Biomedical subjects

O M Zack Howard

Publications and source records attributed to O M Zack Howard.

At least 19 recordsLinked to original sources

PubMed2006

Brugia malayi asparaginyl-transfer RNA synthetase induces chemotaxis of human leukocytes and activates G-protein-coupled receptors CXCR1 and CXCR2.

Background. Lymphatic filariasis is a chronic human parasitic disease in which the parasites repeatedly provoke acute and chronic inflammatory reactions in the host bloodstream and lymphatics. Excretory-secretory products derived from filariae are believed to play an important role in the development of associated immunologic conditions; however, the specific mechanisms involved in these changes are not well understood. Recently, human cytoplasmic aminoacyl-transfer (t) RNA synthetases, which are autoantigens in idiopathic inflammatory myopathies, were shown to activate chemokine receptors on T lymphocytes, monocytes, and immature dendritic cells by recruiting immune cells that could induce innate and adaptive immune responses. Filarial (Brugia malayi) asparaginyl-tRNA synthetase (AsnRS) is known to be an immunodominant antigen that induces strong human immunoglobulin G3 responses.Methods. Recombinant B. malayi AsnRS was used to perform cellular function assays--for example, chemotaxis and kinase activation assays.Results. Unlike human AsnRS, parasite AsnRS is chemotactic for neutrophils and eosinophils. Recombinant B. malayi AsnRS but not recombinant human AsnRS induced chemotaxis of CXCR1 and CXCR2 single-receptor-transfected HEK-293 cell lines, blocked CXCL1-induced calcium flux, and induced mitogen-activated protein kinase.Conclusions. Our findings suggest that a filarial parasite chemoattractant protein may contribute to the development of chronic inflammatory disease and that chemokine receptors may be therapeutic targets to ameliorate parasite-induced pathology.

Animals↗

PubMed2006

Pertussis toxin as an adjuvant suppresses the number and function of CD4+CD25+ T regulatory cells.

We observed a remarkable reduction in the frequency and immunosuppressive activity of splenic CD4+CD25+ T cells in C57BL/6 mice with MOG33-55-induced experimental autoimmune encephalomyelitis (EAE). Our study revealed that pertussis toxin (PTx), one component of the immunogen used to induce murine EAE, was responsible for down-regulating splenic CD4+CD25+ cells. Treatment of normal BALB/c mice with PTx in vivo reduced the frequency, suppressive activity and FoxP3 expression by splenic CD4+CD25+ T cells. However, PTx treatment did not alter the expression of characteristic phenotypic markers (CD45RB, CD103, GITR and CTLA-4) and did not increase the expression of CD44 and CD69 by the residual splenic and lymph node CD4+CD25+ T cells. This property of PTx was attributable to its ADP-ribosyltransferase activity. PTx did not inhibit suppressive activity of purified CD4+CD25+ T regulatory (Treg) cells in vitro, but did so in vivo, presumably due to an indirect effect. Although the exact molecular target of PTx that reduces Treg activity remains to be defined, our data suggests that alteration of both distribution and function of splenic immunocytes should play a role. This study concludes that an underlying cause for the immunological adjuvanticity of PTx is down-regulation of Treg cell number and function.

Adjuvants, Immunologic↗

PubMed2006

Glucocorticoid amplifies IL-2-dependent expansion of functional FoxP3(+)CD4(+)CD25(+) T regulatory cells in vivo and enhances their capacity to suppress EAE.

IL-2 is crucial for the production of CD4(+)CD25(+) T regulatory (Treg) cells while important for the generation of effective T cell-mediated immunity. How to exploit the capacity of IL-2 to expand Treg cells, while restraining activation of T effector (Teff) cells, is an important and unanswered therapeutic question. Dexamethasone (Dex), a synthetic glucocorticoid steroid, has been reported to suppress IL-2-mediated activation of Teff cells and increase the proportion of Treg cells. Thus, we hypothesized that glucocorticoids may be useful as costimulants to amplify IL-2-mediated selective expansion of Treg cells. We show in this study that short-term simultaneous administration of Dex and IL-2 markedly expanded functional suppressive Foxp3(+)CD4(+)CD25(+) T cells in murine peripheral lymphoid tissues. In a myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis (EAE) mouse model, we observed that splenic CD4(+)CD25(+) T cells failed to suppress the proliferation of CD4(+)CD25(-) T cells. Pretreatment with Dex/IL-2 remarkably increased the proportion of CD4(+)FoxP3(+) cells and partially restored the function of splenic CD4(+)CD25(+) T cells, and inhibited the development of EAE. Therefore, the combination of glucocorticoid and IL-2, two currently used therapeutics, may provide a novel approach for the treatment of autoimmune diseases, transplant rejection and graft-vs.-host disease.

Animals↗

PubMed2006

The scaffold protein Cybr is required for cytokine-modulated trafficking of leukocytes in vivo.

Trafficking and cell adhesion are key properties of cells of the immune system. However, the molecular pathways that control these cellular behaviors are still poorly understood. Cybr is a scaffold protein highly expressed in the hematopoietic/immune system whose physiological role is still unknown. In vitro studies have shown it regulates LFA-1, a crucial molecule in lymphocyte attachment and migration. Cybr also binds cytohesin-1, a guanine nucleotide exchange factor for the ARF GTPases, which affects actin cytoskeleton remodeling during cell migration. Here we show that expression of Cybr in vivo is differentially modulated by type 1 cytokines during lymphocyte maturation. In mice, Cybr deficiency negatively affects leukocytes circulating in blood and lymphocytes present in the lymph nodes. Moreover, in a Th1-polarized mouse model, lymphocyte trafficking is impaired by loss of Cybr, and Cybr-deficient mice with aseptic peritonitis have fewer cells than controls present in the peritoneal cavity, as well as fewer leukocytes leaving the bloodstream. Mutant mice injected with Moloney murine sarcoma/leukemia virus develop significantly larger tumors than wild-type mice and have reduced lymph node enlargement, suggesting reduced cytotoxic T-lymphocyte migration. Taken together, these data support a role for Cybr in leukocyte trafficking, especially in response to proinflammatory cytokines in stress conditions.

Animals↗

PubMed2005

Human tumor antigen MUC1 is chemotactic for immature dendritic cells and elicits maturation but does not promote Th1 type immunity.

The immunostimulatory outcome of the interactions of many pathogens with dendritic cells (DCs) has been well characterized. There are many fewer examples of similar interactions between DCs and self-molecules, especially the abnormal self-proteins such as many tumor Ags, and their effects on DC function and the immune response. We show that human epithelial cell Ag MUC1 mucin is recognized in its aberrantly glycosylated form on tumor cells by immature human myeloid DCs as both a chemoattractant (through its polypeptide core) and a maturation and activation signal (through its carbohydrate moieties). On encounter with MUC1, similar to the encounter with LPS, immature DCs increase cell surface expression of CD80, CD86, CD40, and CD83 molecules and the production of IL-6 and TNF-alpha cytokines but fail to make IL-12. When these DCs are cocultured with allogeneic CD4+ T cells, they induce production of IL-13 and IL-5 and lower levels of IL-2, thus failing to induce a type 1 response. Our data suggest that, in vivo in cancer patients, MUC1 attracts immature DCs to the tumor through chemotaxis and subverts their function by negatively affecting their ability to stimulate type 1 helper T cell responses important for tumor rejection.

Amino Acid Sequence↗

PubMed2005

Negative regulation of CXCR4-mediated chemotaxis by the lipid phosphatase activity of tumor suppressor PTEN.

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN), a multifunctional tumor suppressor, has been shown to play a regulatory role in cell migration. Dictyostelium discoideum cells lacking PTEN exhibited impaired migration toward chemoattractant gradients. In the present study, we investigated the involvement of PTEN in chemotaxis of mammalian cells by examining PTEN-null Jurkat T cells. We observed that, in contrast to observations made in D discoideum, PTEN-null Jurkat T cells exhibited potent chemotactic responses to the chemokine stromal cell-derived factor 1alpha (SDF-1alpha), indicating that PTEN was not requisite for CXC chemokine receptor 4 (CXCR4)-mediated chemotaxis of Jurkat cells. Conversely, reconstitution of PTEN in Jurkat cells by using a tetracycline (Tet-on)-inducible expression system down-regulated CXCR4-mediated chemotaxis. Furthermore, we established the lipid phosphatase activity of PTEN as essential for its inhibitory effect on chemotaxis. In addition, using PTEN-expressing T-cell lines and primary T cells, we demonstrated that down-regulation of PTEN expression with vector-based small interfering RNAs (siRNAs) enhanced CXCR4-mediated chemotaxis. Based on these results, we conclude that PTEN expression negatively regulates chemotaxis of lymphoid mammalian cells via its lipid phosphatase activity. Our findings may account for the reported increase in metastatic activity of PTEN-null tumor cells.

Animals↗

PubMed2005

Triptolide, a constituent of immunosuppressive Chinese herbal medicine, is a potent suppressor of dendritic-cell maturation and trafficking.

Triptolide (TPT) is a chemically defined, potent immunosuppressive compound isolated from an anti-inflammatory Chinese herbal medicine. TPT has been reported to inhibit autoimmunity, allograft rejection, and graft-versus-host disease (GVHD), and its efficacy was previously attributed to the suppression of T cells. Since dendritic cells (DCs) play a major role in the initiation of T-cell-mediated immunity, we studied the effects of TPT on the phenotype, function, and migration of human monocyte-derived DCs. TPT treatment, over a pharmacologic concentration range, inhibited the lipopolysaccharide (LPS)-induced phenotypic changes, characteristic of mature DCs and the production of interleukin-12p70 (IL-12p70). Consequently, the allostimulatory functions of DCs were impaired by TPT treatment. Furthermore, the calcium mobilization and chemotactic responses of LPS-stimulated DCs to secondary lymphoid tissue chemokine (SLC)/CC chemokine ligand 21 (CCL21) were significantly lower in TPT-treated than untreated DCs, in association with lower chemokine receptor 7 (CCR7) and higher CCR5 expression. Egress of Langerhans cells (LCs) from explanted mouse skin in response to macrophage inflammatory protein-3beta (MIP-3beta)/CCL19 was arrested by TPT. In vivo administration of TPT markedly inhibited hapten (fluorescein isothiocyanate [FITC])-stimulated migration of mouse skin LCs to the draining lymph nodes. These data provide new insight into the mechanism of action of TPT and indicate that the inhibition of maturation and trafficking of DCs by TPT contributes to its immunosuppressive effects.

Animals↗

PubMed2005

Formylpeptide receptor FPR and the rapid growth of malignant human gliomas.

BACKGROUND: The formylpeptide receptor (FPR) is a G-protein-coupled receptor (GPCR) that mediates chemotaxis of phagocytic leukocytes induced by bacterial peptide N-formyl-methionyl-leucyl-phenylalanine (fMLF). We previously showed that selected human glioma cell lines also express functional FPR. We therefore investigated the relationship between FPR expression and the biologic behavior of glioma cells. METHODS: Expression and function of FPR in the human glioblastoma cell line U-87 were examined by reverse transcription-polymerase chain reaction (RT-PCR) and chemotaxis assays, respectively. FPR protein expression was detected in specimens from 33 human primary gliomas by immunohistochemistry. FPR short interfering (si) RNA was used to block FPR expression in U-87 cells. Cell proliferation was assessed by measuring DNA synthesis. Xenograft tumor formation and growth were measured in nude mice. Endogenous FPR agonist activity released by necrotic tumor cells was assessed by measuring FPR activation in an FPR-transfected basophil leukemia cell line and live U-87 cells. Vascular endothelial growth factor (VEGF) mRNA was assessed by RT-PCR, and VEGF protein was assessed by enzyme-linked immunosorbent assay. All statistical tests were two-sided. RESULTS: FPR was selectively expressed by the highly malignant human glioblastoma cell line U-87 and most primary grade IV glioblastomas multiforme and grade III anaplastic astrocytomas. U-87 cells responded to the FPR agonist fMLF by chemotaxis (i.e., increased motility), increased cell proliferation, and increased production of VEGF protein. FPR siRNA substantially reduced the tumorigenicity of U-87 cells in nude mice (38 days after implantation, mean tumor volume from wild-type U-87 cells = 842 mm3, 95% confidence interval [CI] = 721 to 963 mm3; and from FPR-siRNA transfected U-87 cells = 225 mm3, 95% CI = 194 to 256 mm3; P = .001). Necrotic glioblastoma cells released a factor(s) that activated FPR in live U-87 cells. CONCLUSIONS: FPR is expressed by highly malignant human glioma cells and appears to mediate motility, growth, and angiogenesis of human glioblastoma by interacting with host-derived agonists. Thus, FPR may represent a molecular target for the development of novel antiglioma therapeutics.

Animals↗

PubMed2005

BALB/c mice have more CD4+CD25+ T regulatory cells and show greater susceptibility to suppression of their CD4+CD25- responder T cells than C57BL/6 mice.

Increasing evidence indicates that CD4(+)CD25(+) T regulatory (Treg) cells control a wide spectrum of immune responses. The initial identification of CD4(+)CD25(+) Treg cell as a "professional suppressor" was based on observations made in BALB/c mice. This mouse strain is well known to preferentially develop T helper cell type 2 responses, to be more susceptible to intracellular parasite infection, to have a higher tumor incidence, and to be more resistant to the induction of autoimmune diseases, as compared with C57BL/6 (B6) mice. We therefore decided to compare Treg cell function of B6 and BALB/c mice. We observed that the frequency of CD4(+)CD25(+) T cells in the thymus and peripheral lymphoid organs of BALB/c mice was higher than in B6 mice. CD4(+)CD25(+) Treg cells from both mouse strains shared similar phenotypic properties, including expression of characteristic immunological markers and hyporesponsiveness to T cell receptor cross-linking and in their capacity to suppress proliferation of BALB/c CD4(+)CD25(-) T responder (Tres) cells. However, CD4(+)CD25(-) Tres cells from B6 mice were notably less susceptible to suppression by CD4(+)CD25(+) Treg cells from either mouse strain. Our data suggest that the number and the level of suppression of CD4(+)CD25(+) Treg cells for CD4(+)CD25(-) Tres cells may be dictated by genetic background. Our data also suggest that differences in the CD4(+)CD25(+) Treg cell number and the susceptibility of CD4(+)CD25(-) Tres cells may, at least in part, account for the differences in immune response between B6 and BALB/c strains of mice.

Animals↗

PubMed2005

Autoantigens signal through chemokine receptors: uveitis antigens induce CXCR3- and CXCR5-expressing lymphocytes and immature dendritic cells to migrate.

We tested the hypothesis that interaction between autoantigens and chemoattractant receptors may be an important step in the development of autoimmunity. The retinal autoantigens S-antigen (S-Ag) and interphotoreceptor retinoid binding protein (IRBP) can induce autoimmune uveitis in rodent models. We evaluated the chemotactic activity of S-Ag and IRBP and found that both induced migration of human and mouse immature dendritic cells (iDCs) and lymphocytes, but not neutrophils, monocytes, or mature DCs. Cross-desensitization studies and single-receptor transfected cells revealed that subfamily of alpha chemokine receptors CXCR5 and CXCR3 mediated the chemotactic effect of IRBP, while only CXCR3 was required for the chemotactic response to S-Ag. Examination of the relationships between chemoattraction and the ability to elicit pathology at the protein or peptide levels in the mouse uveitis model revealed dissociation of the capacity to induce uveitis, lymphocyte proliferation, and chemoattraction. These studies suggest that IRBP and S-Ag can initiate innate and, in sensitive individuals, adaptive immune response by attracting iDCs and T and B cells expressing CXCR3 and CXCR5.

Arrestin↗

PubMed2005

Triptolide attenuates endotoxin- and staphylococcal exotoxin-induced T-cell proliferation and production of cytokines and chemokines.

Proinflammatory cytokines mediate the toxic effects of superantigenic staphylococcal exotoxins (SE) and bacterial lipopolysaccharide (LPS). Triptolide, an oxygenated diterpene derived from a traditional Chinese medicinal herb, Tripterygium wilfordii, inhibited SE-stimulated T-cell proliferation (by 98%) and expression of interleukin 1beta, interleukin 6, tumor necrosis factor, gamma interferon, monocyte chemotactic protein 1, macrophage inflammatory protein (MIP)-1alpha, and MIP-1beta by human peripheral blood mononuclear cells (PBMC). It also blocked the production of these cytokines and chemokines by LPS-stimulated PBMC in a dose-dependent manner. These results suggest that triptolide has potent immunosuppressive effects even counteracting the effects of superantigens and LPS. It also may be therapeutically useful for mitigating the pathogenic effects of these microbial products by downregulating the signaling pathways activated by both bacterial exotoxins and endotoxins.

Bacterial Toxins↗

PubMed2005

Autoantigens act as tissue-specific chemoattractants.

We have investigated the chemoattractant properties of self-antigens associated with autoimmune diseases and solid tumors. Many autoantigens induced leukocyte migration, especially by immature dendritic cells (iDC) by interacting with various chemoattractant Gi-protein-coupled receptors (GiPCR). Our initial observation that myositis-associated autoantigens, histidyl-tRNA synthetase and asparaginyl-tRNA synthetase, were chemotactic for CC chemokine receptor 5 (CCR5)- and CCR3-expressing leukocytes, while other nonautoantigenic aminoacyl-tRNA synthesases were not, suggested that only self-antigens capable of interacting with receptors on antigen-presenting cells were immunogenic. We next determined that self-antigens associated with autoimmune diseases, e.g., multiple sclerosis or experimental autoimmune encephalomyelitis, type I diabetes, scleroderma, systemic lupus erythematosus, autoimmune uveitis, or experimental autoimmune uveitis (EAU), were chemotactic for GiPCR expressed by iDC. The majority of autoantigens were DC chemoattractants at 10-100 ng/ml, but did not induce DC maturation until they reached 1000-fold higher concentrations. Interphotoreceptor retinoid-binding protein and retinal arrestin (S-antigen) are targets of autoantibodies in human uveitis and are chemotactic for CXC chemokine receptor 5 (CXCR5)- and/or CXCR3-expressing iDC. However, although S-antigen does not induce EAU in wild-type mice, it is nevertheless a chemoattractant for murine iDC. These unexpected observations suggested that the chemotactic activity of these tissue-specific self-antigens could be involved in promotion of tissue repair and restoration. Thus, the primary role of autoantigens may be to alert the immune system to danger signals from invaded and damaged tissues to facilitate repair, and autoimmune responses subsequently develop only in subjects with impaired immunoregulatory function.

Animals↗

PubMed2004

Human ribonuclease A superfamily members, eosinophil-derived neurotoxin and pancreatic ribonuclease, induce dendritic cell maturation and activation.

A number of mammalian antimicrobial proteins produced by neutrophils and cells of epithelial origin have chemotactic and activating effects on host cells, including cells of the immune system. Eosinophil granules contain an antimicrobial protein known as eosinophil-derived neurotoxin (EDN), which belongs to the RNase A superfamily. EDN has antiviral and chemotactic activities in vitro. In this study, we show that EDN, and to a lesser extent human pancreatic RNase (hPR), another RNase A superfamily member, activates human dendritic cells (DCs), leading to the production of a variety of inflammatory cytokines, chemokines, growth factors, and soluble receptors. Human angiogenin, a RNase evolutionarily more distant to EDN and hPR, did not display such activating effects. Additionally, EDN and hPR also induced phenotypic and functional maturation DCs. These RNases were as efficacious as TNF-alpha, but induced a different set of cytokine mediators. Furthermore, EDN production by human macrophages could be induced by proinflammatory stimuli. The results reveal the DC-activating activity of EDN and hPR and suggest that they are likely participants of inflammatory and immune responses. A number of endogenous mediators in addition to EDN have been reported to have both chemotactic and activating effects on APCs, and can thus amplify innate and Ag-specific immune responses to danger signals. We therefore propose these mediators be considered as endogenous multifunctional immune alarmins.

Antigens, CD34↗

PubMed2004

Functional redundancy of the human CCL4 and CCL4L1 chemokine genes.

CCL4 and CCL4L1 are two CC chemokine genes located at chromosome 17q21 whose mature proteins differ at only a single amino acid. Abundant functional information exists for CCL4, however, CCL4L1 has only recently been recognized as a distinct gene, thus information describing it is wanting. The CCL4L1 protein was synthesized in Escherichia coli and compared with the CCL4 protein. Competitive binding studies using HEK-293/CCR5 cells produced comparable EC50 values for the two proteins. Similarly, chemotaxis assays with cells expressing CCR1, CCR3, or CCR5 revealed no substantial differences. CCL4L1 was somewhat more effective at inhibiting HIV-1 replication in PBMCs than was CCL4, however the difference was not statistically significant. These data combined with the observation of individual variation in CCL4L1 gene copy number [Eur. J. Immunol. 32 (2002) 3016, Genomics 83 (2004) 735] support the contention that the CCL4 and CCL4L1 proteins have redundant functions.

Amino Acid Sequence↗

PubMed2004

Selenium deficiency abrogates inflammation-dependent plasma cell tumors in mice.

The role of the micronutrient, selenium, in human cancers associated with chronic inflammations and persistent infections is poorly understood. Peritoneal plasmacytomas (PCTs) in strain BALB/c (C), the premier experimental model of inflammation-dependent plasma cell transformation in mice, may afford an opportunity to gain additional insights into the significance of selenium in neoplastic development. Here, we report that selenium-depleted C mice (n = 32) maintained on a torula-based low-selenium diet (5-8 micro g of selenium/kg) were totally refractory to pristane induction of PCT. In contrast, 11 of 26 (42.3%) control mice maintained on a selenium adequate torula diet (300 micro g of selenium/kg) and 15 of 40 (37.5%) control mice fed standard Purina chow (440 micro g of selenium/kg) developed PCT by 275 days postpristane. Abrogation of PCT was caused in part by the striking inhibition of the formation of the inflammatory tissue in which PCT develop (pristane granuloma). This was associated with the reduced responsiveness of selenium-deficient inflammatory cells (monocytes and neutrophils) to chemoattractants, such as thioredoxin and chemokines. Selenium-deficient C mice exhibited little evidence of disturbed redox homeostasis and increased mutant frequency of a transgenic lacZ reporter gene in vivo. These findings implicate selenium, via the selenoproteins, in the promotion of inflammation-induced PCT and suggest that small drug inhibitors of selenoproteins might be useful for preventing human cancers linked with chronic inflammations and persistent infections.

Animals↗

PubMed2004

Up-regulated expression and activation of the orphan chemokine receptor, CCRL2, in rheumatoid arthritis.

OBJECTIVE: Rheumatoid arthritis (RA) is a chronic inflammatory condition characterized by a cellular influx and destruction of the joint architecture. Chemokines characteristically regulate leukocyte recruitment and activation. Chemokine (CC motif) receptor-like 2 (CCRL2) is an orphan receptor with homology to other CC chemokine receptors. We undertook this study to examine CCRL2 expression in RA, cytokine regulation of expression, and the source of a putative ligand in an attempt to determine the role of this receptor during inflammation. METHODS: Expression of CCRL2 on joint-infiltrating leukocytes was examined by immunocytochemistry. In vitro studies evaluated CCRL2 expression in primary neutrophils using Northern and Western blotting and reverse transcriptase-polymerase chain reaction. HEK 293 cells expressing two splice variants of CCRL2 (HEK/CCRL2A or HEK/CCRL2B) were generated with a retroviral expression system, and their migration in response to fractions of synovial fluid (SF) from RA patients was examined using a 48-well chamber. RESULTS: CCRL2 expression was observed on all infiltrating neutrophils and on some macrophages obtained from the SF of 5 RA patients. In vitro studies of primary neutrophils revealed that CCRL2 messenger RNA (mRNA) was rapidly up-regulated following stimulation with lipopolysaccharide (1 microg/ml) or tumor necrosis factor (5 ng/ml). The mRNA for both CCRL2A and CCRL2B were expressed in cytokine-stimulated neutrophils. Cells expressing either of these splice variants migrated in response to a fraction of RA SF. CONCLUSION: CCRL2 expression is up-regulated on synovial neutrophils of RA patients. Inflammatory products present in the SF activate this receptor, indicating that CCRL2 is a functional receptor that may be involved in the pathogenesis of RA.

Aged↗

PubMed2004

Differential response of murine CD4+CD25+ and CD4+CD25- T cells to dexamethasone-induced cell death.

To evaluate the in vivo effect of immunosuppressive glucocorticoids on CD4+CD25+ T regulatory cells, we injected dexamethasone (Dex) into BALB/c mice. Administration of Dex enhanced the proportion of CD4+CD25+ cells and the ratio of CD4+CD25+ cells to CD4+CD25- cells in the lymphoid organs, especially in the thymus. This correlates with our in vitro observation that CD4+CD25+ T cells express higher levels of glucocorticoid receptor and Bcl-2, and are therefore more resistant to Dex-mediated cell death than CD4+CD25- T cells. Furthermore, IL-2 selectively protected CD4+CD25+ T cells from Dex-induced cell death, while IL-7 and IL-15 did not exert preferential protective effects. Dex-treated CD4+CD25+ T cells expressed higher levels of intracellular CTLA-4 and surface glucocorticoid-induced TNF receptor than fresh CD4+CD25+ T cells, but still failed to respond to TCR stimulation and inhibited proliferation of CD4+CD25- T cells. These results suggest that, in addition to suppressing cytokine transcription, Dex treatment is permissive for the survival of functional CD4+CD25+ T regulatory cells, and this property may contribute to the anti-inflammatory and immunosuppressive efficacy of glucocorticoids. Our data also suggest that selective protection of CD4+CD25+ T cell from apoptosis may constitute a role in immune tolerance for IL-2.

Animals↗

PubMed2004

Yin zi huang, an injectable multicomponent chinese herbal medicine, is a potent inhibitor of T-cell activation.

OBJECTIVES: The clinical efficacy of many multiherbal Traditional Chinese Medicines (TCM) is partially attributable to their immunoregulatory properties. In this study we evaluated the effect of eight commonly used, commercially available multiherbal Chinese medicines on T-cell activation. We focused on Yin Zhi Huang (YZH, an injectable herbal medicine commonly used for the treatment of liver diseases in China), because it was the most potent inhibitor of T-cell activation in our experimental system. The effects of 10 ingredient components of YZH were also evaluated. METHODS: [3H] thymidine incorporation assay was used to assess mouse T-cell proliferation after stimulation with latex beads coated with anti-CD3/CD28 antibodies. CD25, CD69, PD-1, and I-COS expression by purified mouse CD4+ T cells treated with plate-bound anti-CD3 antibody and soluble anti-CD28 antibody was analyzed by fluorescent-activated cell sorter (FACS). Cytokine/chemokine production by human peripheral blood mononuclear cells (PBMC) stimulated with staphylococcal enterotoxin B (SEB) was determined by enzyme-linked immunosorbent assay (ELISA). RESULTS: Among tested herbal medicines, YZH was the most potent inhibitor of T-cell activation. In splenocyte proliferation assays, the inhibitory effect of YZH was dose-dependent, with a 50% inhibition concentration (IC50) of 1:3200-1:1600. Ten (10) purified compounds found in YZH were evaluated for their activity. Among them, ursolic acid (1-10 micromol), luteolin (1-10 micromol), baicalein (1-10 micromol), scopran (5-50 micromol), and crocin (5-50 micromol), exhibited dose-dependent inhibition. YZH also inhibited CD25, CD69, PD-1, and ICOS expression by stimulated mouse CD4+ T cells. In human PBMCs, YZH inhibited SEB-stimulated cytokine (interleukin [IL]-1, IL-2, IL-6, tumor necrosis factor[TNF]-alpha, interferon [IFN]-gamma) and chemokine (IP-10, MCP-1, MIP-1alpha and MIP-1beta) production in a dose-dependent manner. CONCLUSION: Our data show for the first time that YZH is a potent inhibitor of T-cell activation, and this property may be the major mechanism underlying the clinical efficacy of YZH. Our experimental results pave the way for identification of active component(s) and/or analysis of synergistic/additive effect of a YZH ingredient in future studies.

Animals↗