Immunologic and clinical studies on murine experimental autoimmune gastritis induced by neonatal thymectomy

Rat Experimental Autoimmune Gastritis Model

BACKGROUND

Autoimmune gastritis (AIG) is an autoimmune disease of the stomach characterized by the destruction of the oxyntic mucosa, which stops producing acid and becomes both functionally and morphologically atrophic. The pathogenic mechanisms behind the disease are still poorly understood. There is no early diagnosis and specific AIG therapy. To elucidate the pathogenesis of AIG, to search for early diagnostic markers, as well as to test new therapeutic approaches, an adequate and easily reproducible experimental model for autoimmune gastritis (EAG) is needed. Existing EAG models have some limitations, including slow development of signs, absence of advanced gastritis, irrational use of animals to obtain antigen. The aim was to find out whether it is possible to cause autoimmune gastritis similar to human disease in Wistar rats through immunization with a homologous gastric mucosa extract.

METHODS

Wistar rats were immunized with gastric mucosa extract. Histology studies and evaluation of serological parameters were performed 56 and 91 days later.

RESULTS

Destruction of oxyntic glands by infiltrating T lymphocytes were detected in rats on 56 and 91 days after initial immunization with gastric mucosa extract. Hyperplasia of enterochromaffin-like (ECL) cells was detected on the 91st day. Antral mucosa remained unchanged.

CONCLUSION

Wistar rats, immunized with gastric mucosa extract, developed EAG similar to human AIG. The advantages of received EAG model are the ease of obtaining, the rapid development of oxyntic mucosa damage, which may progress to ECL cell hyperplasia.

Disruption of thymic central tolerance by infection with murine roseolovirus induces autoimmune gastritis

Infections with herpesviruses, including human roseoloviruses, have been proposed to cause autoimmune disease, but defining a causal relationship and mechanism has been difficult due to the ubiquitous nature of infection and development of autoimmunity long after acute infection. Murine roseolovirus (MRV) is highly related to human roseoloviruses. Herein we show that neonatal MRV infection induced autoimmune gastritis (AIG) in adult mice in the absence of ongoing infection. MRV-induced AIG was dependent on replication during the neonatal period and was CD4+ T cell and IL-17 dependent. Moreover, neonatal MRV infection was associated with development of a wide array of autoantibodies in adult mice. Finally, neonatal MRV infection reduced medullary thymic epithelial cell numbers, thymic dendritic cell numbers, and thymic expression of AIRE and tissue-restricted antigens, in addition to increasing thymocyte apoptosis at the stage of negative selection. These findings strongly suggest that infection with a roseolovirus early in life results in disruption of central tolerance and development of autoimmune disease.

Two Distinct Etiologies of Gastric Cancer: Infection and Autoimmunity

Gastric cancer is a leading cause of mortality worldwide. The risk of developing gastric adenocarcinoma, which comprises >90% of gastric cancers, is multifactorial, but most associated with Helicobacter pylori infection. Autoimmune gastritis is a chronic autoinflammatory syndrome where self-reactive immune cells are activated by gastric epithelial cell autoantigens. This cause of gastritis is more so associated with the development of neuroendocrine tumors. However, in both autoimmune and infection-induced gastritis, high risk metaplastic lesions develop within the gastric mucosa. This warrants concern for carcinogenesis in both inflammatory settings. There are many similarities and differences in disease progression between these two etiologies of chronic gastritis. Both diseases have an increased risk of gastric adenocarcinoma development, but each have their own unique comorbidities. Autoimmune gastritis is a primary cause of pernicious anemia, whereas chronic infection typically causes gastrointestinal ulceration. Both immune responses are driven by T cells, primarily CD4⁺ T cells of the IFN-γ producing, Th1 phenotype. Neutrophilic infiltrates help clear H. pylori infection, but neutrophils are not necessarily recruited in the autoimmune setting. There have also been hypotheses that infection with H. pylori initiates autoimmune gastritis, but the literature is far from definitive with evidence of infection-independent autoimmune gastric disease. Gastric cancer incidence is increasing among young women in the United States, a population at higher risk of developing autoimmune disease, and H. pylori infection rates are falling. Therefore, a better understanding of these two chronic inflammatory diseases is needed to identify their roles in initiating gastric cancer.

Potential role of bacterial lipopolysaccharides in the development of autoimmune gastritis induced by neonatal thymectomy

The role of LPS in the development of autoimmune gastritis (AIG) in BALB/c mice thymectomized on day 3 after birth (d3-Tx) was investigated in LPS-non-responder BALB/lpsdmice. The symptoms were classified into three types: (i) hypertrophic stomach (HS) and lymphocyte infiltration (LI)-double negative; (ii) HS-negative and LI-positive; and (iii) HS- and LI-double positive. The double positive type-3 was termed AIG. Following d3-Tx, LPS-responder BALB/c ( Lpsn) mice showed the following incidence: type-1 (14%), type-2 (14%) and type-3 (72%). In contrast, the incidence in BALB/lpsdmice was 67%, 22% and 11%, respectively. Thus the frequency of AIG development in BALB/lpsdmice was much lower than in BALB/c mice. A single administration of LPS on day 2 post-d3-Tx induced severe AIG incidence in all d3-Tx BALB/c mice but not in d3-Tx BALB/lpsdmice, suggesting that LPS influences the progression of AIG development. Formation of auto-antibodies against the proton pump (H+/K+-ATPase) seemed to be related to AIG incidence in d3-Tx BALB/c mice. In d3-Tx BALB/lpsdmice, however, higher levels of auto-antibodies were detected in the type-2 mice, whereas AIG incidence was much lower than that in d3-Tx BALB/c mice. Thus, formation of auto-antibodies against the proton pump in d3-Tx BALB/lpsdmice does not appear to correlate with AIG pathogenesis.

Regulatory T Cells Control Th2-Dominant Murine Autoimmune Gastritis

Pernicious anemia and gastric carcinoma are serious sequelae of autoimmune gastritis (AIG). Our study indicates that in adult C57BL/6-DEREG mice expressing a transgenic diphtheria toxin receptor under the Foxp3 promoter, transient regulatory T cell (Treg) depletion results in long-lasting AIG associated with both H(+)K(+)ATPase and intrinsic factor autoantibody responses. Although functional Tregs emerge over time during AIG occurrence, the effector T cells rapidly become less susceptible to Treg-mediated suppression. Whereas previous studies have implicated dysregulated Th1 cell responses in AIG pathogenesis, eosinophils have been detected in gastric biopsy specimens from patients with AIG. Indeed, AIG in DEREG mice is associated with strong Th2 cell responses, including dominant IgG1 autoantibodies, elevated serum IgE, increased Th2 cytokine production, and eosinophil infiltration in the stomach-draining lymph nodes. In addition, the stomachs exhibit severe mucosal and muscular hypertrophy, parietal cell loss, mucinous epithelial cell metaplasia, and massive eosinophilic inflammation. Notably, the Th2 responses and gastritis severity are significantly ameliorated in IL-4- or eosinophil-deficient mice. Furthermore, expansion of both Th2-promoting IFN regulatory factor 4(+) programmed death ligand 2(+) dendritic cells and ILT3(+) rebounded Tregs was detected after transient Treg depletion. Collectively, these data suggest that Tregs maintain physiological tolerance to clinically relevant gastric autoantigens, and Th2 responses can be a pathogenic mechanism in AIG.

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.

Dominant trait linked to chromosome 1 in DBA/2 mice for the resistance to autoimmune gastritis appears in bone marrow cells

Neonatal thymectomy (NTx) induces autoimmune gastritis (AIG) in BALB/c mice, a model for human type A chronic atrophic gastritis, but not in DBA/2 mice and rarely in CDF1 mice (a hybrid of BALB/c and DBA/2 mice). The aim of this study was to clarify the mechanisms of AIG-resistance in mice bearing the dominant trait of DBA/2. Linkage groups associated with, and cells related to AIG resistance were examined with CDF1-BALB/c backcrosses. Intracellular staining and flow-cytometric bead array for several cytokines were performed on NTx BALB/c mice and NTx DBA/2-chimeric BALB/c mice receiving DBA/2-bone marrow cells. In NTx BALB/c mice, IFN-γ-secreting CD4(+) T cells were increased, but not in NTx DBA/2 mice. Because Vβ6(+) T cell-bearing mice of half of their backcrosses developed AIG, but the other half of Vβ6(+) T cell-negative mice developed scarcely, resistance for AIG generation is associated with the presence of the Mls-1a locus on chromosome 1 in DBA/2 mice, which deletes Vβ6(+) T cells. NTx DBA/2-chimera BALB/c mice showed dominant production of IL-10 and resistance for AIG, although the deletion of Vβ6(+) T cells was found not to be a cause of AIG-resistance from Mls-1a locus segregation experiments. Although NTx DBA/2-chimeric BALB/c mice did not suffer from AIG, they brought immediate precursors of T cells for AIG. It is concluded that DBA/2 mice generate bone marrow-derived cells that produce anti-inflammatory cytokines to prevent the activation of AIG-T cells.

Interleukin-21 and tumor necrosis factor-α are critical for the development of autoimmune gastritis in mice

BACKGROUND AND AIM

Autoimmune gastritis (AIG), an organ-specific autoimmune disease, is accompanied by achlorhydria, pernicious anemia, gastric carcinoid tumors, and gastric cancer. Patients with AIG initially respond to corticosteroids but have a great potential to relapse after treatment is withdrawn. This study examines the roles of cytokines in order to identify potential therapeutic options for AIG patients.

METHODS

Using a mouse model of AIG, we monitored disease progression and administered antibodies in vivo to block cytokines.

RESULTS

We developed a mouse model of AIG with early onset and rapid progression in which neonatal thymectomy (NTx) was performed on programmed cell death 1-deficient (PD-1(-/-) ) mice on the BALB/c background. Using NTx-PD-1(-/-) mice, we found that in AIG lesions, interferon-γ, and tumor necrosis factor (TNF)-α together with interleukin-21 (IL-21) were highly expressed in the inflamed gastric mucosa. In addition, as with the injection of dexamethasone, in vivo administration of either anti-TNF-α or anti-IL-21 suppressed the development of AIG in NTx-PD-1(-/-) mice.

CONCLUSIONS

These data reveal the essential role of IL-21 in the development of AIG and suggest that in addition to corticosteroids, anti-TNF-α as well as anti-IL-21 have the potential to induce the remission of AIG, offering additional therapeutic options for AIG patients.

Cutting edge issues in autoimmune gastritis

Autoimmune gastritis is the outcome of a pathological CD4 T cell-mediated autoimmune response directed against the gastric H/K-ATPase. Silent initially, the gastric lesion becomes manifest in humans by the development of megaloblastic pernicious anemia arising from vitamin B12 deficiency. Cutting edge issues in this disease relate to its epidemiology, immunogenetics, a role for Helicobacter pylori as an infective trigger through molecular mimicry, its immunopathogenesis, associated organ-specific autoimmune diseases, laboratory diagnosis, and approaches to curative therapy.

The Biology of Autoimmune Response in the Scurfy Mice that Lack the CD4+Foxp3+ Regulatory T-Cells

Due to a mutation in the Foxp3 transcription factor, Scurfy mice lack regulatory T-cells that maintain self-tolerance of the immune system. They develop multi-organ inflammation (MOI) and die around four weeks old. The affected organs are skin, tail, lungs and liver. In humans, endocrine and gastrointestinal inflammation are also observed, hence the disease is termed IPEX (Immunodysregulation, Polyendocrinopathy, Enteropathy, X-linked) syndrome. The three week period of fatal MOI offers a useful autoimmune model in which the controls by genetics, T-cell subsets, cytokines, and effector mechanisms could be efficiently investigated. In this report, we will review published work, summarize our recent studies of Scurfy double mutants lacking specific autoimmune-related genes, discuss the cellular and cytokine controls by these genes on MOI, the organ-specificities of the MOI controlled by environments, and the effector mechanisms regulated by specific Th cytokines, including several newly identified control mechanisms for organ-specific autoimmune response.

Thymus-associated parathyroid hormone has two cellular origins with distinct endocrine and immunological functions

In mammals, parathyroid hormone (PTH) is a key regulator of extracellular calcium and inorganic phosphorus homeostasis. Although the parathyroid glands were thought to be the only source of PTH, extra-parathyroid PTH production in the thymus, which shares a common origin with parathyroids during organogenesis, has been proposed to provide an auxiliary source of PTH, resulting in a higher than expected survival rate for aparathyroid Gcm2^−/− mutants. However, the developmental ontogeny and cellular identity of these “thymic” PTH–expressing cells is unknown. We found that the lethality of aparathyroid Gcm2^−/− mutants was affected by genetic background without relation to serum PTH levels, suggesting a need to reconsider the physiological function of thymic PTH. We identified two sources of extra-parathyroid PTH in wild-type mice. Incomplete separation of the parathyroid and thymus organs during organogenesis resulted in misplaced, isolated parathyroid cells that were often attached to the thymus; this was the major source of thymic PTH in normal mice. Analysis of thymus and parathyroid organogenesis in human embryos showed a broadly similar result, indicating that these results may provide insight into human parathyroid development. In addition, medullary thymic epithelial cells (mTECs) express PTH in a Gcm2-independent manner that requires TEC differentiation and is consistent with expression as a self-antigen for negative selection. Genetic or surgical removal of the thymus indicated that thymus-derived PTH in Gcm2^−/− mutants did not provide auxiliary endocrine function. Our data show conclusively that the thymus does not serve as an auxiliary source of either serum PTH or parathyroid function. We further show that the normal process of parathyroid organogenesis in both mice and humans leads to the generation of multiple small parathyroid clusters in addition to the main parathyroid glands, that are the likely source of physiologically relevant “thymic PTH.”

Due to the important role of PTH in the regulation of physiological activities, disorders in PTH production can cause many diseases in humans. Thus it is very important to understand where PTH is produced and how it is regulated. Many people have been found to have ectopic and supernumerary parathyroid glands without clear ontogenesis. In addition, the thymus, which develops together with the parathyroid during embryogenesis, has been proposed to be an auxiliary source of PTH with endocrine function; however, PTH is also a tissue-restricted self-antigen expressed by the thymus. In this paper, we provide insights into the ontogeny and function of thymus-associated PTH. We found that ectopic and supernumerary parathyroid glands originate from the normal developmental process underlying the separation of parathyroid and thymus, resulting in misplaced parathyroids close or attached to thymus. In the thymus, thymic epithelial cells can produce a low level of PTH via a different mechanism than the parathyroid and provide functional data that TEC-derived PTH does not have endocrine function. In summary, our data show that the thymic source of PTH has no endocrine function and, instead, has an expression pattern in the thymus consistent with that of a self-antigen for negative selection.

Reversing the Autoimmune Condition: Experience with Experimental Autoimmune Gastritis

Autoimmune diseases remain a significant health problem in our society, despite the best efforts to understand and treat these conditions. Current clinical treatments are aimed at alleviating the consequences of these diseases, with limited prospects for cure. Our studies with the experimental model of autoimmune gastritis have led us to explore potential curative strategies that can reverse the autoimmune condition. Using mouse models, we have shown that expression of the known gastric autoantigen in the thymus results in immunological tolerance and resistance to the induction of autoimmune gastritis. Also, induced tolerance in donor mice can be transferred to syngeneic recipient mice by bone marrow cells. Strategies based on these observations could lead to reversal of established disease. Transfer of ensuing knowledge to the cure of serious human autoimmune diseases is our ultimate goal.

Experimental Autoimmune Gastritis: Mouse Models Of Human Organ-specific Autoimmune Disease

Experimental autoimmune gastritis (EAG) is an excellent model of human autoimmune gastritis, the underlying cause of pernicious anaemia. Murine autoimmune gastritis replicates human gastritis in being characterized by a chronic inflammatory mononuclear cell infiltrate in the gastric mucosa, destruction of parietal and zymogenic cells, and autoantibodies to the alpha-and beta-subunits of the gastric H+/K+ ATPase. Disease is induced strain specifically in gastritis-susceptible BALB/c mice by methods with a greater variety than those for most other experimental autoimmune diseases. The disease is induced in the regional gastric lymph node in which pathogenic CD4+ T cells are recruited. The model provides an excellent illustration of regulation by CD4+CD25+T cells, and, indeed, the removal of such regulatory cells, e.g., by neonatal thymectomy, is thought to be a major mechanism by which disease can develop. The culprit T helper type 1 (Th1) CD4+ T cells recognize either the alpha- or beta-subunits of the gastric H+/K+ ATPase, but the beta-subunit appears to be the initiating autoantigen, while the alpha-subunit may have a role in perpetuating disease. Since no specific environmental modifiers are identifiable, the origins of the disease are intrinsic; this is illustrated by the capacity of a cytokine (GM-CSF)-dependent inflammatory stimulus in the stomach to initiate EAG, according to a transgenic model in which thymectomy is dispensible. Thus, EAG is an exquisite model for a reductionist analysis of the multiple elements that in combination induce autoimmunity in humans.

Autoimmune Gastritis: Tolerance and Autoimmunity to the Gastric H+/K+Atpase (Proton Pump)

The alpha and beta subunits of the gastric H+/K(+)-ATPase (proton pump) have been identified as the major molecular targets of parietal cell autoantibodies associated with pernicious anaemia and with murine experimental autoimmune gastritis (EAG) induced by neonatal thymectomy. Recent studies with EAG suggest that the mechanisms of peripheral tolerance and autoimmunity to extrathymic autoantigens are mediated by subsets of "regulator" and "effector" CD4+ T cells, respectively. The persistence of "effector" CD4+ autoreactive T cells in the periphery may be a direct consequence of the delayed developmental expression of the target autoantigen. We hypothesize that cytokines produced by the "regulator" T cells prevent the clonal expansion of the "effector" autoreactive T cells, and that neonatal thymectomy induces organ-specific autoimmunity in genetically susceptible individuals by the reduction of the "regulator" T cell population.

Regulation of multi-organ inflammation in the regulatory T cell-deficient scurfy mice

Scurfy mice display the most severe form of multi-organ inflammation due to total lack of the CD4+Foxp3+ regulatory T cells (Treg) resulted from a mutation of the X-linked transcription factor Foxp3. A large repertoire of Treg-suppressible, inflammation-inducing T cells was demonstrated by adoptive transfer experiments using Rag1-/- mice as recipients and by prolongation of lifespan through breeding with Faslpr/lpr mutant. Inflammation in the ear, eyes, skin, tail, salivary glands, lungs, stomach, pancreas, liver, small intestine, colon, skeletal muscle, and accessory reproductive organs are identified. Genetic and cellular regulations of specific organ inflammation are described. Sf mice may be useful for the identification of organ-specific antigens and Treg capable of suppressing inflammation in an organ-specific manner. Sf mice are also useful to determine the important inflammation process at the checkpoint after Treg regulation using genetic analysis through breeding.

Availability of autoantigenic epitopes controls phenotype, severity, and penetrance in TCR Tg autoimmune gastritis

We examined TCR:MHC/peptide interactions and in vivo epitope availability to explore the Th1- or Th2-like phenotype of autoimmune disease in two TCR Tg mouse models of autoimmune gastritis (AIG). The TCR of strains A23 and A51 recognize distinct IA(d)-restricted peptides from the gastric parietal cell H/K-ATPase. Both peptides form extremely stable MHC/peptide (MHC/p) complexes. All A23 animals develop a Th1-like aggressive, inflammatory AIG early in life, while A51 mice develop indolent Th2-like AIG at 6-8 wk with incomplete penetrance. A51 T cells were more sensitive than A23 to low doses of soluble antigen and to MHC/p complexes. Staining with IA(d)/peptide tetramers was only detectable on previously activated T cells from A51. Thus, despite inducing a milder AIG, the A51 TCR displays a higher avidity for its cognate IA(d)/peptide. Nonetheless, in vivo proliferation of adoptively transferred A51 CFSE-labeled T cells in the gastric lymph node was relatively poor compared with A23 T cells. Also, DC from WT gastric lymph node, presenting processed antigen available in vivo, stimulated proliferation of A23 T cells better than A51. Thus, the autoimmune potential of these TCR in their respective Tg lines is strongly influenced by the availability of the peptide epitope, rather than by differential avidity for their respective MHC/p complexes.

Activation-induced cytidine deaminase deficiency causes organ-specific autoimmune disease

Activation-induced cytidine deaminase (AID) expressed by germinal center B cells is a central regulator of somatic hypermutation (SHM) and class switch recombination (CSR). Humans with AID mutations develop not only the autosomal recessive form of hyper-IgM syndrome (HIGM2) associated with B cell hyperplasia, but also autoimmune disorders by unknown mechanisms. We report here that AID-/- mice spontaneously develop tertiary lymphoid organs (TLOs) in non-lymphoid tissues including the stomach at around 6 months of age. At a later stage, AID-/- mice develop a severe gastritis characterized by loss of gastric glands and epithelial hyperplasia. The disease development was not attenuated even under germ-free (GF) conditions. Gastric autoantigen -specific serum IgM was elevated in AID-/- mice, and the serum levels correlated with the gastritis pathological score. Adoptive transfer experiments suggest that autoimmune CD4+ T cells mediate gastritis development as terminal effector cells. These results suggest that abnormal B-cell expansion due to AID deficiency can drive B-cell autoimmunity, and in turn promote TLO formation, which ultimately leads to the propagation of organ-specific autoimmune effector CD4+ T cells. Thus, AID plays an important role in the containment of autoimmune diseases by negative regulation of autoreactive B cells.

Autoantigen-specific TGFbeta-induced Foxp3+ regulatory T cells prevent autoimmunity by inhibiting dendritic cells from activating autoreactive T cells

Several strategies are being designed to test the therapeutic potential of Ag-specific regulatory T cells to prevent or treat autoimmune diseases. In this study, we demonstrate that naive CD4+ Foxp3- T cells specific for a naturally expressed autoantigen (H+/K+ ATPase) can be converted to Foxp3+ T regulatory cells (Tregs) when stimulated in presence of TGFbeta. TGFbeta-induced Tregs (iTregs) have all the characteristics of naturally generated regulatory T cells in vitro, and more importantly, are effective at preventing organ-specific autoimmunity in a murine model of autoimmune gastritis. H+/K+ ATPase specific iTregs were able to inhibit the initial priming and proliferation of autoreactive T cells, and appear to do so by acting on H+/K+ ATPase presenting dendritic cells (DC). DC exposed to iTregs in vivo were reduced in their ability to stimulate proliferation and cytokine production by H+/K+ ATPase specific T cells. iTregs specifically reduced CD80 and CD86 expression on the surface of H+/K+ ATPase presenting DC in vitro. These studies reveal the therapeutic potential of Ag specific iTregs to prevent autoimmunity, and provide a mechanism by which this population of regulatory T cells, and perhaps others, mediate their suppressive effects in vivo.

Spontaneous large-scale lymphoid neogenesis and balanced autoimmunity versus tolerance in the stomach of H+/K+-ATPase-reactive TCR transgenic mouse

Autoimmunity is often accompanied by the development of ectopic lymphoid tissues in the target organ, and these tissues have been believed to have close relevance to the severity of the disease. However, the true relationship between the extent of such lymphoid structures and the intensity or type of immune responses mediated by self-reactive T cells has remained unclear. In the present study, we generated transgenic mice expressing TCR from an autoimmune gastritis (AIG)-inducing Th1 cell clone specific for one of the major stomach self-Ags, H(+)/K(+)-ATPase alpha subunit. The transgenic mice spontaneously develop massive lymphoid neogenesis with a highly organized tissue structure in the gastric mucosa, demonstrating Ag-specific, T cell-mediated induction of the lymphoid tissues. Nevertheless, the damage of surrounding tissue and autoantibody production were considerably limited compared with those in typical AIG induced by neonatal thymectomy. Such a moderate pathology is likely due to the locally restricted activation and Th2 skewing of self-reactive T cells, as well as the accumulation of naturally occurring regulatory T cells in the target organ. Altogether, the findings suggest that lymphoid neogenesis in chronic autoimmunity does not simply correlate with the destructive response; rather, the overall activation status of the T cell network, i.e., the balance of self-reactivity and tolerance, in the local environment has an impact.

Murine experimental autoimmune gastritis models refractive to development of intrinsic factor autoantibodies, cobalamin deficiency and pernicious anemia

Researchers have developed murine lymphopenic, non-lymphopenic, transgenic, spontaneous and infectious agent based models to induce an experimental autoimmune gastritis (EAG) for the study of human organ-specific autoimmune disease. These models result in a chronic inflammatory mononuclear cell infiltrate in the gastric mucosa, destruction of parietal and zymogenic cells with autoantibodies reactive to the gastric parietal cells and the gastric H+/K+ ATPase (ATP4), arguably hallmarks of a human autoimmune gastritis (AIG). In the case of AIG, it is well documented that, in addition to parietal cell antibodies being detected in up to 90% of patients, up to 70% have intrinsic factor antibodies with the later antibodies considered highly specific to patients with pernicious anemia. This is the first report specifically investigating the occurrence of intrinsic factor antibodies, cobalamin deficiency and pernicious anemia in EAG models. We conclude, in contrast to AIG, that, in the three EAG models examined, intrinsic factor is not selected as a critical autoantigen.

Human regulatory T cells and their role in autoimmune disease

As self-recognition is fundamental to the efficient operation of the immune system, a number of mechanisms have evolved to keep this potential pathologic self-reactivity in check. Thus, even though the majority of strongly self-reactive T cells are deleted in the thymus during T-cell maturation, a number of mature T cells that recognize self-antigens can be found in the peripheral circulation in healthy individuals as well as in patients with autoimmune disease. These self-reactive cells are kept in a non-responsive state in healthy individuals while they appear to be involved in the etiology of a number of autoimmune diseases in patients. The primary role of a relatively recently identified T-cell population, referred to as natural CD4+ CD25+ regulatory T cells, is to modulate the activity of these self-reactive cells. Although it is still unclear how these regulatory cells function, they can inhibit the activation of other potentially pathologic T cells in in vitro assays. Using such assays, regulatory T cells isolated from patients with a number of autoimmune diseases have been shown to exhibit reduced inhibitory function as compared with those isolated from healthy individuals. In this review, we discuss human natural regulatory T cells, what is known about their function, and their associations with specific autoimmune diseases.

Oral tolerance

Multiple mechanisms of tolerance are induced by oral antigen. Low doses favor active suppression, whereas higher doses favor clonal anergy/deletion. Oral antigen induces T-helper 2 [interleukin (IL)-4/IL-10] and Th3 [transforming growth factor (TGF)-beta] T cells plus CD4+CD25+ regulatory cells and latency-associated peptide+ T cells. Induction of oral tolerance is enhanced by IL-4, IL-10, anti-IL-12, TGF-beta, cholera toxin B subunit, Flt-3 ligand, and anti-CD40 ligand. Oral (and nasal) antigen administration suppresses animal models of autoimmune diseases including experimental autoimmune encephalitis, uveitis, thyroiditis, myasthenia, arthritis, and diabetes in the non-obese diabetic (NOD) mouse, plus non-autoimmune diseases such as asthma, atherosclerosis, graft rejection, allergy, colitis, stroke, and models of Alzheimer's disease. Oral tolerance has been tested in human autoimmune diseases including multiple sclerosis (MS), arthritis, uveitis, and diabetes and in allergy, contact sensitivity to dinitrochlorobenzene (DNCB), and nickel allergy. Although positive results have been observed in phase II trials, no effect was observed in phase III trials of CII in rheumatoid arthritis or oral myelin and glatiramer acetate (GA) in MS. Large placebo effects were observed, and new trials of oral GA are underway. Oral insulin has recently been shown to delay onset of diabetes in at-risk populations, and confirmatory trials of oral insulin are being planned. Mucosal tolerance is an attractive approach for treatment of autoimmune and inflammatory diseases because of lack of toxicity, ease of administration over time, and antigen-specific mechanisms of action. The successful application of oral tolerance for the treatment of human diseases will depend on dose, developing immune markers to assess immunologic effects, route (nasal versus oral), formulation, mucosal adjuvants, combination therapy, and early therapy.

Helicobacter felis-induced gastritis was suppressed in mice overexpressing thioredoxin-1

Thioredoxin-1 (TRX-1) is a redox-active protein involved in scavenging reactive oxygen species and regulating redox-sensitive transcription factors. TRX-1 is induced in various inflammatory conditions and shows cytoprotective action. We investigated the roles of TRX-1 in the host defense mechanism against Helicobacter felis (H. felis) infection. Transgenic (TG) mice overexpressing human TRX-1 and wild-type (WT) mice were orally inoculated with H. felis. After 2 months, histology, oxidative damage, and gene expression of several cytokines, including macrophage inflammatory protein-2 (MIP-2), a murine equivalent to interleukin (IL)-8, in the gastric mucosa were investigated. Furthermore, the effects of TRX-1 on oxidative stress and neutrophil migration were studied both in vivo and in vitro. The gastric mucosa was thickened in H. felis-infected WT mice, but not in infected TRX-1-TG mice. Histologically, all H. felis-infected WT mice developed moderate-to-severe gastritis, whereas the development of gastritis was significantly suppressed in infected TRX-1-TG mice. Oxidative damage markers, 8-hydroxy-2'-deoxyguanosine and malondialdehyde, increased in the stomach of infected WT mice, but not TRX-1-TG mice. Upregulation of IL-1beta and tumor necrosis factor-alpha gene expression in H. felis-infected TRX-1-TG mice was significantly lower than in WT mice. However, upregulation of MIP-2 and IL-7 was not different between the two groups. TRX-1 suppressed oxidative cytotoxicity and DNA damage, and inhibited neutrophil migration both in vivo and in vitro. The present study suggests that overexpression of TRX-1 suppresses H. felis-induced gastritis by inhibiting chemotaxis of neutrophils and reducing oxidative stress.

Immunological and morphogenic basis of gastric mucosa atrophy and metaplasia

Chronic gastritis with gastric mucosa atrophy, intestinal metaplasia and endocrine cell hyperplasia are alterations with an increased risk for the development of gastric neoplasias. Immunological studies in autoimmune gastritis, in atrophic Helicobacter pylori gastritis and in studies with transgenic mice point to a central role of the parietal cell in the development of gastric mucosa atrophy. Destruction of gastric epithelial cells alone might not be sufficient for the loss of complete gastric glands. Gastric atrophy, endocrine cell hyperplasia and intestinal and pancreatic metaplasia can be regarded as the result of altered morphogenesis within the gastric mucosa. Impaired expression of the gastric morphogenic factor Sonic Hedgehog by parietal cells and increased expression of the transcriptional activators of intestinal and pancreatic differentiation, namely CDX2 and PDX1, seem to be crucial for the development of gastric atrophy and for intestinal, endocrine and pancreatic transdifferentiation processes. Altered expression of these morphogenic factors is partly caused by changes in the gastric milieu. Further studies concerning the normal and pathological morphogenesis of the gastric mucosa and related tissues might give new insight into the pathogenesis of gastric atrophy and metaplasia.

CD4+CD45RBHi interleukin-4 defective T cells elicit antral gastritis and duodenitis

We have analyzed the gastrointestinal inflammation which develops following adoptive transfer of IL-4 gene knockout (IL-4(-/-)) CD4(+)CD45RB(Hi) (RB(Hi)) T cells to severe combined immunodeficient (SCID) or to T cell-deficient, T cell receptor beta and delta double knockout (TCR(-/-)) mice. Transfer of IL-4(-/-) RB(Hi) T cells induced a similar type of colitis to that seen in SCID or TCR(-/-) recipients of wild-type (wt) RB(Hi) T cells as reported previously. Interestingly, transfer of both wt and IL-4(-/-) RB(Hi) T cells to TCR(-/-) but not to SCID mice induced inflammation in the gastric mucosa. Notably, TCR(-/-) recipients of IL-4(-/-) RB(Hi) T cells developed a more severe gastritis with erosion, apoptosis of the antral epithelium, and massive infiltration of macrophages. This gastritis was partially dependent on the indigenous microflora. Recipients of both wt and IL-4(-/-) RB(Hi) T cells developed duodenitis with multinuclear giant cells, expansion of mucosal macrophages, and dendritic cells. Full B cell responses were reconstituted in TCR(-/-) recipients of RB(Hi) T cells; however, anti-gastric autoantibodies were not detected. We have now developed and characterized a novel model of chronic gastroduodenitis in mice, which will help in our understanding of the mechanisms involved in chronic inflammation in the upper gastrointestinal tract of humans.

Chemokine receptor CCR5 is not required for development of experimental autoimmune gastritis

Experimental autoimmune gastritis (EAG) is a model of human autoimmune gastritis, the underlying cause of pernicious anaemia. It is characterised by gastric mononuclear cell infiltrates, destruction of parietal and zymogenic cells, and autoantibodies to parietal cell-associated H(+)/K(+) ATPase. Here, we have investigated the role of CCR5 in the development of EAG. We found that the development of EAG was not prevented in CCR5-deficient mice. Using reverse-transcriptase analysis of stomachs from normal and gastritic mice we found no difference in expression of CCR5 and its chemokine ligands MIP-1alpha, MIP-1beta, and RANTES. We also found that the CCR5 antagonist met-RANTES failed to prevent the development of EAG induced by neonatal thymectomy. These observations suggest that the CC chemokine receptor CCR5 is not essential for development of EAG.

HK-ATPase expression in the susceptible BALB/c and the resistant DBA/2 strains of mice to autoimmune gastritis

Neonatal thymectomy (NTx) in mice induces a group of alterations in the immune system homeostasis that results in the development of a variety of organ-specific autoimmune diseases such as gastritis, thyroiditis, oophoritis and orchitis. Given the importance of self-antigen expression in thymus for the control of autoreactive cells and generation of regulatory cells, we have compared the expression of parietal cell antigen in two strains of mice with the same H-2: BALB/c (susceptible to develop gastritis after NTx) and DBA/2 (resistant). We detected mRNA of HK-ATPase alpha and beta chains in day 1 thymi of both strains. Fifty percent of BALB/c mice presented mRNA levels similar to DBA/2. However, lower mRNA levels were found in the remaining BALB/c mice that may correspond to those that would develop AIG after NTx. Since the presence of the antigen in periphery is also necessary for the induction of regulatory cells, we have compared both strains observing in day 1 stomachs from resistant DBA/2 strain, a significantly higher content of positive cells for HK-ATPase subunits than stomachs from susceptible BALB/c strain. Also, the presence of antinuclear Abs in NTx BALB/c mice makes this model a useful experimental system for analyzing the responsible mechanisms breaking the non-specific self-tolerance.

Endogenous H/K ATPase beta-subunit promotes T cell tolerance to the immunodominant gastritogenic determinant

A CD4(+) T cell response to the gastric H/K ATPase beta-subunit (H/Kbeta) is required for the onset of experimental autoimmune gastritis in BALB/c mice. The extent to which endogenous H/Kbeta contributes toward the tolerance of the H/Kbeta-specific T cell repertoire in normal individuals is not known. By comparison of T cell responses in H/Kbeta-deficient (o/o) and H/Kbeta-expressing BALB/c mice, in this work we show that the endogenous H/Kbeta autoantigen plays a major role in the tolerance of pathogenic H/Kbeta-specific T cells. First, T cell-dependent Ab responses to the H/Kbeta Ag were enhanced in H/K ATPase-immunized H/Kbeta-deficient mice compared with wild-type mice. Second, peptide immunization experiments indicated that immune responses to the major gastritogenic epitope of the H/K ATPase, namely H/Kbeta(253-277), were significantly more vigorous in H/Kbeta-deficient mice compared with wild-type mice. Third, unfractionated splenocytes from H/Kbeta-deficient mice, but not H/Kbeta-expressing mice, induced autoimmune gastritis after adoptive transfer to BALB/c nude mice. The enhanced responses to H/Kbeta in H/Kbeta-deficient mice were shown to be intrinsic to CD4(+)CD25(-) T cells rather than a change in status of CD4(+)CD25(+) regulatory T cells. We conclude from these studies that the H/Kbeta-specific T cells in wild-type mice represent the residue of a T cell repertoire, directed toward a single determinant, that has been subjected to partial tolerance induction.

Selective accumulation of type 1 effector cells expressing P-selectin ligand and/or alpha(4)beta(7)-integrin at the lesions of autoimmune gastritis

T(h)1 cells but not T(h)2 cells accumulate at the inflamed gastric mucosa (GM), while both subsets co-exist in the regional lymph node (RLN) in a murine experimental model for autoimmune gastritis (AIG). To understand the relationship between the immuno-microenvironment and effector localization in GM versus RLN of AIG-bearing mice, cells or tissue sections were stained with several mAb against adhesion molecules. The expression of RNA of various cytokines at these contrasting sites was also assessed. IFN-gamma-producing memory CD4(+) (T(h)1) and CD8(+) T cells as well as IL-12-producing mature macrophages which express P-selectin ligand and/or alpha(4)beta(7)-integrin selectively accumulated in the inflamed GM. Vessel endothelium at the site of infiltration expressed those counter-receptors, P-selectin and mucosal adressin cell adhesion molecule-1. Therefore, the tissue destruction of target tissue in autoimmune diseases might be promoted by a vicious circle between the selective accumulation of type 1 effectors mediated by multiple adhesion molecules and following an unusual type 1-biased microenvironment away from the type 2 response.

Animal models of human disease: experimental autoimmune gastritis--a model for autoimmune gastritis and pernicious anemia

Human autoimmune gastritis is an organ-specific autoimmune disease of the stomach. It is characterized by the development of disease-specific autoantibodies and a pathology that specifically targets specialized cells within the gastric environment. The autoantigens associated with this disease have been defined as the gastric H+/K+ ATPase and intrinsic factor. The development of experimental disease models has been pivotal in our contemporary understanding of autoimmunity. Here we review mouse models of autoimmune gastritis and their relevance to human autoimmune gastritis associated with pernicious anemia. We appraise some historical as well as recent studies of experimental autoimmune gastritis (EAG), highlighting key findings that have formed the basis of our current understanding of the etiology and mechanism(s) associated with autoimmune gastritis. A precise understanding of the pathogenesis of autoimmune gastritis will permit the design of innovative and rational therapeutic strategies to prevent, arrest, ameliorate or reverse the disease.

Requirements for autoimmune responses to mouse gastric autoantigens

Autoimmune gastritis, in which the H+/K(+)-ATPase of parietal cells is the major antigen, is one of the most common autoimmune diseases. Here we examined if specific properties of the H+/K(+)-ATPase or parietal cells are involved in rendering them autoimmune targets. The model antigens beta-galactosidase and ovalbumin (OVA) were expressed in parietal cells of transgenic mice. On experimental induction of autoimmune gastritis by neonatal thymectomy, autoantibodies to beta-galactosidase developed in mice expressing beta-galactosidase in parietal cells, a response that was independent of either the response to the gastric H+/K(+)-ATPase or gastric inflammation. In contrast, mice that expressed OVA in parietal cells did not exhibit an antibody response to OVA after thymectomy. However, increasing the frequency of anti-OVA T lymphocytes in OVA-expressing mice resulted in autoantibodies to OVA and gastritis. These studies indicate that parietal cells can present a variety of antigens to the immune system. Factors such as the identity and expression level of the autoantigen and the frequency of autoreactive T cells play a role in determining the prevalence and outcome of the particular immune response. In addition, as not all mice of a particular genotype displayed autoimmunity, random events are involved in determining the target of autoimmune recognition.

Defining T cell receptors which recognise the immunodominant epitope of the gastric autoantigen, the H/K ATPase beta-subunit

We have previously shown that autoimmune gastritis can be elicited in mice by immunisation with the gastric parietal cell H/K ATPase alphabeta heterodimer, and, furthermore, have identified the H/K ATPase beta-subunit epitope, H/Kbeta253-277 as the dominant epitope of the gastric H/K ATPase. Using gastric H/K ATPase-immunised mice, here we have generated two T cell hybridomas specific for the H/Kbeta253-277 peptide, namely 4B11.F4.5 and 1E4.C1. Hybridoma 4B11.F4.5 uses Valpha8 and Vbeta8.2 TCR chains and 1E4.C1 uses Valpha9 and V1beta8.3 chains. Although both hybridomas are specific for H/Kbeta253-277, T cell assays using overlapping 14-mers of the 25-mer epitope showed that the two autoreactive TCRs recognise different regions of the 25-mer. The TCR from 1E4.C1 has been used to generate a TCR beta-chain transgenic mouse. >80% of peripheral CD4+ T cells utilise the Vbeta8.3 transgene. As expected, 1E4-TCR beta-chain transgenic mice are susceptible to neonatal thymectomy induced autoimmune gastritis. While none of the 1E4-TCR beta chain transgenic mice spontaneously developed a destructive gastritis, a minority (20%) of the transgenic mice developed a non-invasive and non-destructive gastritis. This suggests that the pathogenic T cells are maintained in a tolerant state in the periphery of the transgenic mice.

Local transgenic expression of granulocyte macrophage-colony stimulating factor initiates autoimmunity

Mechanisms leading to breakdown of immunological tolerance and initiation of autoimmunity are poorly understood. Experimental autoimmune gastritis is a paradigm of organ-specific autoimmunity arising from a pathogenic autoimmune response to gastric H/K ATPase. The gastritis is accompanied by autoantibodies to the gastric H/K ATPase. The best characterized model of experimental autoimmune gastritis requires neonatal thymectomy. This procedure disrupts the immune repertoire, limiting its usefulness in understanding how autoimmunity arises in animals with intact immune systems. Here we tested whether local production of GM-CSF, a pro-inflammatory cytokine, is sufficient to break tolerance and initiate autoimmunity. We generated transgenic mice expressing GM-CSF in the stomach. These transgenic mice spontaneously developed gastritis with an incidence of about 80% after six backcrosses to gastritis-susceptible BALBc/CrSlc mice. The gastritis is accompanied by mucosal hypertrophy, enlargement of draining lymph nodes and autoantibodies to gastric H/K ATPase. An infiltrate of dendritic cells and macrophages preceded CD4 T cells into the gastric mucosa. T cells from draining lymph nodes specifically proliferated to the gastric H/K ATPase. CD4 but not CD8 T cells transferred gastritis to nude mouse recipients. CD4(+) CD25(+) T cells from the spleen retained anergic suppressive properties that were reversed by IL-2. We conclude that local expression of GM-CSF is sufficient to break tolerance and initiate autoimmunity mediated by CD4 T cells. This new mouse model should be useful for studies of organ-specific autoimmunity.

Localization and characterization of antigen-presenting dendritic cells in the gastric mucosa of murine and human autoimmune gastritis

BACKGROUND

Activated CD4+ T cells and inflammatory cytokines are implicated in the pathogenesis of experimental autoimmune gastritis. However, there is a paucity of information about the cells that induce them. Antigen-presenting dendritic cells (DCs) play a cardinal role in the formation and survival of activated lymphocytes.

MATERIALS AND METHODS

Autoimmune gastritis was induced in neonatal BALB/c mice by thymectomy. DCs were detected in situ in the gastric mucosa from thymectomized mice and in patients with autoimmune gastritis, by immunohistochemistry and immunoelectron microscopy. The expression of MHC class II and CD86 antigens on DCs in the gastric mucosa and spleen was evaluated in dual-colour flow cytometry.

RESULTS

DCs were detected in the gastric mucosa of mice with autoimmune gastritis, and the number of DCs increased as the levels of gastritis became more severe as time passed following thymectomy. Flow cytometric analyses revealed that more than 60% of the DCs in the gastric mucosa had a mature phenotype (expressed MHC class II and/or CD86 antigens) both at 4 and 16 weeks after thymectomy. Activated and mature DCs were localized in the gastric mucosa from patients with autoimmune gastritis.

CONCLUSIONS

This is the first report on the localization and phenotypes of DCs in the gastric mucosa of autoimmune gastritis. The presence of mature DCs in the gastric mucosa of murine and human autoimmune gastritis, in spite of their absence in the gastric mucosa of normal mice, suggests that mature DCs play a role in the pathogenesis of autoimmune gastritis.

Tolerance and autoimmunity to a gastritogenic peptide in TCR transgenic mice

The catalytic alpha and glycoprotein beta subunits of the gastric H/K ATPase are major molecular targets in human and mouse autoimmune gastritis. We have previously shown that the H/K ATPase beta subunit is required for the initiation of mouse gastritis and identified a gastritogenic H/K ATPase beta subunit peptide (H/Kbeta253-277). Here we report the generation of MHC class II-restricted TCR transgenic mice using V(alpha)9 and V(beta)8.3 TCR chains with specificity for the gastritogenic H/Kbeta253-277 peptide. We found an 8-fold reduction in CD4(+) T cells in the thymus of the transgenic mice. Despite the reduction in intrathymic CD4(+) T cells, V(beta)8. 3-expressing T cells comprised the majority (>90%) of peripheral spleen and lymph node T cells. These peripheral T cells retained their capacity to proliferate in vitro to the H/Kbeta253-277 peptide. Using the responsive T cells, we have restricted the gastritogenic T cell epitope to H/Kbeta261-274. Despite the capacity of the peripheral T cells to proliferate in vitro to the peptide, the majority ( approximately 80%, 13 of 16) of transgenic mice remained free of gastritis while a minority (20%, three of 16) spontaneously developed an invasive and destructive gastritis. Our results confirm that H/Kbeta261-274 is a gastritogenic peptide. The data also suggest that CD4 T cell tolerance to the gastritogenic peptide in the transgenic mice is maintained by a combination of intrathymic and peripheral tolerance mechanisms.

Post-thymectomy autoimmune gastritis: fine specificity and pathogenicity of anti-H/K ATPase-reactive T cells

Thymectomy at day 3 of life (d3Tx) results in the development of organ-specific autoimmunity. We have recently shown that d3Tx BALB/c mice which develop autoimmune gastritis contain CD4+ T cells specific for the gastric parietal cell proton pump, H/K ATPase. Here, we demonstrate that freshly explanted gastric lymph node (LN) cells from d3Tx mice react significantly to the H/K ATPase alpha chain, but only marginally to the beta chain. Two H/K ATPase-reactive T cell lines were derived from the gastric LN of d3Tx mice. Both are CD4+, TCR alpha/beta-, and I-Ad restricted, and recognize distinct peptides from the H/K ATPase alpha chain. One cell line secretes Th1 and the other Th2 cytokines, but both are equally potent in inducing gastritis with distinct profiles of cellular infiltration in nu/nu recipient animals. Neither of the cell lines induced disease in normal BALB/c recipients and transfer of disease to nu/nu recipients was blocked by co-transfer of normal BALB/c spleen cells containing CD4+ CD25+ cells. Although CD4+ CD25+ T cells are thought to emigrate from the thymus after day 3 of life, they could be identified in LN of 2-day-old animals. The capacity of CD4+ CD25+ T cells to abrogate the pathogenic activity in vivo of both activated Th1/Th2 lines strongly suggests that this suppressor T cell population may have a therapeutic role in other models of established autoimmunity. The availability of well-characterized lines of autoantigen-specific T cells should greatly facilitate the analysis of the mechanism of action and target of the CD4+ CD25+ immunoregulatory cells.

Identification of a gastritogenic epitope of the H/K ATPase beta-subunit

We have previously shown that autoimmune gastritis can be elicited in mice by immunization with the gastric parietal cell H/K ATPase alpha beta heterodimer and that tolerance specifically induced to the H/K ATPase beta-subunit protects mice from the development of gastritis. Here we have identified the immunodominant gastritogenic epitope of the H/K ATPase beta-subunit (H/Kbeta). Epitope mapping was carried out with a panel of 21 overlapping peptides that spanned the entire sequence of the gastric H/K ATPase beta-subunit. T cells from gastric H/K ATPase-immunized mice responded to only one of the overlapping peptides, namely H/Kbeta253-277. Furthermore, a single subcutaneous immunization of 6-week-old BALB/c mice with the ATPase beta-subunit peptides resulted in a T-cell response to only H/Kbeta253-277. Multiple immunization with the overlapping H/K ATPase peptides demonstrated that H/Kbeta253-277 was capable of inducing a mononuclear infiltrate specifically within the gastric mucosa. We conclude that H/Kbeta253-277 is the dominant gastritogenic epitope of the gastric H/K ATPase.

Gastrointestinal hormones as potential adjuvant treatment of exocrine pancreatic adenocarcinoma

CONCLUSION

Gastrointestinal hormones and their antagonists can alter the growth of pancreatic adenocarcinoma in vitro and in vivo. The potential clinical benefit of this approach deserves further study.

BACKGROUND

Epithelial cell growth is normally under hormonal control. Hormones also affect the growth of many epithelial cancers, and this fact is used to modify tumor growth. Pancreatic epithelial cell growth is under the influence of gastrointestinal hormones. This article reviews experiments designed to determine the effect of gastrointestinal hormones on the growth of pancreatic adenocarcinoma.

METHODS

Eighty-eight articles were identified from a Medline search using the terms pancreatic adenocarcinoma and the individual names of gastrointestinal hormones. The experimental design and results of these studies are reviewed.

RESULTS

In general, somatostatin, vasoactive intestinal polypeptide, pancreatic polypeptide, and pancreastatin inhibit pancreatic adenocarcinoma growth. Cholecystokinin, secretin, bombesin, gastrin, EGF, TGF-alpha, insulin, and IGF-1 have a growth-promoting effect.

Spontaneous autoimmune gastritis in C3H/He mice: a new mouse model for gastric autoimmunity

Autoimmune gastritis is the underlying pathological lesion of pernicious anemia in humans. The lesion is characterized by a chronic inflammatory infiltrate in the gastric mucosa with loss of parietal and zymogenic cells. It is associated with circulating autoantibodies to the gastric H/K-ATPase, the enzyme responsible for acidification of gastric juice. Experimental models of autoimmune gastritis have previously been produced in mice after a variety of manipulations, including thymectomy. Here we report for the first time a spontaneous mouse model of autoimmune gastritis in C3H/He mice. The spontaneous gastritis is also accompanied by circulating autoantibodies to the gastric H/K-ATPase. The spontaneous mouse model should be useful for studies directed toward the immunopathogenesis and treatment of autoimmune gastritis.

CD4+ T cells, but not CD8+ T cells, are required for the development of experimental autoimmune gastritis

Murine autoimmune gastritis, induced by neonatal thymectomy, is characterized by a mononuclear infiltrate within the gastric mucosa, loss of parietal and zymogenic cells and circulating autoantibodies to the gastric H/K ATPase. The infiltrate contains both CD4+ and CD8+ T cells. Here we have investigated the roles of CD4+ and CD8+ T cells in the development of gastritis by in vivo treatment with depleting rat anti-CD4 and anti-CD8 monoclonal antibodies. Depletion of CD4+ T cells decreased the incidence of gastric mononuclear infiltrates from 63% (5/8), observed in normal rat immunoglobulin G (IgG)-injected mice, to 8% (1/12) and also abolished the production of antigastric autoantibodies. In contrast, depletion of CD8+ T cells did not reduce the incidence of gastritis. The absence of CD8+ T cells in the infiltrate of the stomach of anti-CD8(+)-treated mice was confirmed by immunocytochemistry. These results argue that neonatal thymectomy-induced autoimmune gastritis is mediated by CD4+ T cells and that CD8+ T cells do not play a significant role in the development of the gastric lesion.

CD4+CD25+ T Cells Inhibit Both the Induction and Effector Function of Autoreactive T Cells and Represent a Unique Lineage of Immunoregulatory Cells

Thymectomy of susceptible strains of mice on day 3 of life results in a spectrum of organ-specific autoimmunity that can be prevented by reconstitution of the thymectomized animals early in life with normal adult lymphocytes. The effectors and suppressors of autoimmunity in this model have been convincingly shown to be CD4+ T cells. It has been demonstrated recently that the regulatory CD4+ T cells that prevent disease coexpress CD25. We have further characterized the population of CD4+CD25+ immunoregulatory cells and demonstrated that they can suppress not only the induction of disease post-thymectomy, but can also efficiently suppress disease induced by cloned autoantigen-specific effector cells. Furthermore, the CD4+CD25+ T cells appear to be members of a unique lineage of regulatory T cells, as the induction of CD25 expression on a monospecific population of T cells derived from TCR transgenic SCID mice did not result in suppression of post-thymectomy autoimmunity. In addition, the TCR transgenic SCID mice were highly susceptible to autoimmune disease induced by the cloned line of autoantigen-specific effectors, while normal mice were relatively resistant. The capacity of the cloned line to transfer disease to nu/nu recipients could be inhibited by normal spleen cell populations containing CD4+CD25+ cells and by purified CD4+CD25+ cells. Although the target Ag(s) and mechanism of action of the CD4+CD25+ T cells remain to be determined, it is likely that they also play an important role in modulating other autoimmune diseases that are mediated by activation of “ignorant” self-reactive T cells present in the normal peripheral lymphocyte pool.

The thymus contains a high frequency of cells that prevent autoimmune diabetes on transfer into prediabetic recipients

Rats of the PVG.RT1u strain develop autoimmune diabetes when thymectomized at 6 wk of age and are rendered relatively lymphopenic by a cumulative dose of 1,000 rads 137Cs gamma-irradiation given in four split doses. Previous studies have shown that the disease is prevented by the intravenous injection of 5 x 10(6) CD4+ CD45RC-TCR alpha beta+ RT6+ peripheral T cells from normal syngeneic donors. These cells have a memory phenotype and are presumably primed to some extrathymic antigen. However, we now report that the CD4+ CD8- population of mature thymocytes is a very potent source of cells, with the capacity to prevent diabetes in our lymphopenic animals. As few as 6 x 10(5) of these cells protect approximately 50% of recipients and the level of protection increases with cell dose. It appears that one characteristic of the intrathymic selection of the T cell repertoire is the generation of cells that regulate the autoimmune potential of peripheral T cells that have been neither clonally deleted intrathymically nor rendered irreversibly anergic in the periphery.

Interferon-gamma is required during the initiation of an organ-specific autoimmune disease

Autoimmune gastritis induced by neonatal thymectomy of mice is a CD4+ T cell-mediated organ-specific autoimmune disease. The characteristic features of autoimmune gastritis, which include a mononuclear infiltrate within the gastric mucosa, loss of parietal and chief cells and circulating autoantibodies to the gastric H+/K+ ATPase, appear 6-10 weeks after thymectomy. Here we have assessed the role of interferon-gamma (IFN-gamma) in the pathogenesis of the gastric lesion. Splenic T cells derived from mice with gastritis produced three- to tenfold more IFN-gamma than T cells from normal animals after stimulation with anti-CD3 antibodies. Treatment of neonatally thymectomized mice at weekly intervals for 6 or 12 weeks with a neutralizing rat monoclonal antibody to mouse IFN-gamma abolished the production of anti-gastric autoantibodies and decreased the incidence of gastric mononuclear infiltrates from the 69% observed in normal rat immunoglobulin (Ig)-injected mice to 16%. Further, in mice treated with only a single dose of anti-IFN-gamma immediately after thymectomy at 3 days after birth, the incidence of autoimmune gastritis was 1/19 compared to 8/19 in normal rat Ig-injected mice. Prevention of autoimmunity by neutralization of IFN-gamma several weeks prior to the detection of a pathological lesion strongly suggests that IFN-gamma plays an essential role in the initiation of the gastric autoimmune response.