Increase In Proportion Of CD4 Research Articles

High-Dose IV Administration of Rasburicase Suppresses Anti-rasburicase Antibodies, Depletes Rasburicase-Specific Lymphocytes, and Upregulates Treg Cells.

Therapeutic proteins can be potent agents for treating serious diseases, but in many patients these proteins provoke antibody responses that blunt therapeutic efficacy. Intravenous administration of high doses of some proteins induces immune tolerance, but the mechanisms underlying this effect are poorly understood. As a model to study tolerance induction in mice, we used rasburicase, a commercial recombinant uricase used for the treatment of hyperuricemia. Intraperitoneal (i.p.) injection of rasburicase without or with alum adjuvants induced a clear anti-rasburicase antibody response, but intravenous (i.v.) injection did not. The lack of response to i.v. rasburicase was apparently due to active immune suppression since i.v.-treated mice showed blunted antibody and reduced T cell responses to subsequent i.p. injections of rasburicase. This blunted response was associated with a decrease in rasburicase-specific B cell and T cell responses and an increase in proportion of CD4+ FoxP3+ regulatory T cells (Treg) in the spleen. We examined the number of lymphocytes in peripheral blood after rasburicase i.v. injection. Rasburicase caused a transient reduction in B and T cells, but a robust and sustained depletion of rasburicase-specific B cells. Further experiments showed that rasburicase i.v. injection decreased the number of lymphocytes and was associated with apoptosis of both B cells and activated T cells and that the enhanced percentage of Treg cells was likely mediated by a macrophage-dependent pathway. Thus, our data suggest that apoptosis and depletion of antigen-specific B lymphocytes and upregulation of Treg cells may play important roles in the immune suppression induced by intravenous administration of a therapeutic protein.

Intravenous rasburicase-induced immune tolerance is associated with depletion of specific lymphocytes and up-regulation of regulatory T cells

Abstract Therapeutic proteins can be potent agents for treating serious diseases, but in many patients these proteins provoke antibody responses that blunt therapeutic efficacy. Intravenous administration of high doses of some proteins induces immune tolerance, but the mechanisms behind this effect are poorly understood. As a model to study tolerance induction in mice, we used Rasburicase, a commercial recombinant uricase used for treatment of hyperuricemia. Intraperitoneal (i.p.) injection of Rasburicase without or with alum provoked a clear anti-Rasburicase antibody response, but intravenous (i.v.) injection did not. The lack of response to i.v. Rasburicase was apparently due to active immune suppression, since i.v.-treated mice showed blunted antibody and reduced T cell responses to subsequent i.p. injections of Rasburicase. This blunted response was associated with a decrease in Rasburicase-specific B cells and T cell proliferation, and an increase in proportion of CD4+ FoxP3+ regulatory T cells (Treg). We examined the number of lymphocytes in peripheral blood after Rasburicase i.v. injection. Intravenous injection of rasburicase temporary reduced numbers of B cells and T cells, but robustly depleted Rasburicase-specific B cells in blood. Further results showed that rasburicase i.v. injection decreased the number of lymphocytes by inducing apoptosis of B cells and activated T cells. Thus, our data suggests that Rasburicase i.v. injection-induced apoptosis and depletion of lymphocytes and up-regulation of Treg cells play important roles in the intravenous therapeutic protein-induced immune tolerance.

Interferon-gamma and Interleukin-17 Modified Mesenchymal Stem Cells (MSC) Directly or Indirectly Modulate T Cell Responses By Expressing Inhibitory Factors, Downregulating T Cell Activation and Inducing Regulatory T Cells.

MSC have immunosuppressive properties beneficial for transplantation cellular therapy. We modified human bone marrow-derived MSC with inflammatory cytokines as a strategy to enhance MSC immunosuppression on T cells. MSC were preconditioned with inflammatory cytokines IFN-γ, TNF-α, IL-1β, IL-2, IL-12 and IL-17 for 5d and were co-cultured with T cells activated by the mitogen phytohemagglutinin (PHA). Modified MSC displayed greater immunosuppression on T cell proliferation compared to unmodified-MSC (UT:MSC). IL-6 gene expression significantly increased in TNF-α and IL-1β-modified MSC following 5d of preconditioning. MSCγ and TNF-α-modified MSC upregulated cyclooxygenase gene expression relative to UT:MSC while only IFN-γ induced indoleamine 2,3-dioxygenase expression in MSC. TGF-β1 gene expression was unaffected following cytokine modification of MSC and IL-10 was undetectable. Mechanistically, only IFN-γ modified MSC (MSCγ) increased the T cell negative co-stimulatory molecule B7-H1. Neutralization of B7-H1 failed to restore T cell proliferative responses suggesting a partial but non-exclusive role of B7-H1 in MSCγ immunosuppression. Furthermore, UT:MSC, MSCγ and IL-17 preconditioned MSC (MSC17) downregulated the T cell activation marker CD25 on CD4+ and CD8+ T cells to a similar extent but does not affect CD69 on T cells. Additionally, an increase in proportion of CD4+CD25hiCD127loFoxp3+ regulatory T cells (Tregs) was observed in PHA-activated T cells co-cultured with MSCγ (1.8 to 4.2-fold) and MSC17 (2.3 to 3-fold) relative to UT:MSC; an effect dependent on the MSC donor and responder T cells. In subsequent experiments, MSCγ and MSC17 that were co-cultured with PHA-activated CD4+CD25- T cells showed greater induction of Tregs (iTregs) compared to UT:MSC, with MSC17 showing highest iTregs up to 8.2-fold increase relative to UT:MSC. In 2 of 3 MSC donors, prostaglandin-2 protein levels were highest in MSC17 suggesting a possible involvement of prostaglandin-2 in MSC17-mediated Treg induction. In conclusion, proinflammatory cytokine preconditioning enhances immunosuppression in MSC.

Changes of CD4 ＋CD25highFoxp3 ＋regulatory T cells and their significance in childhood B-cell acute lymphocytic leukemia

Objective To investigate the changes of CD4 ＋CD25highFoxp3 ＋regulatory T （Treg） cells and their significance in immune escape of childhood B-cell acute lymphocytic leukemia （ B-ALL ） . Methods Forty-two children with B-ALL and twenty-eight age-matched healthy children were enrolled in this study.Flow cytometry analysis was performed to evaluate the proportion of CD 4 ＋CD25high Foxp3 ＋Treg cells as well as CD4 ＋CD25high ICOS＋Foxp3 ＋and CD4 ＋CD25high ICOS-Foxp3 ＋subsets in peripheral blood samples.The expression of associated molecules including IL-10, TGF-β, IL-35, TGF-βRII, ICOS and CD28 at protein level were also measured by flow cytometry analysis .The transcription level of Smad3/4, TIEG1 and Itch by CD4 ＋T cells were determined by quantitative real-time PCR.The concentration of TGF-βin plasma was detected by enzyme-linked immunosorbent assay.Results （1）The proportion of CD4 ＋CD25highFoxp3 ＋Treg cells in children with B-ALL were significantly higher than those of health subjects （P〈0.05）.The proportion of both ICOS ＋Foxp3 ＋and ICOS -Foxp3 ＋subsets were increased in comparison with those of control group （P〈0.05）, while the ratio of ICOS ＋Foxp3 ＋to ICOS-Foxp3 ＋was decreased （0.73 ±0.21 vs 1.87 ±0.59, P〈0.05）.（2） The expression of Foxp3, TGF-β, IL-10 and IL-35 by ICOS＋Foxp3 ＋Treg cells and the expression of membrane bound TGF-βby ICOS -Foxp3 ＋Treg cells were significantly increased in children with B-ALL （P〈0.05）.However, the expression of Foxp3 by ICOS -Foxp3 ＋Treg cells showed no significant difference between the two groups （P〉0.05）.（3）The concentra-tion of TGF-βin plasma from children with B-ALL were higher than those from control group [ （ 25 .83 ±12.65） ng/ml vs （8.59 ±5.73） ng/ml, P〈0.05].The expression of TGF-βRII and its associated mole-cules （Smad3/4, TIEG1 and Itch） by CD4 ＋T cells were significantly up-regulated.Moreover, an increased expression of ICOS and CD28 by CD4 ＋CD25highFoxp3 ＋Treg cells were also observed in children with B-ALL （P〈0.05）.Conclusion The hyper-activity of TGF-β, ICOS and CD28 signaling might be closely associ-ated with the increased proportion of CD4 ＋CD25high Foxp3 ＋Treg cells and the imbalance of its subsets in children with B-ALL. Key words: B-cell acute lymphoblastic leukemia; Regulatory T cells; Foxp3; ICOS; CD28

2,3,7,8-Tetrachlorodibenzo-p-dioxin Enhances Negative Selection of T Cells in the Thymus but Allows Autoreactive T Cells to Escape Deletion and Migrate to the Periphery

Exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), an environmental pollutant, has been shown to cause thymic atrophy and apoptosis. However, whether TCDD alters the process of T-cell selection in the thymus is not clear. To this end, we investigated the effects of TCDD in the context of the HY-T-cell receptor (TCR) transgenic (Tg) mouse model. We noted that negatively selecting male HY-TCR Tg mice were significantly more sensitive to the thymotoxic effects of TCDD relative to positively selecting female HY-TCR Tg mice, including increased reduction in cellularity and increased induction of apoptosis. TCDD exposure also altered the thymocyte subset composition in HY-TCR Tg male but not female mice. In addition, TCDD treatment resulted in increased extracellularly regulated kinase phosphorylation and lymphocyte-specific protein tyrosine kinase expression in thymocytes of HY-TCR Tg male but not female mice. The increase in proportion of CD8+ mature thymocytes noted in HY-TCR Tg male mice was reflected in the periphery, with TCDD-exposed HY-TCR Tg male mice having increased numbers of CD8+ T cells. Finally, we noted that the proliferative response of HY-TCR Tg male T cells to HY(self)-Ag was enhanced after exposure to TCDD, whereas that of HY-TCR Tg female mice was decreased. Taken together, these data suggest that TCDD alters the process of thymic selection, possibly by enhancing negative thymocyte selection, whereas at the same time allowing autoreactive T cells to escape deletion in the thymus and immigrate to the periphery.