmune diseases.

Hepatitis B immunisation induces higher antibody and memory Th2 responses in new-borns than in adults

New-borns raise limited antibody responses to most T cell-dependent antigens but little is known about neonatal T lymphocyte responses to vaccines. In this study, we compared the immune response induced by the hepatitis B vaccine in new-borns and nai;ve adults. Infants produced markedly higher serum anti-hepatitis B surface (HBs) antibody titres than adults. This was not associated with greater HBs Ag-specific Th2 cytokine responses but with lower primary IFN-gamma responses. At 1 year, the infant memory response to HBs Ag was characterised by higher Th2 responses than those of adults. We conclude that neonatal antibody and T cell responses to hepatitis B vaccine differ from those induced in adults.

Beneficial autoimmunity to proinflammatory mediators restrains the consequences of self-destructive immunity

Therapies that neutralize the function of TNF-alpha suppress rheumatoid arthritis (RA) but not osteoarthritis (OA). We show that patients suffering from RA but not OA have significant levels of autoantibodies directed to TNF-alpha. Thus, the immune system can selectively generate autoimmunity to proinflammatory mediators when such a response is beneficial for the host. A well-defined model of RA was used to elaborate the contribution of beneficial autoimmunity to the regulation of disease. We show that during the disease autoantibody production is elicited against few inflammatory, but not regulatory, mediators. Selective amplification of these beneficial antibodies by targeted DNA vaccines provided protective immunity. Epitope mapping revealed that anti-TNF-alpha immunity is highly restricted and excretes no crossreactivity to other known gene products. Its selective exclusion substantially exacerbated the disease. Administration of anti-TNF-alpha antibodies could then override this aggravation. This substantiates the significance of beneficial autoimmunity in restraining self-destructive immunity.

Maternal milk regulation of cell infiltration and interleukin 18 in the intestine of suckling rat pups

BACKGROUND

and aims: In neonates the gastrointestinal tract is exposed to food and bacterial antigens at a time when the gut mucosal immune system has not developed the ability to induce oral tolerance. This increases the risk for an inappropriate immune response to oral antigens. Transforming growth factor beta (TGF-beta) is an immunoregulatory cytokine present in high concentration in maternal milk. Interleukin 18 (IL-18) is a cytokine that mediates early immune events, and drives T cell development. We assessed the role of TGF-beta in mediating mucosal immune development and specifically the effect on endogenous IL-18.

METHODS

Rat pups were randomly assigned to the following groups, naturally suckled, maternal milk via cannula, and formula fed with and without physiological levels of TGF-beta2. A comparison of the immune response profile was then carried out. Cytokine profiles, dendritic cell, intestinal mast cell, and eosinophil numbers were assessed.

RESULTS

We show that feeding formula deficient in TGF-beta2 resulted in accumulated IL-18 protein release from intestinal epithelial cells and IL-18 mRNA up regulation. A proinflammatory cytokine profile resulted in the gut, along with increased numbers of activated dendritic cells, eosinophils, and mast cells. Supplementation of the formula with TGF-beta2 down regulated the proinflammatory cytokine mRNA as well as the number of activated lymphocytes, eosinophils, mast cells, CD80, and CD86 positive dendritic cells.

CONCLUSION

The data suggests an important role for maternal milk, in regulating immune responses after exposure to food antigens, which might otherwise induce deleterious immune responses in the intestine of suckling neonates. This regulation is potentially mediated by milk TGF-beta2, as well as endogenous IL-18.

Repeated α-Galactosylceramide Administration Results in Expansion of NK T Cells and Alleviates Inflammatory Dermatitis in MRL-lpr/lpr Mice

NK T (NKT) cells expressing the invariant Valpha14-Jalpha18 TCR alpha-chain recognize glycolipid Ags such as alpha-galactosylceramide (alpha-GalCer) presented by the MHC class I-like molecule CD1d. Upon activation by alpha-GalCer, invariant NKT cells secrete multiple cytokines and confer protection in certain immune-mediated disorders. Here we have investigated the role of NKT cells in the development of inflammatory dermatitis in MRL-lpr/lpr mice, which shares features with lupus in humans. Our results show that the numbers Sand functions of NKT (TCRbeta(+)CD1d/alpha-GalCer tetramer(+)) cells, particularly of the NK1.1(-) subset, are reduced in MRL-lpr/lpr mice compared with MRL-fas/fas and/or nonautoimmune C3H/Hej and BALB/c mice. Repeated treatments with alpha-GalCer result in the expansion of NKT cells and alleviate dermatitis in MRL-lpr/lpr mice. Our results indicate that NKT cell deficiency can be corrected by repeated alpha-GalCer treatment and that NKT cells may play a protective role in inflammatory dermatitis of lupus-prone mice.

Immunoregulatory role of CD1d in the hydrocarbon oil-induced model of lupus nephritis

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease that is accompanied by the emergence of autoreactive T cells and a reduction in regulatory T cells. Humans and mice with SLE have reduced numbers of CD1d-restricted NK T cells, suggesting a role for these cells in the regulation of SLE. In this study, we show that CD1d deficiency exacerbates lupus nephritis induced by the hydrocarbon oil pristane. This exacerbation in disease is associated with: 1) reduced TNF-alpha and IL-4 production by T cells, especially during the disease induction phase; and 2) expansion of marginal zone B cells. Strikingly, inoculation of pristane in wild-type mice resulted in reduced numbers and/or functions of NK T cells and CD1d-expressing dendritic cells. These findings suggest that CD1d may play an immunoregulatory role in the development of lupus in the pristane-induced model.

Break of neonatal Th1 tolerance and exacerbation of experimental allergic encephalomyelitis by interference with B7 costimulation

Ig-PLP1 is an Ig chimera expressing proteolipid protein-1 (PLP1) peptide corresponding to aa residues 139-151 of PLP. Newborn mice given Ig-PLP1 in saline on the day of birth and challenged 7 wk later with PLP1 peptide in CFA develop an organ-specific neonatal immunity that confers resistance against experimental allergic encephalomyelitis. The T cell responses in these animals comprise Th2 cells in the lymph node and anergic Th1 lymphocytes in the spleen. Intriguingly, the anergic splenic T cells, although nonproliferative and unable to produce IFN-gamma or IL-4, secrete significant amounts of IL-2. In this work, studies were performed to determine whether costimulation through B7 molecules plays any role in the unusual form of splenic Th1 anergy. The results show that engagement of either B7.1 or B7.2 with anti-B7 Abs during induction of EAE in adult mice that were neonatally tolerized with Ig-PLP1 restores and exacerbates disease severity. At the cellular level, the anergic splenic T cells regain the ability to proliferate and produce IFN-gamma when stimulated with Ag in the presence of either anti-B7.1 or anti-B7.2 Ab. However, such restoration was abolished when both B7.1 and B7.2 molecules were engaged simultaneously, indicating that costimulation is necessary for reactivation. Surprisingly, both anti-B7.1 and anti-B7.2 Abs triggered splenic dendritic cells to produce IL-12, a key cytokine required for restoration of the anergic T cells. Thus, recovery from neonatally induced T cell anergy requires B7 molecules to serve double functions, namely, costimulation and induction of cytokine production by APCs.

IL-4 and many roads to lupuslike autoimmunity

Interleukin-4 (IL-4) is a multifunctional cytokine. Although most studies have focused on the B-cell stimulatory and Th2 promoting properties of IL-4 in the development of autoantibodies and autoantibody-mediated diseases, a few reports suggest a T-cell suppressor role for this cytokine in lupus. Since these properties of IL-4 may sometimes result in opposing outcomes, amplifying or inhibitory, on overall B-cell functions, it is not surprising that a few studies have found no role for IL-4 in the development of autoantibodies and lupus. Evidence for a more novel role for IL-4 in the development of lupus nephritis comes from recent studies, which suggests that IL-4 may directly promote extracellular matrix deposition in the glomeruli. Consistent with this idea, blockade of IL-4 by antibody treatment or of its signaling by inactivation of the Stat6 gene ameliorates glomerulosclerosis and delays or even prevents the development of end-stage renal disease, despite the presence of high levels of IgG anti-dsDNA Antibodies. Thus, IL-4 may serve multiple roles in the development of lupus: it may enhance autoantibody production via its direct B-cell effects, protect against autoimmunity via its T-cell suppressor effect, or perpetuate tissue damage via its direct effects on target organs.

Memory and effector T cells modulate subsequently primed immune responses to unrelated antigens

Memory and effector T cells modulate subsequently primed T cell responses to the same antigen. However, little is known about the impact of pre-existing memory and effector T cell immunity on subsequently primed immune responses to unrelated antigens. Here, we show that an antigen-primed first wave of Th1 and Th2 immunity enhanced or inhibited the subsequently primed T cell immunity to an unrelated antigen, depending on whether the second antigen was administered in the same or opposite type of adjuvant. The regulatory effects of the first wave of T cell immunity on the subsequent T cell responses to an unrelated antigen attenuated over time. Notably, following challenge with the second antigen, there was a mutual cross-regulation between the first and second wave of humoral responses to unrelated antigens. Thus, immunization with one antigen not only primes immune responses to that antigen, but also influences subsequently primed immune responses to unrelated antigens.