Regulation of the IL-10 production by human T cells

The interplay of inflammation, exosomes and Ca2+ dynamics in diabetic cardiomyopathy

Diabetes mellitus is one of the prime risk factors for cardiovascular complications and is linked with high morbidity and mortality. Diabetic cardiomyopathy (DCM) often manifests as reduced cardiac contractility, myocardial fibrosis, diastolic dysfunction, and chronic heart failure. Inflammation, changes in calcium (Ca²⁺) handling and cardiomyocyte loss are often implicated in the development and progression of DCM. Although the existence of DCM was established nearly four decades ago, the exact mechanisms underlying this disease pathophysiology is constantly evolving. Furthermore, the complex pathophysiology of DCM is linked with exosomes, which has recently shown to facilitate intercellular (cell-to-cell) communication through biomolecules such as micro RNA (miRNA), proteins, enzymes, cell surface receptors, growth factors, cytokines, and lipids. Inflammatory response and Ca²⁺ signaling are interrelated and DCM  has been known to adversely affect many of these signaling molecules either qualitatively and/or quantitatively. In this literature review, we have demonstrated that Ca²⁺ regulators are tightly controlled at different molecular and cellular levels during various biological processes in the heart. Inflammatory mediators, miRNA and exosomes are shown to interact with these regulators, however how these mediators are linked to Ca²⁺ handling during DCM pathogenesis remains elusive. Thus, further investigations are needed to understand the mechanisms to restore cardiac Ca²⁺ homeostasis and function, and to serve as potential therapeutic targets in the treatment of DCM.

Human Cytomegalovirus pUL11, a CD45 Ligand, Disrupts CD4 T Cell Control of Viral Spread in Epithelial Cells

Human cytomegalovirus (HCMV) encodes numerous immunomodulatory genes that facilitate its persistence. Previously described mechanisms by which HCMV avoids T cell control typically involve evasion of detection by infected cells. Here, we show that the virus also inhibits T cells directly via an interaction between the pUL11 glycoprotein on infected cells and the CD45 phosphatase on T cells. The antiviral functions of CD4 T cells are impaired as a result of this interaction, largely via induced interleukin 10 (IL-10) secretion in the CD4 T cell central memory compartment, resulting in enhanced viral spread. This establishes CD45 as an inhibitory receptor that regulates antiviral T cell functions and has parallels with the manipulation of natural killer (NK) cells by HCMV. By coculturing donor T cells with HCMV-infected epithelial cells, we observed that CD4 T cells can respond to epithelial cell antigen presentation and can control HCMV spread via cytolytic and cytokine-dependent mechanisms. pUL11 impairs both mechanisms. We showed that pUL11-induced IL-10 secretion requires IL-2, mTOR, and T cell receptor signaling. This characterization of the effects of the pUL11-CD45 interaction may allow for the development of new antiviral therapies and treatments for inflammatory disorders. IMPORTANCE Human cytomegalovirus (HCMV) is adept at avoiding its host's immune defenses, both by evading detection and by directly inhibiting immune cells. This can lead to a loss of control of the infection, and dangerous disease can result, particularly in cases in which an individual's immune system is immature, weak, or suppressed. T cells form a crucial part of the response to HCMV and are used in cellular HCMV therapies. We show that an interaction between a viral glycoprotein (pUL11) and a T cell surface receptor (CD45) impairs T cell memory functions and allows for increased viral spread. This defines a new immunomodulatory strategy for the virus as well as a new T cell regulatory mechanism. These results are important, as they increase our understanding of how T cells function and how HCMV disrupts them. This will allow for the development of new antiviral therapies that restore T cell functions and indicates a new target for controlling pathological T cell disorders.

The Potential Advantage of Targeting Both PD-L1/PD-L2/PD-1 and IL-10-IL-10R Pathways in Acute Myeloid Leukemia

Tumor cells promote the suppression of host anti-tumor type 1 T cell responses by various mechanisms, including the upregulation of surface inhibitory molecules such as programmed death ligand (PD-L)-1, and the production of immunosuppressive cytokines such as interleukin-10 (IL-10). There are over 2000 trials investigating PD-L1 and/or its receptor programmed-death 1 (PD-1) blockade in cancer, leading to the approval of PD-1 or PD-L1 inhibitors in several types of solid cancers and in hematological malignancies. The available data suggest that the molecule PD-L1 on antigen-presenting cells suppresses type 1 T cell immune responses such as cytotoxicity, and that the cytokine IL-10, in addition to downregulating immune responses, increases the expression of inhibitory molecule PD-L1. We hypothesize that the manipulation of both the co-inhibitory network (with anti-PD-L1 blocking antibodies) and suppressor network (with anti-IL-10 blocking antibodies) is an attractive immunotherapeutic intervention for acute myeloid leukemia (AML) patients ineligible for standard treatment with chemotherapy and hematopoietic stem cell transplantation, and with less severe adverse reactions. The proposed combination of these two immunotherapies represents a new approach that can be readily translated into the clinic to improve the therapeutic efficacy of AML disease treatment.

OX40 costimulation by a chimeric antigen receptor abrogates CD28 and IL-2 induced IL-10 secretion by redirected CD4(+) T cells

Adoptive therapy with chimeric antigen receptor (CAR) redirected T cells recently showed remarkable anti-tumor efficacy in early phase clinical trials; self-repression of the immune response by T-cell secreted cytokines, however, is still an issue raising interest to abrogate the secretion of repressive cytokines while preserving the panel of CAR induced pro-inflammatory cytokines. We here revealed that T-cell activation by a CD28-ζ signaling CAR induced IL-10 secretion, which compromises T cell based immunity, along with the release of pro-inflammatory IFN-γ and IL-2. T cells stimulated by a ζ CAR without costimulation did not secrete IL-2 or IL-10; the latter, however, could be induced by supplementation with IL-2. Abrogation of CD28-ζ CAR induced IL-2 release by CD28 mutation did not reduce IL-10 secretion indicating that IL-10 can be induced by both a CD28 and an IL-2 mediated pathway. In contrast to the CD28-ζ CAR, a CAR with OX40 (CD134) costimulation did not induce IL-10. OX40 cosignaling by a 3rd generation CD28-ζ-OX40 CAR repressed CD28 induced IL-10 secretion but did not affect the secretion of pro-inflammatory cytokines, T-cell amplification or T-cell mediated cytolysis. IL-2 induced IL-10 was also repressed by OX40 co-signaling. OX40 moreover repressed IL-10 secretion by regulatory T cells which are strong IL-10 producers upon activation. Taken together OX40 cosignaling in CAR redirected T cell activation effectively represses IL-10 secretion which contributes to counteract self-repression and provides a rationale to explore OX40 co-signaling CARs in order to prolong a redirected T cell response.

ASGR1 and Its Enigmatic Relative, CLEC10A

The large family of C-type lectin (CLEC) receptors comprises carbohydrate-binding proteins that require Ca²⁺ to bind a ligand. The prototypic receptor is the asialoglycoprotein receptor-1 (ASGR1, CLEC4H1) that is expressed primarily by hepatocytes. The early work on ASGR1, which is highly specific for N-acetylgalactosamine (GalNAc), established the foundation for understanding the overall function of CLEC receptors. Cells of the immune system generally express more than one CLEC receptor that serve diverse functions such as pathogen-recognition, initiation of cellular signaling, cellular adhesion, glycoprotein turnover, inflammation and immune responses. The receptor CLEC10A (C-type lectin domain family 10 member A, CD301; also called the macrophage galactose-type lectin, MGL) contains a carbohydrate-recognition domain (CRD) that is homologous to the CRD of ASGR1, and thus, is also specific for GalNAc. CLEC10A is most highly expressed on immature DCs, monocyte-derived DCs, and alternatively activated macrophages (subtype M2a) as well as oocytes and progenitor cells at several stages of embryonic development. This receptor is involved in initiation of T_H1, T_H2, and T_H17 immune responses and induction of tolerance in naïve T cells. Ligand-mediated endocytosis of CLEC receptors initiates a Ca²⁺ signal that interestingly has different outcomes depending on ligand properties, concentration, and frequency of administration. This review summarizes studies that have been carried out on these receptors.

Stories From the Dendritic Cell Guardhouse

Phagocytic cells [dendritic cells (DCs), macrophages, monocytes, neutrophils, and mast cells] utilize C-type (Ca²⁺-dependent) lectin-like (CLEC) receptors to identify and internalize pathogens or danger signals. As monitors of environmental imbalances, CLEC receptors are particularly important in the function of DCs. Activation of the immune system requires, in sequence, presentation of antigen to the T cell receptor (TCR) by DCs, interaction of co-stimulatory factors such as CD40/80/86 on DCs with CD40L and CD28 on T cells, and production of IL-12 and/or IFN-α/β to amplify T cell differentiation and expansion. Without this sequence of events within an inflammatory environment, or in a different order, antigen-specific T cells become unresponsive, are deleted or become regulatory T cells. Thus, the mode by which CLEC receptors on DCs are engaged can either elicit activation of T cells to achieve an immune response or induce tolerance. This minireview illustrates these aspects with Dectin-1, DEC205, the mannose receptor and CLEC10A as examples.

CaMKII Activity in the Inflammatory Response of Cardiac Diseases

Inflammation is a physiological process by which the body responds to external insults and stress conditions, and it is characterized by the production of pro-inflammatory mediators such as cytokines. The acute inflammatory response is solved by removing the threat. Conversely, a chronic inflammatory state is established due to a prolonged inflammatory response and may lead to tissue damage. Based on the evidence of a reciprocal regulation between inflammation process and calcium unbalance, here we described the involvement of a calcium sensor in cardiac diseases with inflammatory drift. Indeed, the Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) is activated in several diseases with an inflammatory component, such as myocardial infarction, ischemia/reperfusion injury, pressure overload/hypertrophy, and arrhythmic syndromes, in which it actively regulates pro-inflammatory signaling, among which includes nuclear factor kappa-B (NF-κB), thus contributing to pathological cardiac remodeling. Thus, CaMKII may represent a key target to modulate the severity of the inflammatory-driven degeneration.

An agent-based model of leukocyte transendothelial migration during atherogenesis

A vast amount of work has been dedicated to the effects of hemodynamics and cytokines on leukocyte adhesion and trans-endothelial migration (TEM) and subsequent accumulation of leukocyte-derived foam cells in the artery wall. However, a comprehensive mechanobiological model to capture these spatiotemporal events and predict the growth and remodeling of an atherosclerotic artery is still lacking. Here, we present a multiscale model of leukocyte TEM and plaque evolution in the left anterior descending (LAD) coronary artery. The approach integrates cellular behaviors via agent-based modeling (ABM) and hemodynamic effects via computational fluid dynamics (CFD). In this computational framework, the ABM implements the diffusion kinetics of key biological proteins, namely Low Density Lipoprotein (LDL), Tissue Necrosis Factor alpha (TNF-α), Interlukin-10 (IL-10) and Interlukin-1 beta (IL-1β), to predict chemotactic driven leukocyte migration into and within the artery wall. The ABM also considers wall shear stress (WSS) dependent leukocyte TEM and compensatory arterial remodeling obeying Glagov's phenomenon. Interestingly, using fully developed steady blood flow does not result in a representative number of leukocyte TEM as compared to pulsatile flow, whereas passing WSS at peak systole of the pulsatile flow waveform does. Moreover, using the model, we have found leukocyte TEM increases monotonically with decreases in luminal volume. At critical plaque shapes the WSS changes rapidly resulting in sudden increases in leukocyte TEM suggesting lumen volumes that will give rise to rapid plaque growth rates if left untreated. Overall this multi-scale and multi-physics approach appropriately captures and integrates the spatiotemporal events occurring at the cellular level in order to predict leukocyte transmigration and plaque evolution.

Ca(2+) -related signaling events influence TLR9-induced IL-10 secretion in human B cells

Suppressory B-cell function controls immune responses and is mainly dependent on IL-10 secretion. Pharmacological manipulation of B-cell-specific IL-10 synthesis could, thus, be therapeutically useful in B-cell chronic lymphocytic leukemia, transplantation, autoimmunity and sepsis. TLR are thought to play a protagonistic role in the formation of IL-10-secreting B cells. The aim of the study was to identify the molecular events selectively driving IL-10 production in TLR9-stimulated human B cells. Our data highlight the selectivity of calcineurin inhibitors in blocking TLR9-induced B-cell-derived IL-10 transcription and secretion, while IL-6 transcription and release, B-cell proliferation, and differentiation remain unaffected. Nevertheless, TLR9-induced IL-10 production was found to be independent of calcineurin phosphatase activity and was even negatively regulated by NFAT. In contrast to TLR9-induced IL-6, IL-10 secretion was highly sensitive to targeting of spleen tyrosine kinase (syk) and Bruton's tyrosine kinase. Further analyses demonstrated increased phosphorylation of Ca(2+) /calmodulin kinase II (CaMKII) in TLR9-stimulated B cells and selective reduction of TLR9-induced secretion of IL-10 upon treatment with CaMKII inhibitors, with negligible impact on IL-6 levels. Altogether, our results identify calcineurin antagonists as selective inhibitors of IL-10 transcription and syk/Bruton´s tyrosine kinase-induced Ca(2+) /calmodulin- and CaMKII-dependent signaling as a pathway regulating the release of TLR9-induced B-cell-derived IL-10.

Effect of activated human polymorphonuclear leucocytes on T lymphocyte proliferation and viability

Human polymorphonuclear leucocytes (PMN) are thought to be immunosuppressive. The suppressive mechanism(s) used by PMN are, however, not well defined and in this study they were analysed using T-cell responses to CD3(+) CD28 monoclonal antibodies (mAb) as a readout. We demonstrate that in vitro activated PMN (PMN(act)) can, without any T-cell interaction, induce apparent T-cell suppression by inhibiting the stimulatory capacity of the CD3 mAb. However, a cell-directed suppression of T-cell proliferation was observed when PMN(act) were added to pre-activated T cells that are already committed to polyclonal proliferation. This suppression was partially reversed by catalase addition (P < 0·01) and largely reversed by addition of exogenous interleukin-2 (P < 0·001) but was not significantly reduced by nitric oxide synthase inhibition, myeloperoxidase inhibition or addition of excess arginine. Following removal of PMN(act) , suppressed T cells could respond normally to further stimulation. In addition to suppressing proliferation, co-culture with PMN(act) also induced a significant decrease in T-cell viability that was reversed by catalase addition (P < 0·05). The addition of the arginase inhibitor N-hydroxy-nor-l-arginine induced both a further significant, catalase-sensitive, loss in T-cell viability and increased nitrite release (P < 0·001). These data demonstrate that PMN, when activated, can both induce T-cell death and reversibly inhibit proliferation of activated T cells. The mechanisms underlying these distinct processes and the effects of arginase inhibitors on PMN induced cytotoxicity merit further investigation.

Calcium/calmodulin-dependent protein kinase II regulates IL-10 production by human T lymphocytes: a distinct target in the calcium dependent pathway

Calcium (Ca2+) plays an essential role in lymphocyte activation and differentiation by affecting signaling pathways leading to cytokine production. Among the enzymes responding to calcium increase, Ca2+/calmodulin-dependent protein kinase II (CaMKII) has been involved in anergy with a still poorly characterized role. IL-10 produced by different T lymphocyte subpopulations is critical mediator of tolerance. We tested the hypothesis that CaMKII may be involved in IL-10 production. We report that CaMKII upregulates IL-10 production by primary human T lymphocytes stimulated through the antigen receptor or bypassing that. Overexpression of constitutively active mutant forms of Calcineurin or CaMKII specifically increase IL-10 protein product and IL-10 mRNA accumulation in T lymphocytes. By cotransfecting constitutively active CaMKII with luciferase reporter plasmids carrying specific fragments or the whole IL-10 promoter, we show that CaMKII specifically activates IL-10 promoter activity, whereas it inhibits IL-2 and IL-4 promoter. This effect is mediated by the first 500 bp fragment, which contains binding sites for Myocyte Enhancer Factor-2 (MEF2). A constitutively active mutant of CaMKII activated a luciferase reporter plasmid under the control of MEF2, when cotransfected in T lymphocytes stimulated by Ionomycin and PMA, whereas its inhibitor KN-62 inhibited MEF2 binding in cell lysates of the same cells. Moreover, overexpression of MEF2 enhanced by 2.5-fold IL-10 promoter activity. Our data for the first time suggest a distinct role of CaMKII in the induction of anergy in T lymphocytes, by differential regulation of IL-10 and IL-2 gene transcription suggest MEF2 as a molecular target which can integrate different calcium signals.

Renal transplant recipients have elevated frequencies of circulating myeloid-derived suppressor cells

BACKGROUND

Cancer, particularly cutaneous squamous cell carcinoma (SCC), is a major cause of mortality in renal transplant recipients (RTRs). Myeloid-derived suppressor cells (MDSC) play a central role in suppressing cancer immunosurveillance but their potential mobilisation in RTRs and levels relative to those of other immunoregulatory dendritic cell (DC) populations have not been analysed.

METHODS

The circulating frequencies of MDSC and DC were analysed by multicolour flow cytometry in immunocompetent patients without (n = 13) or with (ICI-SCC(Pos), n = 14) current SCC, normal donors (NDs, n = 34), chronic kidney disease patients (CKD patients, n = 22) and RTRs (n = 31).

RESULTS

Compared to NDs, RTRs had significantly elevated levels of both CD14(Neg) and CD14(Pos) MDSC subsets (P < 0.001), while CKD patients and ICI-SCC(Pos) had significantly elevated levels of only the CD14(Neg)-MDSC subset. DC frequencies were significantly decreased in RTRs and CKD patients but were at normal levels in ICI-SCC(Pos). The MDSC/DC ratio was significantly elevated (P < 0.05) in RTRs (median = 5.7), CKD patients (median = 3.2) and ICI-SCC(Pos) (median = 3.5) relative to NDs (median = 0.7). The use of immunosuppressive drugs in CKD patients and past/current occurrence of SCC in RTRs was associated with significantly increased CD14(Neg)-MDSC frequencies. MDSC enriched from RTRs, when co-cultured with activated NDs T cells significantly suppressed extracellular IL-10 levels and can, when activated with formyl-methionyl-leucyl-phenylalanine, inhibit T-cell proliferation.

CONCLUSIONS

RTRs, CKD patients and ICI-SCC(Pos) have increased MDSC frequencies and MDSC/DC ratios. These changes may impact on cancer immunosurveillance. Therefore, MDSC represent both a potential therapeutic target and prognostic marker in these patients, with respect to the development of SCC and other malignancies.

Exogenous soluble VEGF receptor-1 (sFlt-1) regulates Th1/Th2 cytokine production from normal placental explants via intracellular calcium

OBJECTIVE

The increase of soluble VEGF-Receptor 1 (sFlt-1) is thought to contribute to the pathogenesis of preeclampsia. Soluble VEGF-Receptor 1 binds to circulating free VEGF and PLGF and this cascade is associated with endothelial dysfunction, a prominent feature of preeclampsia. Preeclampsia is also associated with excessive maternal response to pro-inflammatory stimuli manifesting as an imbalance of Th1/Th2 cytokine production at the maternal-fetal interface. Whether increased sFlt-1 expression has any effect on placental production of Th1/Th2 cytokines IL-10 and TNF-alpha is yet to be investigated. The aim of this study is to examine if exogenous sFlt-1 can regulate Th1/Th2 cytokines IL-10 and TNF-alpha production from normal placental explants via intracellular calcium release.

METHODS

Placental explants were taken from the decidual surface of normal non-laboured term placentas (n = 11).Villous explants were cultured with increasing concentrations of sFlt-1. The dose effect of sFlt-1 on placental Th1 and Th2 cytokine production (TNF-alpha and IL-10) were examined. Free PLGF, VEGF and sFlt-1 concentrations in the conditioned medium were also measured. Intracellular calcium blocker, 1,2-bis-(o-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid, tetra(acetoxymethyl)-ester (BAPTA/AM) was applied to investigate whether the changes in cytokine concentration were mediated by intracellular free calcium.

RESULTS

Placental IL-10 and TNF-alpha production were significantly increased after sFlt-1 incubation. The increase in IL-10 can be inhibited by BAPTA/AM. Soluble Flt-1 and free PLGF concentration in the conditioned medium was not changed. Free VEGF concentration in the conditioned medium was not detectable.

CONCLUSION

Exogenous sFlt-1 can increase TNF-alpha and IL-10 production from normal placental explants. The change in Th1/Th2 cytokine level may be mediated by intracellular free calcium.

An ensemble of models of the acute inflammatory response to bacterial lipopolysaccharide in rats: results from parameter space reduction

In previous work, we developed an 8-state nonlinear dynamic model of the acute inflammatory response, including activated phagocytic cells, pro- and anti-inflammatory cytokines, and tissue damage, and calibrated it to data on cytokines from endotoxemic rats. In the interest of parsimony, the present work employed parametric sensitivity and local identifiability analysis to establish a core set of parameters predominantly responsible for variability in model solutions. Parameter optimization, facilitated by varying only those parameters belonging to this core set, was used to identify an ensemble of parameter vectors, each representing an acceptable local optimum in terms of fit to experimental data. Individual models within this ensemble, characterized by their different parameter values, showed similar cytokine but diverse tissue damage behavior. A cluster analysis of the ensemble of models showed the existence of a continuum of acceptable models, characterized by compensatory mechanisms and parameter changes. We calculated the direct correlations between the core set of model parameters and identified three mechanisms responsible for the conversion of the diverse damage time courses to similar cytokine behavior in these models. Given that tissue damage level could be an indicator of the likelihood of mortality, our findings suggest that similar cytokine dynamics could be associated with very different mortality outcomes, depending on the balance of certain inflammatory elements.

Interferon-gamma (IFN-gamma): a possible prognostic marker for clearance of high-risk human papillomavirus (HPV)

OBJECTIVES

The goal of this study was to identify cytokines that may predict high-risk HPV clearance or persistence in untreated patients with mild dysplasia or less of the uterine cervix.

METHODS

A prospective analysis was performed on 57 patients who harbored high-risk HPV with histologically verified mild dysplasia or less between May 2005 and March 2006. All patients underwent follow-up evaluation at 12 months. Real-time PCR was used to quantify interferon-gamma (IFN-gamma), interleukin-10 (IL-10), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha) transcripts. Hybrid Capture II testing was used to detect HPV DNA.

RESULTS

Among the 57 patients that were untreated with mild dysplasia, or less, 46 (80.7%) had no detectable HPV after 12 months of follow-up. Univariate analysis showed that a negative HPV test, of untreated mild dysplasia or less, occurred in 93.3% (28/30) of patients who were IFN-gamma-positive and in 66.7% (18/27) of patients who were IFN-gamma-negative (P=0.0109). Other factors such as age, lesion grade in the colposcopic biopsy, IL-10, IL-6, TNF-alpha, day of menstrual cycle, smoking, and use of oral contraceptives were not significantly associated with high-risk HPV negative or positive results after 12-months of follow-up in patients with untreated mild dysplasia or less. The multivariate logistic regression analysis showed that only IFN-gamma-positive results were significantly associated with clearance of high-risk HPV after 12 months of follow-up (OR: 8.26; 95% CI: 1.24-54.94).

CONCLUSIONS

These results suggest that intralesional IFN-gamma may be a prognostic marker for clearance of high-risk HPV.

Persistent IL-10 production is required for glioma growth suppressive activity by Th1-directed effector cells after stimulation with tumor lysate-loaded dendritic cells

Injection of dendritic cells (DC) pulsed with tumor antigens is a novel treatment strategy against malignancies, and aims to elicit anti-tumoral cell-mediated immune responses. We studied the in vitro proliferative responses and cytokine production in T cell cultures after 2 stimulations with autologous DC loaded with tumor lysates derived from glioblastoma multiforme (GBM) cells in the presence of recombinant interleukin (rIL)-6/rIL-12 in the first, and rIL-2/rIL-7 in the second stimulation. After the second stimulation, T cells were co-cultured with glioblastoma (GBM) cells and tumor growth suppression by T cells was assessed using a MTT assay. Although loaded DC induced a significant shift towards T helper cell type 1 (Th1) cytokine production as compared to unloaded DC, persistent interleukin (IL)-10 production by T cells both at the end of 2 stimulations with loaded DC and during the effector phase was also required for their tumor suppressive activity. A stronger glioma growth suppressive activity by T cells stimulated with tumor lysate-loaded DC than by control T cells, cultured with unloaded DC, was seen only if the relative IL-10 production after two stimulations with loaded DC was at least 40% of the IL-10 production after two stimulations with unloaded DC. If less than 40% IL-10 was produced in the experimental condition compared to the control condition, T cells also lost their tumor growth suppressive activity. Addition of rIL-10 during stimulation increased the suppressive activity on tumor cell viability and interferon (IFN)-gamma production by T cells that showed Th1 response upon stimulation with loaded DC. The data point towards the production of both IFN-gamma and IL-10 by responding effector T cells, and towards an immune modulatory rather than immune suppressive role of IL-10 to generate anti-tumoral effector T cells against GBM.

Production of IL-10 by alloreactive sibling donor cells and its influence on the development of acute GVHD

Graft-versus-host disease (GVHD) is a major complication of allogeneic hematopoietic stem cell transplantation. Pretransplant conditioning regimes cause release of proinflammatory cytokines that stimulate alloreactive donor T cells to attack recipient tissues. IL-10 has been shown to directly downregulate CD4+ T cells by suppressing IL-2 secretion and a critical role played by regulatory T cells has been demonstrated in animal models. One defining cytokine profile for regulatory T cells is the production of IL-10. Release of specific cytokines (IL-10, IL-4 and IFN-gamma) was detected using ELISPOT technology, following stimulation of donor peripheral blood mononuclear cells by recipient (human leukocyte antigen-matched sibling) alloantigen or by mitogen. Correlation between the frequency of cytokine-releasing cells and the development of acute GVHD was investigated. A high frequency of donor cells producing IL-10 in response to recipient alloantigen stimulation correlated with absence of acute GVHD after bone marrow transplant (BMT), while low frequency was strongly associated with severe GVHD. This study presents strong evidence that estimating the frequency of donor alloreactive cells producing IL-10 in response to recipient antigens will provide valuable information prior to BMT regarding potential transplant outcome.

Depressed type 1 cytokine synthesis by superantigen-activated CD4+ T cells of women with human papillomavirus-related high-grade squamous intraepithelial lesions

Carcinoma of the cervix is causally related to infection with the human papillomavirus (HPV), and T cells play a pivotal role in the immune response of the host to rid itself of HPV infection. Therefore, we assessed the T-cell function of women with HPV-related cervical neoplasia against a superantigen, Staphylococcus enterotoxin B (SEB). Each woman provided a cervical brush specimen for HPV DNA testing and Papanicolaou (Pap) smears for the staging of cervical lesions. They also provided a blood specimen for determination of the ability of CD4(+) T and CD8(+) T cells to synthesize Th1 (interleukin-2 [IL-2], gamma interferon [IFN-gamma], and tumor necrosis factor alpha [TNF-alpha]) and Th2 (IL-10) cytokines in response to activation with SEB. Compared with control subjects with self-attested negative Pap smears, women with high-grade squamous intraepithelial lesions (HSIL) had significantly lower percentages of activated CD4(+) T cells that produced IL-2 (P = 0.045), IFN-gamma (P = 0.040), and TNF-alpha (P = 0.015) and a significantly lower percentage of activated CD8(+) T cells that produced IL-2 (P < 0.01). These data indicate that women with HPV-related cervical HSIL show a decrease in Th1 cytokine production by activated CD4(+) T cells and suggested that compromised T-helper functions may negatively impact the function of cytotoxic CD8(+) T cells.

Allergen-specific T cells from birch-pollen-allergic patients and healthy controls differ in T helper 2 cytokine and in interleukin-10 production

BACKGROUND

T helper (Th)2 cells play an important role in the development of IgE-mediated diseases, with local overproduction of Th2 cytokines (IL-4, IL-5 and IL-13) at the site of allergic inflammation. Furthermore, IL-10 has been suggested to play a modulatory role in the induction and maintenance of allergen-specific tolerance in human atopic diseases.

AIM

We studied whether circulating allergen-specific Th2 cells persist outside the season of exposure in patients mono-sensitized to birch pollen and whether healthy control individuals also have allergen-specific Th2 cells. We also studied whether IL-10-producing allergen-specific T cells can be found in circulation either in healthy controls or in allergic patients.

METHODS

Blood was drawn outside the birch-pollen season from 15 birch-pollen-allergic patients, with seasonal respiratory symptoms and with (n=12) or without (n=3) oral allergy syndrome, and from 10 matched healthy controls. Peripheral blood mononuclear cells (PBMCs) were stimulated in vitro with recombinant Bet v 1 allergen, control antigen tetanus toxoid (TT) and anti-CD3/CD80. In part of the cultures, rIL-4 was added in order to reinforce the allergen-specific Th2 cell responses.

RESULTS

In the presence of rBet v 1, T cells from allergic patients, but not from healthy controls, produced IL-4, IL-5 and IL-13. IL-5 production by patients' T cells was further enhanced by adding more IL-4. In contrast, rBet v 1 together with IL-4-induced significant IL-10 production in control subjects but not in patients. Both Th1 and Th2 cytokines were equally induced by polyclonal stimulation in allergic patients and controls, but in the presence of IL-4, polyclonally induced IL-10 production was lower in the patient group.

CONCLUSION

rBet v 1-specific Th2 cells circulate outside the season of exposure in the blood of birch-pollen-allergic subjects but not in healthy controls. Allergen-specific T cells were also demonstrated in controls but these cells produce IL-10 when stimulated with rBet v 1 in the presence of IL-4. Our data reveal a different allergen-induced cytokine profile in birch-pollen-allergic patients vs. controls, and suggest that a regulatory mechanism involving IL-4-induced allergen-specific IL-10 production might be defective in allergic subjects.

Bisphenol A promotes IL-4 production by Th2 cells

BACKGROUND

It has been proposed that estrogen plays an important role in modulating the Th1/Th2 cytokine balance. From this viewpoint, chemicals with estrogenic responses were expected to possess similar immunoregulatory roles which have not been defined to date. To address this, we studied the effects of one of the estrogenic chemicals, bisphenol A (BPA), on the in vitro production of Th1 and Th2 cytokines.

METHODS

Mesenteric lymph node cells from Trichinella spiralis (Ts)-infected mice were incubated with serialfold dilutions of BPA under stimulation with Ts antigen. The Th2 cytokine production in the supernatant was determined by ELISA. The Th2 cytokine production by mesenteric lymph node cells from Ts-infected mice inoculated orally with BPA was compared with that of uninoculated mice infected with Ts.

RESULTS

The antigen-stimulated interleukin (IL)-4 production by Th2-dominant mesenteric lymph node cells from Ts-infected mice increased significantly by addition of 3 microM of BPA. The IL-5 production was not affected. The production of IL-4, but not that of IL-5, by splenocytes of Th2-skewed Leishmania major-infected BALB/c mice increased at concentrations of 3 and 10 microM of BPA. However, the interferon gamma production was not affected by BPA in Th1-skewed L. major-infected C57BL/6 mice. The production of IL-4 and IL-10, but not that of IL-13, markedly increased in Ts-infected mice inoculated orally with BPA.

CONCLUSIONS

We demonstrated that the IL-4 production was increased both in vitro and in vivo by treatment with BPA. This suggests that BPA might cause allergic diseases by stimulating the IL-4 production by Th2 cells.

Sensitivity of Whole-Blood T Lymphocytes in Individual Patients to Tacrolimus (FK 506): Impact of Interleukin-2 mRNA Expression as Surrogate Measure of Immunosuppressive Effect

Background: To optimize immunosuppressive treatment in individual transplant patients, functional measurements of the effects of tacrolimus (FK 506) are of clinical importance. Previous investigations have demonstrated the occurrence of tacrolimus-resistant production of interleukin-2 (IL-2) in vitro, which may explain in part why rejection episodes are still a frequent problem despite attainment of therapeutic blood concentrations and HLA matching. However, an adequate surrogate marker to define the tacrolimus response in individual patients has not been established.

Methods: We investigated the immunosuppressive effects of tacrolimus on anti-CD3/anti-CD28 T-cell costimulation in a human whole-blood assay, analyzing T-cell proliferation, activation marker expression (CD25, CD69), IL-2 protein expression, and cytokine mRNA expression in vitro (n = 11 healthy individuals). We also quantified IL-2 mRNA expression in patients undergoing tacrolimus (n = 4) or cyclosporin A (CsA; n = 4) monotherapy before ex vivo living-donor kidney transplantation.

Results: T-cell proliferation; CD25, CD69, and IL-2 concentrations; and IL-4 mRNA were significantly decreased in vitro. In contrast, cytokine mRNA profiles revealed variable tacrolimus sensitivity. Whole-blood samples from 3 of 11 healthy individuals demonstrated marked suppression of IL-2 mRNA expression (&gt;50%) when tacrolimus was administered in vitro. When CsA was added to whole-blood cultures, the influence on IL-2 mRNA expression was comparable to that of tacrolimus in 9 of 11 individuals. Two individuals responded conversely, indicating that differences in the in vitro response to tacrolimus and CsA among individuals may be attributable to potential heterogeneity in the involvement of the CD28 pathway. Kinetic profiles of IL-2 mRNA expression also revealed individually distinct degrees of calcineurin inhibitor sensitivity in patients undergoing tacrolimus or CsA monotherapy before living-donor kidney transplantation.

Conclusions: Our results suggest an individual degree of calcineurin inhibitor sensitivity of activated whole-blood lymphocytes based on IL-2 mRNA expression. Our approach is potentially valuable for identifying transplant patients in whom IL-2 mRNA expression is unaffected or even enhanced after initiation of immunosuppressive therapy. Such individuals may be less sensitive to the immunosuppressive agent and therefore at increased risk of transplant rejection. Prospective studies are necessary to determine the correlation of IL-2 mRNA expression with the clinical risk of transplant rejection.

Immunological mechanisms in specific immunotherapy

Specific immunotherapy (SIT) represents the only curative treatment of allergy and is, therefore, of particular interest for immunological and pharmacological research. The current understanding of immunological mechanisms underlying SIT focuses on regulatory T cells (T regs), which balance Th1 and Th2 effector functions. This ensures that allergens are recognized, but tolerated by the immune system. There is clear evidence that SIT restores the disturbed balance of T regs and effector cells in allergic patients. Current efforts are focused to improve SIT regimens to make them more applicable in atopy and asthma. The current review provides an overview on the mechanisms of SIT and possible adjuvant treatment strategies on the background of the T reg concept.

Review of the properties and mechanisms of action of cyclosporine with an emphasis on dermatological therapy in dogs, cats and people

Cyclosporine is being increasingly used in veterinary medicine. It is a potent suppressor of T cell induction and proliferation, and has a wide variety of anti-inflammatory and antiproliferative effects, downregulating effects on antigen presentation, and variable effects on parasites. This paper reviews its properties and mechanisms of action with particular reference to its use in the treatment of dermatological conditions in dogs, cats and people.

Review of the pharmacokinetics, interactions and adverse reactions of cyclosporine in people, dogs and cats

Cyclosporine is being increasingly used in veterinary medicine. Oral formulations of the drug have found many therapeutic uses, but topical formulations have met with only limited success, probably owing to their poor penetration through the stratum corneum. The concurrent use of ketoconazole to inhibit cyclosporine metabolism has been shown to reduce the required dose and hence the cost of cyclosporine therapy. In human medicine, adverse reactions to the drug, especially nephrotoxicity, are common but in dogs given the commonly used oral dose of 5 mg/kg per day there have been few adverse reactions. However, no toxicity studies lasting longer than 12 months have been carried out in this species. This paper reviews the pharmacokinetics, drug and procedural interactions, contraindications and the adverse reactions to cyclosporine, with particular reference to its use in the treatment of dermatological conditions in dogs, cats and people.

Impaired secretion of IL-10 by T cells from patients with common variable immunodeficiency--involvement of protein kinase A type I

Common variable immunodeficiency (CVID) is a heterogeneous group of B cell deficiency syndromes. T cell abnormalities are present in a high proportion of patients with CVID, suggesting impaired T cell-mediated stimulation of B cells. Based on the importance of IL-10 for B cell function and the involvement of the cAMP/protein kinase A type I (PKAI) system in IL-10 synthesis, we examined IL-10 secretion in T cells from CVID patients and controls, particularly focusing on possible modulatory effects of the cAMP/PKAI system. Our main findings were: 1) anti-CD3 and anti-CD3/anti-CD28 activated T cells from CVID patients secreted less IL-10 than healthy controls. This defect was not related to varying proportions of T cell subsets (e.g., CD4(+)/CD8(+), CD45RA(+)/RO(+), or CD28(-) T cells); 2) PKAI activation through the cAMP agonist 8-CPT-cAMP markedly inhibited IL-10 secretion from T cells through CD3 and CD28 activation in both patients and controls, but the sensitivity for cAMP-dependent inhibition was increased in CVID; 3) selective PKAI inhibition by Rp-8-Br-cAMPS markedly increased IL-10 secretion in anti-CD3 and anti-CD3/anti-CD28-stimulated T cells in both patients and controls. Even at the lowest concentrations of Rp-8-Br-cAMPS, IL-10 secretion in CVID patients reached levels comparable to those in controls. Our findings suggest impaired secretion of IL-10 by T cells from CVID patients, suggesting a possible link between T cell deficiency and impaired B cell function in CVID. The involvement of the cAMP/PKAI system in this defect suggests a novel target for therapeutic immunomodulation in CVID.

The complementary roles of deletion and regulation in transplantation tolerance

Neonatal tolerance of alloantigens was described in mice nearly half a century ago, but unfortunately, the translation of these early findings into the clinical arena proved to be much more challenging than was first anticipated. However, the past decade has seen considerable progress in our understanding of the mechanisms that contribute to transplantation tolerance in experimental models. This review outlines our current understanding of the mechanisms of allograft tolerance, emphasizing the complementary roles of deletion and regulation of alloreactive T cells.

Murine Peyer's patches favor development of an IL-10-secreting, regulatory T cell population

Peyer's patches (PP) are believed to be the principal sites for induction of tolerance to Ags from food and commensal flora, yet the phenotype of T cells activated within the PP is largely unexplored. We hypothesize that exposure to Ags within the PP promotes differentiation of T cells with immunoregulatory functions. Cytokine production and cell surface marker expression of murine PP mononuclear cells (MC) are compared with those from mesenteric lymph nodes and peripheral lymph nodes (PLN). In response to stimulation through the TCR/CD3 complex, PP MC exhibit vigorous proliferation, modest production of IL-2, and significantly elevated synthesis of IL-10. Exogenous IL-12 enhances both IL-10 and IFN-gamma secretion by activated PP MC. Cell surface marker analysis reveals that PP T cells consist of activated and memory subpopulations compared with the predominantly naive T cells identified in the PLN and mesenteric lymph nodes. Upon stimulation, only CD45RB(low)CD4(+) PP T cells produce IL-10, whereas secretion of IL-2, IL-4, and IFN-gamma was not detected. Furthermore, PP MC, but not PLN MC, stimulated through the TCR/CD3 complex suppress proliferation of purified PLN T cells in vitro, evidence for a regulatory function among PP lymphocytes. We conclude that PP favor differentiation of an IL-10-producing, regulatory CD45RB(low)CD4(+) T cell population and that inhibition of T cell proliferation by activated PP MC may reflect regulatory activity consistent with T regulatory cells.

Effects of co-stimulation by CD58 on human T cell cytokine production: a selective cytokine pattern with induction of high IL-10 production

CD58 is the ligand for the CD2 molecule on human T cells and has been shown to provide a co-stimulatory signal for T cell activation. However, its physiological role is still unclear. We studied the effects of co-stimulation by CD58 on the production of T(h)1-type (IL-2- and IFN-gamma) or T(h)2 type (IL-4, IL-5 and IL-10) cytokines in an in vitro culture system of purified human T cells with CD58-transfected P815 cells and with anti-CD3 as the primary stimulus. Co-stimulation of T cells by CD58 potently induced IL-10 and IFN-gamma production (at the protein and at the mRNA level), and transforming growth factor-ss production (at the mRNA level), comparable to what can be found in CD80 co-stimulated T cell cultures. In contrast, we found low to absent IL-2, IL-4, IL-5, IL-13 and tumor necrosis factor-alpha production after CD58 co-stimulation, and this was not due to suppressive effects of endogenously produced IL-10. CD80 co-stimulation strongly induced all these cytokines. Intracellular staining for cytokine expression revealed the existence of a T cell subpopulation induced by CD58 co-stimulation to produce both IFN-gamma and IL-10. We furthermore found that the selective cytokine profile induced by CD58 co-stimulation is further accentuated by rIL-12 and by rIFN-alpha. Using cyclosporin A as an inhibitor of the calcineurin enzyme, we could show that production of all cytokines in this system is calcium dependent. CD58 co-stimulation thus induces a cytokine pattern corresponding to that described for T regulatory (T(r)) 1 cells and to the pattern reported to be induced by the newly identified B7 family member, B7-H1.