Interleukin 2 and soluble interleukin 2-receptor secretion defect in vitro in newly diagnosed type I diabetic patients

Evolving Antibody Therapies for the Treatment of Type 1 Diabetes

Type 1 diabetes (T1D) is widely considered to be a T cell driven autoimmune disease resulting in reduced insulin production due to dysfunction/destruction of pancreatic β cells. Currently, there continues to be a need for immunotherapies that selectively reestablish persistent β cell-specific self-tolerance for the prevention and remission of T1D in the clinic. The utilization of monoclonal antibodies (mAb) is one strategy to target specific immune cell populations inducing autoimmune-driven pathology. Several mAb have proven to be clinically safe and exhibit varying degrees of efficacy in modulating autoimmunity, including T1D. Traditionally, mAb therapies have been used to deplete a targeted cell population regardless of antigenic specificity. However, this treatment strategy can prove detrimental resulting in the loss of acquired protective immunity. Nondepleting mAb have also been applied to modulate the function of immune effector cells. Recent studies have begun to define novel mechanisms associated with mAb-based immunotherapy that alter the function of targeted effector cell pools. These results suggest short course mAb therapies may have persistent effects for regaining and maintaining self-tolerance. Furthermore, the flexibility to manipulate mAb properties permits the development of novel strategies to target multiple antigens and/or deliver therapeutic drugs by a single mAb molecule. Here, we discuss current and potential future therapeutic mAb treatment strategies for T1D, and T cell-mediated autoimmunity.

The Role of T Cell Receptor Signaling in the Development of Type 1 Diabetes

T cell receptor (TCR) signaling influences multiple aspects of CD4⁺ and CD8⁺ T cell immunobiology including thymic development, peripheral homeostasis, effector subset differentiation/function, and memory formation. Additional T cell signaling cues triggered by co-stimulatory molecules and cytokines also affect TCR signaling duration, as well as accessory pathways that further shape a T cell response. Type 1 diabetes (T1D) is a T cell-driven autoimmune disease targeting the insulin producing β cells in the pancreas. Evidence indicates that dysregulated TCR signaling events in T1D impact the efficacy of central and peripheral tolerance-inducing mechanisms. In this review, we will discuss how the strength and nature of TCR signaling events influence the development of self-reactive T cells and drive the progression of T1D through effects on T cell gene expression, lineage commitment, and maintenance of pathogenic anti-self T cell effector function.

IL-2 Inhibition of Th17 Generation Rather Than Induction of Treg Cells Is Impaired in Primary Sjögren's Syndrome Patients

Objective

To investigate the role of IL-2 in the balance of Th17 and Tregs and elucidate the underlying mechanisms of enhanced Th17 differentiation in primary Sjögren’s syndrome (pSS) patients.

Methods

This study involved 31 pSS patients, 7 Sicca patients, and 31 healthy subjects. Th17 and Treg cells were determined by flow cytometry, and IL-17A was detected by immunohistochemistry. IL-2 and IL-6 levels were assessed by ELISA and qPCR. p-STAT5 and p-STAT3 in salivary glands (SGs) were evaluated by immunohistochemistry and flow cytometry. The binding of STAT5 and STAT3 to the Il17a gene locus was measured by chromatin immunoprecipitation.

Results

We found that the percentage of Th17 cells was increased in the periphery and SG of pSS patients when compared with healthy subjects, but the Treg cells was unchanged. Meanwhile, the IL-2 level was reduced, and the IL-6 and IL-17A level was increased in the plasma of pSS patients. The ratio of IL-2 and IL-6 level was also decreased and IL-2 level was negatively correlated with the level of IL-17A. The expression of Il6 and Il17a mRNA was significantly increased, whereas Foxp3, Tgfb1, Tnfa, and Ifng mRNA were comparable. Furthermore, the level of STAT5 phosphorylation (p-STAT5) was reduced and p-STAT3 was enhanced in the SGs and in peripheral CD4⁺ T cells of pSS patients. In vitro IL-2 treatment-induced STAT5 competed with STAT3 binding in human Il17a locus, leading to decreased Th17 differentiation, which was associated with the reduced transcription activation marker H3K4me3.

Conclusion

Our findings demonstrated a Treg-independent upregulation of Th17 generation in pSS, which is likely due to a lack of IL-2-mediated suppression of Th17 differentiation. This study identified a novel mechanism of IL-2-mediated immune suppression in pSS.

Type 1 Diabetes: A Chronic Anti-Self-Inflammatory Response

Inflammation is typically induced in response to a microbial infection. The release of proinflammatory cytokines enhances the stimulatory capacity of antigen-presenting cells, as well as recruits adaptive and innate immune effectors to the site of infection. Once the microbe is cleared, inflammation is resolved by various mechanisms to avoid unnecessary tissue damage. Autoimmunity arises when aberrant immune responses target self-tissues causing inflammation. In type 1 diabetes (T1D), T cells attack the insulin producing β cells in the pancreatic islets. Genetic and environmental factors increase T1D risk by in part altering central and peripheral tolerance inducing events. This results in the development and expansion of β cell-specific effector T cells (Teff) which mediate islet inflammation. Unlike protective immunity where inflammation is terminated, autoimmunity is sustained by chronic inflammation. In this review, we will highlight the key events which initiate and sustain T cell-driven pancreatic islet inflammation in nonobese diabetic mice and in human T1D. Specifically, we will discuss: (i) dysregulation of thymic selection events, (ii) the role of intrinsic and extrinsic factors that enhance the expansion and pathogenicity of Teff, (iii) defects which impair homeostasis and suppressor activity of FoxP3-expressing regulatory T cells, and (iv) properties of β cells which contribute to islet inflammation.

Serum levels of soluble IL-2R, CD4 and CD8 in bronChial asthma

The aim of the present study was to compare serum levels of soluble forms of interleukin-2 receptor, CD4 and CD8, released by lymphocytes during activation of the immune system, in patients with allergic bronchial asthma, with those in healthy subjects. Significantly higher levels of soluble IL-2R and soluble CD4 were found in patients with asthma compared with the control group. In contrast, lower levels of soluble CD8 values were found in patients with asthma compared to the control group. Significant correlations were found for both sIL-2R and sCD4 and these two molecules, with lung function measured as bronchial responsiveness to inhaled methacholine. These results strengthen previous suggestions that in allergic bronchial asthma, activation of T cells plays a significant role in the disease pathogenesis.

Biological significance of soluble IL-2 receptor

A NUMBER of receptors for growth factors and differentiation antigens have been found to be secreted or released by cells. Following mononuclear cell (MNC) activation and interleukin-2 receptor (IL-2R) expression, a soluble form of the Alpha;-chain of IL-2R (sIL-2R) is released. The sIL-2R has been shown to be present in the culture supernatants of activated MNCs as well as in normal sera and, in higher amounts, in sera from subjects affected by several diseases including neoplastic, infectious and autoimmune ones, and in sera from transplanted patients suffering allograft rejection. The blood sIL-2R levels depend on the number of producing cells and the number of molecules per cell, so that sIL-2R blood values may represent an index of the number and the functional state of producing cells, both normal and neoplastic. Thus, monitoring of the immune system, mostly T-cells and haematological malignancies might be targets for the measurement of sIL-2R. Since many conditions may influence sIL-2R production, little diagnostic use may result from these measurements. However, since blood sIL-2R levels may correlate with disease progression and/or response to therapy, their measurement may be a useful index of activity and extent of disease. The precise biological role of the soluble form of the IL-2R is still a matter of debate. However, we know that increased sIL-2R levels may be observed in association with several immunological abnormalities and that sIL-2R is able to bind IL-2. It is conceivable then that in these conditions the excess sIL-2R released in vivo by activated lymphoid cells or by neoplastic cells may somehow regulate IL-2-dependent processes. On the other hand, it cannot exclude that sIL-2R is a by-product without biological significance. Finally, it is puzzling that in many conditions in which an increase of blood sIL-2R values has been observed, MNCs display a decreased in vitro capacity to produce sIL-2R. These seemingly contrasting findings are discussed in the light of the data showing that sIL-2R production correlates with IL-2 production.

Antihypertriglyceridemia and anti-inflammatory activities of monascus-fermented dioscorea in streptozotocin-induced diabetic rats

The rice fermented by Monascus, called red mold rice (RMR), and has a long tradition in East Asia as a dietary staple. Monascus-fermented dioscorea called red mold dioscorea (RMD) contains various metabolites to perform the ability of reducing oxidative stress and anti-inflammatory response. We used Wistar rats and induced diabetes by injecting streptozotocin (STZ, 65 mg/kg i.p.). RMD was administered daily starting six weeks after disease onset. Throughout the experimental period, significantly (P < .05) lowered plasma glucose, triglyceride, cholesterol, free fatty acid and low density lipoprotein levels were observed in the RMD-treated groups. The RMD-treated diabetic rats showed higher activities of glutathione disulfide reductase, glutathione reductase, catalase and superoxide dismutase (P < .05) in the pancreas compared with the diabetic control rats. RMD also inhibited diabetes-induced elevation in the levels of interleukin (IL)-1β, IL-6, interferon-γ and tumor necrosis factor-α. Pancreatic β-cells damaged by STZ in the RMD supplemented groups were ameliorated. The results of this study clearly demonstrated that RMD possesses several treatment-oriented properties, including the control of hyperglycemia, antioxidant effects, pancreatic β-cell protection and anti-inflammatory effects. Considering these observations, it appears that RMD may be a useful supplement to delay the development of diabetes and its complications.

Type 1 Diabetes: Etiology, Immunology, and Therapeutic Strategies

Type 1 diabetes (T1D) is a chronic autoimmune disease in which destruction or damaging of the beta-cells in the islets of Langerhans results in insulin deficiency and hyperglycemia. We only know for sure that autoimmunity is the predominant effector mechanism of T1D, but may not be its primary cause. T1D precipitates in genetically susceptible individuals, very likely as a result of an environmental trigger. Current genetic data point towards the following genes as susceptibility genes: HLA, insulin, PTPN22, IL2Ra, and CTLA4. Epidemiological and other studies suggest a triggering role for enteroviruses, while other microorganisms might provide protection. Efficacious prevention of T1D will require detection of the earliest events in the process. So far, autoantibodies are most widely used as serum biomarker, but T-cell readouts and metabolome studies might strengthen and bring forward diagnosis. Current preventive clinical trials mostly focus on environmental triggers. Therapeutic trials test the efficacy of antigen-specific and antigen-nonspecific immune interventions, but also include restoration of the affected beta-cell mass by islet transplantation, neogenesis and regeneration, and combinations thereof. In this comprehensive review, we explain the genetic, environmental, and immunological data underlying the prevention and intervention strategies to constrain T1D.

Apoptosis of CD4+ CD25(high) T cells in type 1 diabetes may be partially mediated by IL-2 deprivation

Background

Type 1 diabetes (T1D) is a T-cell mediated autoimmune disease targeting the insulin-producing pancreatic β cells. Naturally occurring FOXP3⁺CD4⁺CD25^high regulatory T cells (T_regs) play an important role in dominant tolerance, suppressing autoreactive CD4⁺ effector T cell activity. Previously, in both recent-onset T1D patients and β cell antibody-positive at-risk individuals, we observed increased apoptosis and decreased function of polyclonal T_regs in the periphery. Our objective here was to elucidate the genes and signaling pathways triggering apoptosis in T_regs from T1D subjects.

Principal Findings

Gene expression profiles of unstimulated T_regs from recent-onset T1D (n = 12) and healthy control subjects (n = 15) were generated. Statistical analysis was performed using a Bayesian approach that is highly efficient in determining differentially expressed genes with low number of replicate samples in each of the two phenotypic groups. Microarray analysis showed that several cytokine/chemokine receptor genes, HLA genes, GIMAP family genes and cell adhesion genes were downregulated in T_regs from T1D subjects, relative to control subjects. Several downstream target genes of the AKT and p53 pathways were also upregulated in T1D subjects, relative to controls. Further, expression signatures and increased apoptosis in T_regs from T1D subjects partially mirrored the response of healthy T_regs under conditions of IL-2 deprivation. CD4⁺ effector T-cells from T1D subjects showed a marked reduction in IL-2 secretion. This could indicate that prior to and during the onset of disease, T_regs in T1D may be caught up in a relatively deficient cytokine milieu.

Conclusions

In summary, expression signatures in T_regs from T1D subjects reflect a cellular response that leads to increased sensitivity to apoptosis, partially due to cytokine deprivation. Further characterization of these signaling cascades should enable the detection of genes that can be targeted for restoring T_reg function in subjects predisposed to T1D.

N-3 polyunsaturated fatty acids modulate in-vitro T cell function in type I diabetic patients

In this work, we assessed the in-vitro effects of eicosapentaenoic acid (EPA; C20:5n-3) and docosahexaenoic acid (DHA; C22:6n-3) (final concentration, 15 microM) on T cell blastogenesis, interleukin-2 and -4 (IL-2, IL-4) secretion, fatty acid composition and intracellular oxidative status in type I diabetic patients with or without complications. Con A stimulated lymphocyte proliferation, glucose uptake, intracellular reduced glutathione levels and catalase activity were lower in diabetics as compared to controls, regardless to the presence of complications. EPA and DHA diminished T-lymphocyte proliferation and IL-2 production but enhanced IL-4 secretion in both diabetic and control groups. No changes in the levels of reduced glutathione and in the activities of catalase and SOD were observed in control T cells cultured in the presence of EPA and DHA. However, in diabetic patients, addition of n-3 PUFA to culture induced an increase in T cell levels of reduced glutathione and hydroperoxide, and in activities of catalase and SOD. Low levels of arachidonic acid (C20:4n-6) were found in plasma membrane phospholipids of lymphocytes from diabetic patients compared to controls. Incubation of lymphocytes with EPA and DHA was associated with an incorporation of these fatty acids in membrane phospholipids. In conclusion, the beneficial effects of n-3 PUFA on T cell functions in type I diabetes could be attributed to their suppressive action and modulation of cytokine secretion, and to the improvement of intracellular oxidative status.

Effect of diabetes mellitus on mycophenolate sodium pharmacokinetics and inosine monophosphate dehydrogenase activity in stable kidney transplant recipients

Effect of diabetes mellitus on mycophenolic acid (MPA) pharmacokinetics and catalytic activity of inosine monophosphate dehydrogenase (IMPDH) was investigated in maintenance kidney transplant recipients. Demographically matched diabetic (n=9) and nondiabetic (n=9) patients were included in a 12-hour open-label, steady-state study after oral administration of enteric-coated mycophenolate sodium. Concentrations of total MPA and free MPA, MPA-glucuronide, and acyl-MPA-glucuronide were measured and oral acetaminophen absorption was used as a marker for gastric-emptying rate. Median (range) of MPA area under the curve(0-12) was 36.7 (range, 16.4-116.4) mg*h/L in diabetic and 48.2 (range, 34.9-80.1) mg*h/L in nondiabetic patients (P=0.49). All other primary pharmacokinetic parameters, including time to maximum concentration, for total or unbound MPA as well as MPA metabolites were comparable. In contrast, IMPDH activity was 17.5+/-2.8 versus 46.6+/-2.5 nmol XMP/h/microg protein in diabetics and nondiabetics, respectively (P<0.0001) and was significantly lower in the diabetics irrespective of concomitant therapy with cyclosporine or tacrolimus. This study demonstrated that diabetes does not alter MPA pharmacokinetics when administered as enteric-coated mycophenolate sodium; however, IMPDH activity appeared to be significantly lower in patients with diabetes independent of the unbound or total concentrations of MPA. Further investigations are warranted to investigate the regulation of IMPDH enzyme in patients with diabetes.

Large-scale genetic fine mapping and genotype-phenotype associations implicate polymorphism in the IL2RA region in type 1 diabetes

Genome-wide association studies are now identifying disease-associated chromosome regions. However, even after convincing replication, the localization of the causal variant(s) requires comprehensive resequencing, extensive genotyping and statistical analyses in large sample sets leading to targeted functional studies. Here, we have localized the type 1 diabetes (T1D) association in the interleukin 2 receptor alpha (IL2RA) gene region to two independent groups of SNPs, spanning overlapping regions of 14 and 40 kb, encompassing IL2RA intron 1 and the 5' regions of IL2RA and RBM17 (odds ratio = 2.04, 95% confidence interval = 1.70-2.45; P = 1.92 x 10(-28); control frequency = 0.635). Furthermore, we have associated IL2RA T1D susceptibility genotypes with lower circulating levels of the biomarker, soluble IL-2RA (P = 6.28 x 10(-28)), suggesting that an inherited lower immune responsiveness predisposes to T1D.

Diabetes-induced decrease of adenosine kinase expression impairs the proliferation potential of diabetic rat T lymphocytes

The proliferative response of T lymphocytes is a crucial step in cell-mediated immunity. This study was undertaken to investigate the mechanisms leading to the impaired proliferative response of diabetic T lymphocytes. T cells that had been isolated from the spleen of normal rats and cultured in medium containing 20 mm glucose and no insulin displayed the same degree of proliferative impairment as cells isolated from diabetic rats. The rate of T-cell proliferation, when induced with concanavalin A or anti-CD3 and anti-CD28 antibodies, was not affected by the inhibition of nucleoside transporters. T cells cultured at high glucose concentrations in the absence of insulin displayed decreased expression of adenosine kinase, and released measurable extracellular quantities of adenosine. Under resting conditions, the level of cAMP was 5.9-fold higher in these cells compared to cells grown in low glucose and in the presence of insulin. Experiments with specific adenosine receptor agonists and antagonists showed that adenosine-induced suppression of diabetic T cell proliferation was mediated by the A2A adenosine receptor, but not by the A2B receptor. Treatment of diabetic T cells with 10 microm H-89, a specific protein kinase A inhibitor, restored T-cell proliferation. These results show that suppressed proliferation of diabetic T lymphocytes is evoked by the decreased expression of adenosine kinase, leading to the outflow of adenosine from the cell. Extracellular adenosine then stimulates the A2A receptor and induces cAMP production, leading to the activation of protein kinase A, and suppression of T-cell proliferation.

Multiple immuno-regulatory defects in type-1 diabetes

Susceptibility to immune-mediated diabetes (IMD) in humans and NOD mice involves their inherently defective T cell immunoregulatory abilities. We have followed natural killer (NK) T cell numbers in patients with IMD, both by flow cytometry using mAbs to the characteristic junctions found in the T cell receptors of this cell subtype, and by semiquantitative RT-PCR for the corresponding transcripts. Both before and after clinical onset, the representation of these cells in patients' PBMCs is reduced. We also report low numbers of resting CD4(+) CD25(+) T cells in IMD patients, a subset of T cells shown to have important immunoregulatory functions in abrogating autoimmunities in 3-day thymectomized experimental mice. Whereas a biased Th1 to Th2 cytokine profile has been suggested to underlie the pathogenesis of IMD in both species, we found defective production of IFN-gamma in our patients after in vitro stimulation of their PBMCs by phorbol-myristate acetate and ionomycin and both IFN-gamma and IL-4 deficiencies in V(alpha)24(+) NK T-enriched cells. These data suggest that multiple immunoregulatory T (Treg) cell defects underlie islet cell autoimmunity leading to IMD in humans and that these lesions may be part of a broad T cell defect.

Multiple immuno-regulatory defects in type-1 diabetes

Susceptibility to immune-mediated diabetes (IMD) in humans and NOD mice involves their inherently defective T cell immunoregulatory abilities. We have followed natural killer (NK) T cell numbers in patients with IMD, both by flow cytometry using mAbs to the characteristic junctions found in the T cell receptors of this cell subtype, and by semiquantitative RT-PCR for the corresponding transcripts. Both before and after clinical onset, the representation of these cells in patients' PBMCs is reduced. We also report low numbers of resting CD4(+) CD25(+) T cells in IMD patients, a subset of T cells shown to have important immunoregulatory functions in abrogating autoimmunities in 3-day thymectomized experimental mice. Whereas a biased Th1 to Th2 cytokine profile has been suggested to underlie the pathogenesis of IMD in both species, we found defective production of IFN-gamma in our patients after in vitro stimulation of their PBMCs by phorbol-myristate acetate and ionomycin and both IFN-gamma and IL-4 deficiencies in V(alpha)24(+) NK T-enriched cells. These data suggest that multiple immunoregulatory T (Treg) cell defects underlie islet cell autoimmunity leading to IMD in humans and that these lesions may be part of a broad T cell defect.

Specific deficiency of p56lck expression in T lymphocytes from type 1 diabetic patients

Peripheral T lymphocyte activation in response to TCR/CD3 stimulation is reduced in type 1 diabetic patients. To explore the basis of this deficiency, a comprehensive analysis of the signal transduction pathway downstream of the TCR/CD3 complex was performed for a cohort of patients (n = 38). The main result of the study shows that T cell hyporesponsiveness is positively correlated with a reduced amount of p56(lck) in resting T lymphocytes. Upon CD3-mediated activation, this defect leads to a hypophosphorylation of the CD3zeta-chain and few other polypeptides without affecting the recruitment of ZAP70. Other downstream effectors of the TCR/CD3 transduction machinery, such as phosphatidylinositol 3-kinase p85alpha, p59(fyn), linker for activation of T cells (LAT), and phospholipase C-gamma1, are not affected. In some patients, the severity of this phenotypic deficit could be linked to low levels of p56(lck) mRNA and resulted in the failure to efficiently induce the expression of the CD69 early activation marker. We propose that a primary deficiency in human type 1 diabetes is a defect in TCR/CD3-mediated T cell activation due to the abnormal expression of the p56(lck) tyrosine kinase.

Constitutive impaired TCR/CD3-mediated activation of T cells in IDDM patients co-exist with normal co-stimulation pathways

IDDM is a T cell-mediated autoimmune disease which is paradoxically associated with T cell functional deficiencies. The proliferative response of PBMC under CD3-, Vbeta2-, Vbeta8- and Vbeta7-stimulation was investigated in IDDM and NIDDM patients, non-diabetic first-degree relatives and control subjects. Despite normal surface expression of the TCR/CD3 complex, the TCR/CD3-mediated proliferation of PBMC from IDDM patients was significantly impaired compared to control subjects (P<0.05). This defect was specific for the autoimmune disease, constitutive and not linked to the class II MHC genotype, to metabolic disturbances or to presence of specific autoantibodies. Inefficient activation of T cells was not related to a lower capacity of CD28 to transduce co-stimulative signals because proliferative responses under CD2/CD28 stimulations were similar in IDDM and control groups. The IL-2/IL-2 receptor system was functional because unstimulated PBMC proliferated in response to increasing amounts of IL-2. Nevertheless, despite normal expression of CD25, addition of IL-2 did not normalize the proliferative defect linked to IDDM. In conclusion, excluding a faulty co-stimulation pathway, these results are in favour of a constitutive defect in the CD3/TCR transduction machinery, increasing sensitivity to apoptosis or anergy in T cells from IDDM patients.

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

Thymic T cell function in streptozotocin-treated (STZ) diabetic mice has been examined. STZ administration suppresses thymic T cell proliferation in response to mitogen stimulation in vitro. Secretion of IL-4 was dramatically reduced; however, secretion of IL-2 or IFN-gamma was not significantly inhibited. RT-PCR analysis of thymocyte RNA revealed that levels of IL-4 mRNA were dramatically decreased in STZ-treated mice. Levels of mRNA encoding IFN-gamma were similar, but the appearance was delayed in thymocytes derived from STZ-treated mice, implying differential regulation of IL-4 and IFN-gamma. Defective thymocyte proliferation was partially restored by exposure to IL-2 in vitro; however, IL-4 completely reversed the STZ-induced defect. Administration in vivo of IL-4 before STZ treatment reversed the STZ-induced thymocyte proliferation defect and prevented both pancreatic islet destruction and hyperglycemia. Thymocyte cell surface differentiation markers were not appreciably different from control mice. Collectively these experiments suggest that STZ treatment of mice reduces expression of IL-4 which is associated with development of autoimmune diabetes.

In vitro T cell activation in elderly individuals: failure in CD69 and CD71 expression

A large number of T cell dysfunctions have been observed in the elderly. The most widely observed is the inability of these cells to proliferate at a level comparable to T cells from young individuals after stimulation by mitogens. To better characterize T cell impairment, we have focused on the in vitro T cell activation, analyzing by flow cytometry the activation molecules CD69 and CD71 on mitogen-stimulated lymphocytes from young and elderly subjects. The results show that the percentages of CD69+ and CD71 + T cells were significantly decreased in cultures from elderly subjects when compared to values obtained culturing cells from young individuals. The differences observed seem not due to differences in CD4 and CD8 rates in the "old' cells that underwent activation, since, following activation, the pattern of CD4 and CD8 phenotypes was the same in both groups of subjects. Signals from CD69 are relevant in controlling cytokine gene expression because its stimulation leads to interleukin-2 production and increases its receptor expression. The interaction of this cytokine with its cellular receptor is an essential requirement for T lymphocytes to express CD71 and to start proliferation. Thus, a key role in the age-associated impairment of T cell activation could be played by an ineffective modulation of CD69 expression suggesting a defect in the signal transduction pathway of the T cell receptor-CD3 complex in elderly.

Cytokine production pathway in the elderly

It is well known that aging is associated with various alterations in lymphoid cell functions, particularly with a progressive decline in immune responsiveness to exogenous antigens and increasing incidence of autoimmune phenomena. Many studies have been focused on the mechanisms of the immunologic features of aging. this review describes our results of studies performed to determine the influence of age on the capacity to produce interleukin-2 (IL-2), interferon-gamma (IFN-gamma), interleukin-4 (IL-4), interleukin-t (IL-5), interleukin-6 (IL-6) and tumor necrosis factor (TNF). Mitogen-stimulated cultures of mononuclear cells (MNC) from human beings were assessed for cytokine-producing capacity. A significant decrease in IFN-gamma and IL-2 production by MNC cultures from elderly individuals was observed. No significant difference was instead observed between cultures from elderly individuals and those from young ones as regards TNF-alpha, IL-4 and IL-6 production. Mitogen or antigen-stimulated cultures of MNC from aged mice also displayed a significant decrease in IFN-gamma and IL-2 production as well as TNF-beta. Instead IL-4 and IL-5 production significantly increased in these cultures. We suggest that this imbalanced cytokine production may well account for the pattern of immune response which may be observed in the elderly, i.e. a normal or increased humoral response (including autoimmune responses) in face of a low T cell immune responsiveness.

Low bcl-2 expression and increased spontaneous apoptosis in T-lymphocytes from newly-diagnosed IDDM patients

The bcl-2 gene product has been shown to regulate apoptotic cell death, and its dysregulation has been shown to induce several abnormalities in the immune system. No data exist regarding bcl-2 expression in autoimmune diseases, such as human insulin-dependent diabetes mellitus (IDDM). We investigated bcl-2 protein expression by testing T lymphocytes from 15 newly-diagnosed (< 3 weeks) IDDM patients in comparison to 10 age-matched control subjects. The expression of bcl-2 on CD3+ lymphocyte subsets was investigated after membrane permeabilization by two- or three-colour immunofluorescence. When the percentage and mean fluorescence intensity (MFI) of bcl-2+/CD3+ cells from normal individuals and patients were compared, we found that bcl-2 expression within the CD3+ and CD4+ CD45R0+ T-cell populations was reduced significantly in IDDM patients (46.8 +/- 15.4 vs 79.6 +/- 11.7; 25.7 +/- 3.8 vs 47.15 +/- 5.7, respectively; p < 0.001). To establish whether low bcl-2 expression in T cells from newly-diagnosed patients reflects their susceptibility to death by an apoptotic process, we also evaluated DNA staining with propidium iodide in CD3+ lymphocyte suspension after a (24-72 h) culture period (spontaneous apoptosis). We found that IDDM patients have higher levels of spontaneous apoptosis (mean +/- SEM: 24 h = 4.6 +/- 0.8; 48 h = 9.9 +/- 1; 72 h = 12.8 +/- 1.1) than control subjects (24 h = 1.8 +/- 0.4; 48 h = 4.6 +/- 0.4; 72 h = 5.7 +/- 0.3; p < 0.02-0.001). Our study suggests that recent onset IDDM is characterised by reduced bcl-2 expression, which in turn may be associated with the increased spontaneous apoptosis we observed.

Soluble interleukin-2 receptor levels in patients with dilated cardiomyopathy. Correlation with disease severity and cardiac autoantibodies

BACKGROUND

There is evidence that autoimmunity plays an important role in the initiation and progression of myocardial injury in dilated cardiomyopathy. Abnormalities of both cellular and humoral immunity have been described in this disease. Soluble interleukin-2 receptor (sIL-2R) levels in the serum reflect activation of T lymphocytes in the periphery or in tissues. The present study explored the possibility that activation of cellular immunity is frequent in patients with idiopathic dilated cardiomyopathy and may have functional consequences.

METHODS AND RESULTS

Serum sIL-2R levels were determined with an enzyme-linked immunosorbent assay in 50 dilated cardiomyopathy patients, 30 patients with ischemic heart disease, and 22 normal control subjects. In addition, the presence of anti-beta-receptor and antimyosin antibodies was sought in the serum of cardiomyopathy patients. High sIL-2R levels (> 1400 pg/mL) were found in 38% of the dilated cardiomyopathy patients but only 6% of the ischemic heart disease patients. The group of sIL-2R-positive patients was characterized by higher average age, a higher percentage of women, and more severe disease (lower ejection fraction, higher left ventricular filling pressures, and lower cardiac output). Although the prevalence of cardiac autoantibodies did not correlate with the presence of high sIL-2R levels, higher titers of autoantibodies were found predominantly in the sIL-2R-positive group.

CONCLUSIONS

T-lymphocyte activation, as reflected in elevated sIL-2R levels, is frequent in patients with dilated cardiomyopathy and is associated with more severe disease. Cellular and humoral immune activation may correlate with progression of the disease process.

Defective T cell receptor/CD3 complex signaling in human type I diabetes

The autoimmune process leading to the destruction of pancreatic beta-cells is mediated by T lymphocytes. Peripheral T cells from subjects with preclinical and clinical type I diabetes respond weakly in vitro to lectin stimulation. We, therefore, investigated in a group of newly diagnosed diabetic patients the presence of a defect in the signal transduction pathway of the T cell receptor (TcR)/CD3 complex. Following stimulation with anti-CD3-coupled beads, the proliferative response in diabetic T cells was significantly decreased in comparison with that from normal T cells. Interestingly, addition of either recombinant interleukin (IL)-2 or phorbol 12-myristate 13-acetate to the cell culture was able to completely restore impaired anti-CD3-induced proliferation in diabetic T cells, suggesting the presence of a defect through the TcR/CD3 pathway, located upstream of protein kinase C (PKC) activation and resulting in low IL-2 production and proliferation. Intracellular Ca2+ measurements by Fluo-3 labeling and flow cytometry analysis on diabetic and control T cells after anti-CD3 stimulation gave comparable results, indicating that this defect does not involve events leading to intracellular Ca2+ mobilization. In contrast, anti-CD3 stimulation of diabetic T cells resulted in a marked impairment of PKC translocation and CD69 antigen expression, as assessed by peptide substrate phosphorylation and by flow cytometry analysis, respectively. Taken together, our data clearly show the presence in individuals at the onset of the disease of an in vitro defect in the signal transduction pathway of the TcR/CD3 complex, resulting in ineffective PKC activation which is not able to induce normal IL-2 production and proliferation of diabetic T cells.

In vitro cytokine production by HLA-B8,DR3 positive subjects

It is well known that healthy subjects carrying the HLA-B8,DR3 haplotype may show an impairment of immune system, the T cells being the most affected. To gain insight into the mechanism(s) of the impairment displayed by these subjects, efforts have been centered on the study of in vitro cytokine production because of the pivotal role played by these mediators in the activation and control of several immune functions. The available results indicate that the ability to several immune functions. The available results indicate that the ability to produce interleukin-1 (IL-1), IL-2 and the soluble form of its receptor (sIL-2R) is impaired in HLA-B8,DR3 positive healthy subjects. To better characterize the cytokine production capacity of HLA-B8,DR3 positive subjects, we have investigated the pattern of in vitro production of IL-2, sIL-2R, IL-4. IL-6 and gamma-interferon (gamma-IFN) by mononuclear cells from HLA-B8, DR3 positive subjects after phytohaemoagglutinin stimulation. A significant decrease of IL-2, sIL-2R and gamma-IFN production by HLA-B8,DR3 positive subjects was observed. No significant difference was instead found between the HLA-B8,DR3 positive subjects and the negative ones as regards IL-4 and IL-6 production. We suggest that this imbalanced cytokine production may well account for the pattern of immune response that may observed in HLA-B8,DR3 positive subjects, i.e. a normal or increased humoral response in face of a low T cell immune responsiveness.

Study of T-cell activation in type I diabetic patients and pre-type I diabetic subjects by cytometric analysis: antigen expression defect in vitro

In Type I diabetes the observation of a decreased release of interleukin-2 (IL-2) and soluble IL-2 receptors by means of stimulated lymphocytes in vitro indicates that a primary immunoregulatory defect may be involved. To confirm this hypothesis we investigated the T-cell activation trend, evaluating the surface expression of IL-2 receptor (CD25), transferrin (CD71), HLA class II (DR), and CD69 phenotypes after in vitro stimulation with phytohemagglutinin (PHA; 1 and 10 micrograms/ml) and concanavalin A (12.5 micrograms/ml) in six newly diagnosed Type I diabetics and six islet cell- and insulin autoantibody-positive first-degree relatives. As controls were studied six long-standing Type I diabetics and six healthy subjects. T-cell cultures from the four groups were performed on the same day and examined at 0, 24, 48, 96, 120, and 144 hr. Cytometric analysis was performed, keeping PBMC gating constant on the basis of physical parameters (scatter and volume). Using both PHA concentrations, a lower level of CD25, CD71, CD69, and DR antigen expression was found in newly diagnosed patients at all observation times with respect to control cultures (P < 0.001). Unexpectedly, pre-Type I diabetic subjects, after 1 microgram/ml of PHA, showed a significantly reduced expression of CD69 (P < 0.001) and CD71 (P < 0.001). The levels remained low, also with high PHA, at the different observation periods, while CD25 expression was found to be reduced in prediabetics only after 1 micrograms/ml of PHA (P < 0.001). The long-standing patients showed a T cell activation trend very close to the latter. Our data show that in Type I diabetes and in the early phases of the disease, the initial activation signal(s) appears to be affected, particularly with one or more subsequent events necessary to initiate the appearance of "activation antigens." This study suggests that the natural history of immunoregulation in pre-Type I and Type I diabetes is characterized by a primary defect in this system, which also persists in patients with long-standing disease.

Soluble interleukin-2 receptor release defect in vitro in elderly subjects

The evidence from several studies indicates that as individuals age, they may display immune dysfunctions, mostly T cell dysfunctions. Recently, a soluble form of the receptor for interleukin-2 (IL-2) (sIL-2R) has been demonstrated in human sera and in vitro stimulated culture supernatants from human T lymphocytes. In the present paper, we report in vitro sIL-2R production from peripheral blood mononuclear cells in elderly subjects. The results show that no difference exists for unstimulated cultures, whereas after mitogen stimulation the elderly subjects showed the lowest values compared with young ones. These findings suggest that sIL-2R may provide a new tool for the study of T lymphocyte dysfunctions in old age.

The soluble receptor of interleukin 2 is not a serum marker of the autoimmune activity in type I diabetes mellitus

In order to determine if soluble interleukin 2 receptor (IL2R) was useful as a marker in screening for early Type 1 diabetes and in monitoring immunological treatment, we assayed serum IL2R levels in 67 controls, 43 patients with newly diagnosed diabetes and 28 first degree relatives of diabetic patients (5 subjects were islet cell antibody positive). In 23 diabetes, specimens were analysed at 3 and 6 months after diagnosis whether or not cyclosporin A was administered. Seven patients were in a clinical trial using anti IL2R monoclonal antibody and cyclosporin A. Since IL2R level in the normal population is elevated in the first 5 years of life then decreases until adulthood (age:IL2R correlation between 0 and 15 years: r = -0.42, P less than 0.05), subjects were carefully matched in age. In recent onset diabetes, this negative correlation disappeared and IL2R levels tended to decrease particularly in younger subjects. In Type 1 prediabetic subjects presenting persistent islet-cell antibody serum IL2R was not elevated. During immunological treatment of recent onset diabetes, serum IL2R remained stable and was not modified by cyclosporin A. As expected IL2R became undetectable during treatment with anti IL2R MC Ab. But it rebounded when treatment was stopped with no effect on remission. We concluded that IL2R levels in Type 1 diabetic patients is not useful in screening autoimmune activity or in evaluating the effectiveness of immunosuppressors.

Anti-interleukin 2 receptor antibody attenuates low-dose streptozotocin-induced diabetes in mice

Recent evidence indicates that activated T cells and macrophages play an important role in the induction of insulitis and diabetes in certain strains of mice treated with multiple subdiabetogenic doses of streptozotocin. In the present study, we treated C57BL/6J mice with five daily doses of 40 mg/ml streptozotocin and examined the prophylactic effect of an anti-interleukin 2 receptor monoclonal antibody (PC61). In mice treated with streptozotocin, interleukin 2 receptor-positive mononuclear cells were shown to infiltrate into the islets and soluble interleukin 2 receptors in the sera were significantly increased compared with control mice. The administration of PC61 to the mice attenuated the insulitis, and diminished interleukin 2 receptor-positive cells from islets and soluble interleukin 2 receptors in the sera. Moreover, the administration of PC61 significantly reduced the development of hyperglycaemia shown in these mice (12.8 +/- 1.1 mmol/l vs 18.5 +/- 0.7 mmol/l, p less than 0.005). As judged by flow cytometric analysis, this antibody did not cause any changes in either spleen cell counts or T cell subsets. Interleukin 2 receptors were expressed on a minor population of spleen cells regardless of treatment with PC61 (STZ + normal rat IgG: 2.1 +/- 0.3%, STZ + PC61: 2.4 +/- 0.3%). Even after stimulation of spleen cells with concanavalin A or alloantigen, interleukin 2 receptor expression was not significantly different between the two groups. Our studies suggest that interleukin 2 receptor-positive activated T cells or macrophages are important in the development of multi-low-dose streptozotocin diabetes and that an anti-interleukin 2 receptor antibody can attenuate this process.

Soluble interleukin-2 receptor secretion defect in vitro in HLA-B8, DR3 positive subjects

Several studies have shown that HLA-B8,DR3 positive subjects may display T cell dysfunctions. Recently, a soluble form of the receptor for IL-2 (sIL-2R) has been demonstrated in human sera and in vitro-stimulated culture supernatant from human T lymphocytes. In the present paper we report sIL-2R serum levels and sIL-2R production from peripheral blood mononuclear cells in HLA-B8,DR3 positive subjects. We found that HLA-B8,DR3 positive subjects have the highest values of serum sIL-2R, but comparing the values of these subjects with those of negative ones no significant difference was observed. As regards the in vitro production of sIL-2R, no difference exists for unstimulated cultures, whereas after stimulation, the HLA-B8,DR3 positive subjects showed the lowest values compared with negative ones. It is noteworthy that these changes are observed in autoimmune diseases linked to this HLA phenotype.