Multidose streptozotocin induction of diabetes in BALB/cBy mice induces a T cell proliferation defect in thymocytes which is reversible by interleukin-4

Recombinant Lactococcus lactis Carrying IL-4 and IL-10 Coding Vectors Protects against Type 1 Diabetes in NOD Mice and Attenuates Insulitis in the STZ-Induced Model

Type 1 diabetes (T1D) is an autoimmune disease that culminates in beta cell destruction in the pancreas and, subsequently, deficiency in insulin production. Cytokines play a crucial role in the development of diabetes, orchestrating the recruitment and action of immune cells, to not only destroy insulin-producing cells but also preserve them. Therefore, the aim of this study was to investigate the effect of orally administered Lactococcus lactis MG1363 FnBPA+ strains carrying plasmids encoding IL-4 and IL-10 in the streptozotocin- (STZ-) induced diabetes model and in nonobese diabetic (NOD) mice. The STZ-induced mice that were treated with combined bacterial strains carrying plasmids encoding IL-4 and IL-10 showed lower incidence of diabetes and more preserved pancreatic islets than the mice that received the individual bacterial strains. Combined administration of L. lactis MG1363 FnBPA+ (pValac::dts::IL-4) and L. lactis MG1363 FnBPA+ (pValac::IL-10) resulted in protection against diabetes in NOD mice. It was shown that the combined treatment with recombinant bacterial by oral route prevented hyperglycemia and reduced the pancreatic islets-destruction in NOD mice. In addition, increased levels of IL-4 and IL-10 in serum and pancreatic tissue revealed a systemic effect of the treatment and also favored an anti-inflammatory microenvironment. Reduced concentrations of IL-12 in pancreas were essential to the regulation of inflammation, resulting in no incidence of diabetes in treated NOD mice. Normal levels of intestinal sIgA after long-term treatment with the L. lactis strains carrying plasmids encoding IL-4 and IL-10 indicate the development of oral tolerance and corroborate the use of this potent tool of mucosal delivery. For the first time, L. lactis MG1363 FnBPA+ strains carrying eukaryotic expression vectors encoding IL-4 and IL-10 are tested in STZ-induced and NOD mouse models. Therefore, our study demonstrates this innovative strategy provides immunomodulatory potential for further investigations in T1D and other autoimmune diseases.

Erythropoietin Protects Against Cognitive Impairment and Hippocampal Neurodegeneration in Diabetic Mice

Administration of erythropoietin (EPO) is neuroprotective against a variety of experimentally-induced neurological disorders. The aim was to determine if EPO protects against hippocampal neurodegeneration as well as impairment of cognition and motor performance, associated with long-term diabetes. BALB/c mice were randomly allocated between control, diabetic and EPO-treated diabetic groups. EPO-treated diabetic mice were administered EPO 0.05 U/kg/day i.p. three times/week for 10 weeks. Cognition was assessed by Morris water maze. Brain samples were processed for light microscopic evaluation of hippocampus. Controls showed gradual improvement of cognitive performance in water maze when comparing latency (p < 0.01) and distance swum to reach the platform (p = 0.001). There was a similar trend for improvement in EPO-treated diabetics (p < 0.001). Latency did not improve in diabetic animals indicating lack of learning (p = 0.79). In probe trials, controls and EPO-treated diabetics spent more time in the training quadrant than expected by chance (p < 0.001). Diabetics did not show memory recall behavior; performance was significantly worse than expected by chance (p = 0.023). In diabetics, there was neurodegeneration in hippocampus and reduction in number of granule cells (p < 0.01) in the dentate gyrus. EPO treatment improved these neurodegenerative changes and preserved numbers of granule cells (p < 0.1, compared to controls). Erythropoietin treatment is protective against cognitive deficits and hippocampal neurodegeneration in diabetic mice.

Effectiveness of Antihyperglycemic Effect of Momordica charantia: Implication of T-Cell Cytokines

BACKGROUND/OBJECTIVE

We investigate the effect of antidiabetic Momordica charantia fruit juice on T cells' differentiation, through plasmatic cytokine quantification in type 1 diabetic rats (T1D).

METHODS

Male Wistar rats were rendered diabetic by the injection of five low doses of streptozotocin. Then, animals were treated with Momordica charantia fruit juice for 28 consecutive days. Plasmatic levels of Th1 interleukin- (IL-) 02 and interferon- (IFN-) γ, Th2 (IL-4), and regulatory (IL-10) cytokines were determined in rats.

RESULTS

We observed that fruit juice induced a significant decrease in blood glucose of T1D rats. Besides, the concentrations of IL-2 and IFN-γ significantly increased while those of IL-4 and IL-10 diminished in diabetic rats compared to control animals. Interestingly, after treatment with Momordica charantia fruit juice, IL-4 and IL-10 levels significantly increased in diabetic rats, while IL-2 and IFN-γ concentrations decreased, suggesting a Th2 phenotype in these animals. Phytochemical analysis of the fruit juice revealed the presence of tannins, flavonoids, and coumarins, compounds which possess antioxidant activity.

CONCLUSION

This study shows that Momordica charantia fruit juice, by lowering the hyperglycemia, induced a shift of proinflammatory Th1 phenotype in T1D rats towards a favorable anti-inflammatory Th2 status. These effects might be due to the presence of antioxidant compounds in the juice and confirms the use of this plant in the treatment of autoimmune type 1 diabetes.

Evidence of Immunosuppressive and Th2 Immune Polarizing Effects of Antidiabetic Momordica charantia Fruit Juice

The mechanism of action of the antidiabetic capacity of Momordica charantia is still under investigation. Here, we assessed phytochemical compositions, antioxidant activity, and effects of total and filtered fruit and leafy stem juices of Momordica charantia on human T cell proliferation and differentiation through quantification of Th1/Th2 cytokines. In the absence of stimulation, total fruit and leafy stem juices induced significant T cell proliferation. Under PHA stimulation, both juices potentiated plant-induced T cell proliferation. However, the filtered fruit and leafy stem juices significantly inhibited PHA-stimulated T cell proliferation, while neither juice influenced T cell proliferation. Moreover, total and filtered fruit juice increased IL-4 secretion, while total and filtered leafy stem juice enhanced IFN-γ production. Phytochemical screening revealed the presence of tannins, flavonoids, anthocyans, steroids, and triterpenoids in both juices. Alkaloids, quinone derivatives, cardenolides, and cyanogenic derivatives were undetectable. The saponins present in total juices were undetectable after filtration. Moreover, both juices had appreciable antioxidant capacity. Our study supports the type 1 antidiabetic effect of filtered fruit juice of M. charantia which may be related to its immunosuppressive and T-helper 2 cell inducing capacities. Due to their immune-stimulatory activities and their ability to increase T-helper 1 cell cytokines, total fruit and leafy stem juices may serve in the treatment of immunodeficiency and certain infections.

Modulation of immune cells and Th1/Th2 cytokines in insulin-treated type 2 diabetes mellitus

BACKGROUND

The role of the immune system in insulin resistance associated with type 2 diabetes has been suggested.

OBJECTIVES

We assessed the profile of Th1/Th2 cytokines along with the frequencies of immune cells in insulin-treated type 2 diabetic patients (T2DP).

METHODS

45 T2D patients and 43 age-matched healthy subjects were selected. Serum concentrations of T-helper type 1 (Th1) and Th2 cytokines and the frequencies of innate and adaptive immunity cells were assessed.

RESULTS

T2DP were hyperglycemic and showed high level of insulin, normal levels of triglycerides and total-cholesterol and without any change in HDL-cholesterol.Compared to healthy subjects, T2DP exhibited significant decreased frequencies of neutrophils, without any change in monocytes, eosinophils and natural killer cells. The percentages of total lymphocytes (CD3+) and CD8+-T-cells decreased whereas those of regulatory T-cells increased without any change in CD4+ T-cells in T2DP. Interestingly, the frequencies of effector CD4+-T and B-cells increased in T2DP. Serum concentrations of IL-2, IFN-γ and IL-4 decreased while IL-10 significantly enhanced in T2DP, suggesting a differentiation of CD4+T helper cells towards IL-10-producing-Teff-cells in these patients.

CONCLUSION

Insulin-treated type 2 diabetes is associated with anti-inflammatory profile consistent with differentiation of CD4+-Th-cells towards IL-10-producing-Teff-cells, concomitant with increased frequencies of Treg and B-cells, and this may probably offer prevention against certain infections or autoimmune/inflammatory diseases.

Identification of Candidate Tolerogenic CD8(+) T Cell Epitopes for Therapy of Type 1 Diabetes in the NOD Mouse Model

Type 1 diabetes is an autoimmune disease in which insulin-producing pancreatic islet β cells are the target of self-reactive B and T cells. T cells reactive with epitopes derived from insulin and/or IGRP are critical for the initiation and maintenance of disease, but T cells reactive with other islet antigens likely have an essential role in disease progression. We sought to identify candidate CD8(+) T cell epitopes that are pathogenic in type 1 diabetes. Proteins that elicit autoantibodies in human type 1 diabetes were analyzed by predictive algorithms for candidate epitopes. Using several different tolerizing regimes using synthetic peptides, two new predicted tolerogenic CD8(+) T cell epitopes were identified in the murine homolog of the major human islet autoantigen zinc transporter ZnT8 (aa 158-166 and 282-290) and one in a non-β cell protein, dopamine β-hydroxylase (aa 233-241). Tolerizing vaccination of NOD mice with a cDNA plasmid expressing full-length proinsulin prevented diabetes, whereas plasmids encoding ZnT8 and DβH did not. However, tolerizing vaccination of NOD mice with the proinsulin plasmid in combination with plasmids expressing ZnT8 and DβH decreased insulitis and enhanced prevention of disease compared to vaccination with the plasmid encoding proinsulin alone.

Bacille Calmette-Guérin/DNAhsp65 prime-boost is protective against diabetes in non-obese diabetic mice but not in the streptozotocin model of type 1 diabetes

Type I diabetes is a disease caused by autoimmune destruction of the beta cells in the pancreas that leads to a deficiency in insulin production. The aim of this study was to evaluate the prophylactic potential of a prime-boost strategy involving bacille Calmette-Guérin (BCG) and the pVAXhsp65 vaccine (BCG/DNAhsp65) in diabetes induced by streptozotocin (STZ) in C57BL/6 mice and also in spontaneous type 1 diabetes in non-obese diabetic (NOD) mice. BCG/DNAhsp65 vaccination in NOD mice determined weight gain, protection against hyperglycaemia, decreased islet inflammation, higher levels of cytokine production by the spleen and a reduced number of regulatory T cells in the spleen compared with non-immunized NOD mice. In the STZ model, however, there was no significant difference in the clinical parameters. Although this vaccination strategy did not protect mice in the STZ model, it was very effective in NOD mice. This is the first report demonstrating that a prime-boost strategy could be explored as an immunomodulatory procedure in autoimmune diseases.

Effect of selenium on connexin expression, angiogenesis, and antioxidant status in diabetic wound healing

This study was done to analyze the effect of selenium on antioxidant status and expression of different connexins in diabetic wound healing. The levels of vascular endothelial growth factor, superoxide dismutase, lipid peroxide, and connexins were analyzed in wound tissues taken from diabetic and non-diabetic mice before and after sodium selenite administration. The mRNA transcript levels of Cx 26, 30.3, 31, 31.1, and 43 were significantly elevated in diabetic wounds as compared to the non-diabetic wounds. After selenium administration, the expression of connexins along with serum glucose decreases more significantly in diabetic wounds as compared to non-diabetic wounds. In diabetic wounds, the low levels of vascular endothelial growth factor and extracellular superoxide dismutase were restored to normal level following selenium administration. The lipid peroxidation decreased significantly in diabetic mice post-selenium administration. The histopathological analysis revealed that administration of selenium improves angiogenesis at the wound site. The results of this study demonstrate that selenium, acting as an essential component of the antioxidant system, normalizes the antioxidant status, and as an insulin mimetic compound, downregulates connexin expressions and induces angiogenesis. Together, these effects of selenium accelerate wound healing in diabetic conditions.

Innovative Immune-Based Therapeutic Approaches for the Treatment of Type 1 Diabetes Mellitus

Type 1 diabetes mellitus is an autoimmune disease caused by a culmination of noxious processes of autoimmunity composed of various components of the innate and adaptive immune systems. Current treatment of type 1 diabetes focuses on restraining the endocrine disease without affecting the autoimmune process that underlies it. Prevention of this disease requires immune modulation and early intervention. New therapeutic approaches can be classified on the basis of the immunological arm targeted, that is, T-cell immune modulation (using cytokines, anti-CD3 monoclonal antibodies, and peptide MHC class II dimers), innate immune system modulation (using alpha-galactosylceramide or peptide 277), or specific antigen vaccination (glutamic acid decarboxylase and insulin). Here we review the most promising therapies developed based on these targets and emphasize those that have reached human phase clinical investigation.

AAV8-mediated gene transfer of interleukin-4 to endogenous beta-cells prevents the onset of diabetes in NOD mice

We have demonstrated the ability to deliver and express genes specifically in beta-cells for at least 6 months, using a murine insulin promoter (mIP) in a double-stranded, self-complementary AAV vector (dsAAV8-mIP). In this study, we evaluated the effects of dsAAV8-mIP-mediated delivery of interleukin 4 (mIL-4) to endogenous beta-cells in nonobese diabetic (NOD) mice. In 4-week-old NOD mice, the extent of gene transfer and expression in endogenous beta-cells after ip delivery of dsAAV8-mIP-enhanced green fluorescent protein (eGFP) was comparable to normal BALB/C mice. Further, after IP delivery of dsAAV8-mIP-IL4, expression of mIL-4 was detected in islets isolated from the treated mice and cultured. AAV8-mIP-mediated gene expression of mIL-4 in endogenous beta- cells of 4- and 8-week-old NOD mice prevented the onset of hyperglycemia in NOD mice and reduced the severity of insulitis. Moreover, expression of mIL-4 also maintained the level of CD4(+)CD25(+)FoxP3(+) cells, and adoptive transfer of splenocytes from nondiabetic dsAAV8-mIP-IL-4 mice to NODscid mice was able to block the diabetes induced by splenocytes co-adoptively transferred from nondiabetic dsAAV-mIP-eGFP mice. Taken together, these results demonstrate that local expression of mIL-4 in islets prevents islet destruction and blocks autoimmunity, partly through regulation of T-cell function.

Modulation of adipokines and cytokines in gestational diabetes and macrosomia

CONTEXT/OBJECTIVE

Not much is known about the implication of adipokines and different cytokines in gestational diabetes mellitus (GDM) and macrosomia. The purpose of this study was to assess the profile of these hormones and cytokines in macrosomic babies, born to gestational diabetic women.

DESIGN/SUBJECTS

A total of 59 women (age, 19-42 yr) suffering from GDM with their macrosomic babies (4.35 +/- 0.06 kg) and 60 healthy age-matched pregnant women and their newborns (3.22 +/- 0.08 kg) were selected.

METHODS

Serum adipokines (adiponectin and leptin) were quantified using an obesity-related multiple ELISA microarray kit. The concentrations of serum cytokines were determined by ELISA.

RESULTS

Serum adiponectin levels were decreased, whereas the concentrations of leptin, inflammatory cytokines, such as IL-6 and TNF-alpha, were significantly increased in gestational diabetic mothers compared with control women. The levels of these adipocytokines were diminished in macrosomic babies in comparison with their age-matched control newborns. Serum concentrations of T helper type 1 (Th1) cytokines (IL-2 and interferon-gamma) were decreased, whereas IL-10 levels were significantly enhanced in gestational diabetic mothers compared with control women. Macrosomic children exhibited high levels of Th1 cytokines and low levels of IL-10 compared with control infants. Serum IL-4 levels were not altered between gestational diabetic mothers and control mothers or the macrosomic babies and newborn control babies.

CONCLUSIONS

GDM is linked to the down-regulation of adiponectin along with Th1 cytokines and up-regulation of leptin and inflammatory cytokines. Macrosomia was associated with the up-regulation of Th1 cytokines and the down-regulation of the obesity-related agents (IL-6 and TNF-alpha, leptin, and adiponectin).

Peroxisome proliferator-activated receptor alpha deficiency increases the risk of maternal abortion and neonatal mortality in murine pregnancy with or without diabetes mellitus: Modulation of T cell differentiation

We assessed the implication of peroxisome proliferator-activated receptor (PPAR) alpha deficiency in pregnancy outcome and neonatal survival and in the modulation of T cell differentiation in murine diabetic pregnancy and their offspring. Pregnant wild-type (WT) and PPAR alpha-null mice of C57BL/6J genetic background were rendered diabetic by five low doses of streptozotocin. We observed that, in the absence of diabetes, PPAR alpha deficiency resulted in an increase in abortion rate, i.e. 0% in WT mice vs. 20% in PPAR alpha-null mice [odds ratio (OR) = 14.33; P = 0.013]. Under diabetic conditions, the abortion rate was enhanced, i.e. 8.3% in WT mice vs. 50% in PPAR alpha-null mice (OR = 4.28; P = 0.011). In the pups born to diabetic dams, the offspring mortality, due to the absence of PPAR alpha, was enhanced, i.e. 27.7% in WT mice vs. 78.9% in PPAR alpha-null animals (OR = 11.48; P < 0.001). Moreover, we observed that T helper (Th) 1/Th2 balance was shifted to a pregnancy protecting Th2 phenotype in WT diabetic dams and to a noxious Th1 phenotype in PPAR alpha-null mice with diabetic pregnancy. Furthermore, offspring born to diabetic WT dams were hyperinsulinemic and hyperglycemic, and they exhibited up-regulated profile of Th2 cytokines, whereas those born to diabetic PPAR alpha-null dams were hypoinsulinemic and hyperglycemic, and they showed down-regulated profile of Th2 cytokines. However, IFN-gamma, a Th1 cytokine, was up-regulated in the offspring of both diabetic WT and PPAR alpha-null dams. Altogether, our results suggest that PPAR alpha deficiency in mice may be implicated in the increase in maternal abortion, neonatal mortality, and T cell differentiation.

Multidose streptozotocin induction of diabetes in BALB/c mice induces a dominant oxidative macrophage and a conversion of TH1 to TH2 phenotypes during disease progression

Macrophages (Mp) are implicated in both early and late phases in type 1 diabetes development. Recent study has suggested that a balance between reductive Mp (RMp) and oxidative Mp (OMp) is possible to regulate T_H1/T_H2 balance. The aim of this study is to investigate the redox status of peritoneal Mp and its cytokine profile during the development of autoimmune diabetes induced by multiple low-dose streptozotocin in BALB/c mice. Meanwhile, the polarization of T_H1/T_H2 of splenocytes or thymocytes was also examined. We found that peritoneal Mp appeared as an “incomplete” OMp phenotype with decreased icGSH along with disease progression. The OMp showed reduced TNF-α, IL-12, and NO production as well as defective phagocytosis activity compared to nondiabetic controls; however, there was no significant difference with IL-6 production. On the other hand, the levels of IFN-γ or IL-4 of splenocytes in diabetic mice were significantly higher compared to the control mice. The ratio of IFN-γ to IL-4 was also higher at the early stage of diabetes and then declined several weeks later after the occurrence of diabetes, suggesting a pathogenetic T_H1 phenotype from the beginning gradually to a tendency of T_H2 during the development of diabetes. Our results implied that likely OMp may be relevant in the development of type 1 diabetes; however, it is not likely the only factor regulating the T_H1_H/T_H2 balance in MLD-STZ-induced diabetic mice.

N-3 Fatty acids modulate antioxidant status in diabetic rats and their macrosomic offspring

OBJECTIVE

We investigated the role of dietary n-3 polyunsaturated fatty acids (n-3 PUFA) in the modulation of total antioxidant status in streptozotocin (STZ)-induced diabetic rats and their macrosomic offspring.

DESIGN

Female wistar rats, fed on control diet or n-3 PUFA diet, were rendered diabetic by administration of five mild doses of STZ on day 5 and were killed on days 12 and 21 of gestation. The macrosomic (MAC) pups were killed at the age of 60 and 90 days.

MEASUREMENTS

Lipid peroxidation was measured as the concentrations of plasma thiobarbituric acid reactive substances (TBARS), and the total antioxidant status was determined by measuring (i) plasma oxygen radical absorbance capacity (ORAC), (ii) plasma vitamin A, E and C concentrations, and (iii) antioxidant enzymes activities in erythrocytes. The plasma lipid concentrations and fatty acid composition were also determined.

RESULTS

Diabetes increased plasma triglyceride and cholesterol concentrations, whereas macrosomia was associated with enhanced plasma cholesterol and triglyceride levels, which diminished by feeding n-3 PUFA diet. N-3 PUFA diet also reduced increased plasma TBARS and corrected the decreased ORAC values in diabetic rats and their macrosomic offspring. EPAX diet increased the diminished vitamin A levels in diabetic mothers and vitamin C concentrations in macrosomic pups. Also, this diet improved the decreased erythrocyte superoxide dismutase and glutathione peroxidase activities in diabetic and macrosomic animals.

CONCLUSION

Diabetes and macrosomia were associated with altered lipid metabolism, antioxidant enzyme activities and vitamin concentrations. N-3 PUFA diet improved hyperlipidemia and restored antioxidant status in diabetic dams and MAC offspring.

Protective effects of a calcium channel blocker on apoptosis in thymus of neonatal STZ-diabetic rats

Streptozotocin (STZ) is known to induce insulin-dependent diabetes in experimental animals. In STZ-induced diabetes, atrophy of the thymus is caused by elevated intracellular calcium levels leading to apoptosis. Hyperglycemia is known to result in a decrease in numbers of T cells in the thymus and circulation. Intracellular calcium levels increase in diabetic animals after induction by STZ. Hyperglycemia inhibits Ca2+-ATPase and increases intracellular calcium levels. We have investigated apoptosis in thymus tissue of neonatal STZ (n-STZ)-diabetic rats and the effects of isradipine as a calcium channel blocker (CCB) on apoptosis. Five groups of newborn Wistar rats were used. On the second day after birth, 100 mg/kg STZ was given i.p. to the first two groups. The first group was n-STZ diabetic. To the second group, starting from the 12th week, 5 mg/kg/day isradipine (i.p) was given for 6 weeks. To the third group, the same dose of isradipine was given on the second day, followed by STZ treatment. The fourth group was non-diabetic and treated with 5 mg/kg/day isradipine for six weeks. The fifth group consisted of non-diabetic rats. To the sixth group, dexamethasone (5 mg/kg i.p.) was given to adult rats. For detection of apoptotic cells in paraffin-embedded thymus sections, the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labelling (TUNEL) assay was used. The DNA ladder method was performed for analysis of DNA fragmentation. In the isradipine-treated non-diabetic group, typical apoptotic banding patterns were found, whereas thick bands between 123 and 246 bp length were found in the n-STZ- and n-STZ+isradipine-treated groups. More apoptotic cells were observed in the thymus of isradipine-treated, n-STZ-treated and n-STZ+isradipine-treated groups when compared with the non-diabetic control and isradipine+n-STZ-treated groups. In conclusion, we observed that long-term STZ diabetes results in apoptosis in the thymus. We also found that isradipine administered before STZ has protective effects against apoptosis, whereas isradipine alone induces apoptosis.

Immune modulation for prevention of type 1 diabetes mellitus

Prevention of type 1 diabetes mellitus requires early intervention in the autoimmune process directed against beta cells of the pancreatic islets of Langerhans. This autoimmune inflammatory process is thought to be caused by the effect of Th1 cells and their secreted cytokines (e.g. interferon) and to be suppressed by Th2-secreted anti-inflammatory cytokines (e.g. IL-4, IL-10). Various methods aimed specifically at halting or modulating this response have been attempted. An alternative method is the re-induction of tolerance towards the putative self antigen that causes the disease. Proposed antigens such as insulin, glutamic acid decarboxilase (GAD) and the heat shock protein 60 (Hsp60)-derived peptide 277 have been used successfully in murine diabetes models and in initial clinical trials in early diabetes patients. Here, we review the results of these trials.

Mast cell changes in experimental diabetes: focus on attenuation of allergic events

The prevalence of atopic diseases and diabetes is increasing worldwide though the concurrence of these pathologies in individual patients is found less frequent than it would be predicted. Moreover, co-existence of diabetes and allergy is generally marked by attenuation of their respective symptoms, and effective treatment of one disease exacerbates the other. This review gives an update of the state-of-the-art concerning the intercurrence of allergy and diabetes, particularly focusing on the consequences to the allergen-evoked vascular and cellular changes. It is proposed that the reduction in mast cell numbers and reactivity may be a pivotal mechanism behind the mutual exclusion phenomenon.

Brazilin augments cellular immunity in multiple low dose streptozotocin (MLD-STZ) induced type I diabetic mice

Brazilin, an active principle of Caesalprenia sappan, was examined for its immunopotentiating effects in multiple low dose streptozotocin (MLD-STZ) induced type diabetic mice. Brazilin was intraperitoneally administered for 5 consecutive days to MLD-STZ induced type I diabetic mice. Delayed type hypersensitivity, Con A-induced proliferation of splenocytes and mixed lymphocyte reaction, which had been decreased in diabetic mice, were significantly recovered by the administration of brazilin. Brazilin increased IL-2 production without affecting suppressor cell activity. Con A-induced and IL-2-induced expression of high affinity IL-2 receptors were also enhanced by brazilin. These results indicate that brazilin augments cellular immune responses, which are suppressed in the MLD-STZ induced type I diabetic mice, by increasing IL-2 production and responsiveness of immune cells to IL-2.

Mice bearing late-stage tumors have normal functional systemic T cell responses in vitro and in vivo

Immune suppression in tumor-bearing hosts is considered to be one factor causally associated with the growth of antigenic tumors. Support for this hypothesis has come from reports that spleen T cells in tumor-bearing mice are deficient in either priming or effector phase functions. We have reexamined this hypothesis in detail using multiple murine tumor models, including transplantable adenocarcinoma, melanoma, sarcoma, and thymoma, and also a transgenic model of spontaneous breast carcinoma. In both in vitro and in vivo assays of T cell function (proliferation, cytokine production, induction of CD8+ alloreactive CTL, and development of anti-keyhole limpet hemocyanin CD4+ T cells, rejection of allogeneic or syngeneic regressor tumors, respectively) we show that mice bearing sizable tumor burdens are not systemically suppressed and do not have diminished T cell functions. Therefore, if immune suppression is a causal function in the growth of antigenic tumor, the basis for escape from immune destruction is likely to be dependent upon tumor-induced T cell dysfunction at the site of tumor growth.

Pancreatic IL-4 Expression Results in Islet-Reactive Th2 Cells That Inhibit Diabetogenic Lymphocytes in the Nonobese Diabetic Mouse

When immunological tolerance breaks down, autoimmune destruction of insulin-producing β cells in the pancreas can cause insulin-dependent diabetes mellitus. We previously showed that transgenic nonobese diabetic (NOD) mice expressing IL-4 in the pancreas (NOD-IL-4 mice) were protected from insulitis and diabetes. Here we have characterized the avoidance of pathological autoimmunity in these mice. The absence of disease did not result from a lack of T cell priming, because T cells responding to dominant islet Ags were present. These islet Ag-specific T cells displayed a Th2 phenotype, indicating that Th2 responses could account for the observed tolerance. Interestingly, islet Ag-specific Th1 T cells were present and found to be functional, because neutralization of the Th2 effector cytokines IL-4 and IL-10 resulted in diabetes. Histological examination revealed that NOD-IL-4 splenocytes inhibited diabetogenic T cells in cotransfer experiments by limiting insulitis and delaying diabetes. Neutralization of IL-4 in this system abrogated the ability of NOD-IL-4 splenocytes to delay the onset of diabetes. These results indicate that IL-4 expressed in the islets does not prevent the generation of pathogenic islet responses but induces islet Ag-specific Th2 T cells that block the action of diabetogenic T cells in the pancreas.