Cyclosporin A effects during primary and secondary activation of human umbilical cord blood T lymphocytes

Coupled feedback regulation of nuclear factor of activated T-cells (NFAT) modulates activation-induced cell death of T cells

A properly functioning immune system is vital for an organism’s wellbeing. Immune tolerance is a critical feature of the immune system that allows immune cells to mount effective responses against exogenous pathogens such as viruses and bacteria, while preventing attack to self-tissues. Activation-induced cell death (AICD) in T lymphocytes, in which repeated stimulations of the T-cell receptor (TCR) lead to activation and then apoptosis of T cells, is a major mechanism for T cell homeostasis and helps maintain peripheral immune tolerance. Defects in AICD can lead to development of autoimmune diseases. Despite its importance, the regulatory mechanisms that underlie AICD remain poorly understood, particularly at an integrative network level. Here, we develop a dynamic multi-pathway model of the integrated TCR signalling network and perform model-based analysis to characterize the network-level properties of AICD. Model simulation and analysis show that amplified activation of the transcriptional factor NFAT in response to repeated TCR stimulations, a phenomenon central to AICD, is tightly modulated by a coupled positive-negative feedback mechanism. NFAT amplification is predominantly enabled by a positive feedback self-regulated by NFAT, while opposed by a NFAT-induced negative feedback via Carabin. Furthermore, model analysis predicts an optimal therapeutic window for drugs that help minimize proliferation while maximize AICD of T cells. Overall, our study provides a comprehensive mathematical model of TCR signalling and model-based analysis offers new network-level insights into the regulation of activation-induced cell death in T cells.

T Cells of Infants Are Mature, but Hyporeactive Due to Limited Ca2+ Influx

CD4 T cells in human infants and adults differ in the initiation and strength of their responses. The molecular basis for these differences is not yet understood. To address this the principle key molecular events of TCR- and CD28-induced signaling in naive CD4 T cells, such as Ca²⁺ influx, NFAT expression, phosphorylation and translocation into the nucleus, ERK activation and IL-2 response, were analyzed over at least the first 3 years of life. We report dramatically reduced IL-2 and TNFα responses in naive CD31⁺ T cells during infancy. Looking at the obligatory Ca²⁺ influx required to induce T cell activation and proliferation, we demonstrate characteristic patterns of impairment for each stage of infancy that are partly due to the differential usage of Ca²⁺ stores. Consistent with those findings, translocation of NFATc2 is limited, but still dependent on Ca²⁺ influx as demonstrated by sensitivity to cyclosporin A (CsA) treatment. Thus weak Ca²⁺ influx functions as a catalyst for the implementation of restricted IL-2 response in T cells during infancy. Our studies also define limited mobilization of Ca²⁺ ions as a characteristic property of T cells during infancy. This work adds to our understanding of infants’ poor T cell responsiveness against pathogens.

Umbilical cord blood T cells express multiple natural cytotoxicity receptors after IL-15 stimulation, but only NKp30 is functional

The natural cytotoxicity receptors (NCRs) NKp30, NKp44, and NKp46 are thought to be NK lineage restricted. Herein we show that IL-15 induces NCR expression on umbilical cord blood (UCB) T cells. NCRs were mainly on CD8(+) and CD56(+) UCB T cells. Only NKp30 was functional as demonstrated by degranulation, IFN-gamma release, redirected killing, and apoptosis. Since NCRs require adaptor proteins for function, the expressions of these adaptors were determined. The adaptors used by NKp30 and NKp46, FcepsilonR1gamma and CD3zeta, were detected in UCB T cells. There was a near absence of DAP12, the adaptor for NKp44, consistent with a hypofunctional state. NKp46 was on significantly fewer UCB T cells, possibly accounting for its lack of function. Adult peripheral blood (PB) T cells showed minimal NCR acquisition after culture with IL-15. Since UCB contains a high frequency of naive T cells, purified naive T cells from adult PB were tested. Although NKp30 was expressed on a small fraction of naive PB T cells, it was nonfunctional. In contrast to UCB, PB T cells lacked FcepsilonR1gamma expression. These results demonstrate differences between UCB and PB T cells regarding NCR expression and function. Such findings challenge the concept that NCRs are NK cell specific.

Umbilical cord blood T cells express multiple natural cytotoxicity receptors after IL-15 stimulation, but only NKp30 is functional

The natural cytotoxicity receptors (NCRs) NKp30, NKp44, and NKp46 are thought to be NK lineage restricted. Herein we show that IL-15 induces NCR expression on umbilical cord blood (UCB) T cells. NCRs were mainly on CD8(+) and CD56(+) UCB T cells. Only NKp30 was functional as demonstrated by degranulation, IFN-gamma release, redirected killing, and apoptosis. Since NCRs require adaptor proteins for function, the expressions of these adaptors were determined. The adaptors used by NKp30 and NKp46, FcepsilonR1gamma and CD3zeta, were detected in UCB T cells. There was a near absence of DAP12, the adaptor for NKp44, consistent with a hypofunctional state. NKp46 was on significantly fewer UCB T cells, possibly accounting for its lack of function. Adult peripheral blood (PB) T cells showed minimal NCR acquisition after culture with IL-15. Since UCB contains a high frequency of naive T cells, purified naive T cells from adult PB were tested. Although NKp30 was expressed on a small fraction of naive PB T cells, it was nonfunctional. In contrast to UCB, PB T cells lacked FcepsilonR1gamma expression. These results demonstrate differences between UCB and PB T cells regarding NCR expression and function. Such findings challenge the concept that NCRs are NK cell specific.

Effects of ciclosporin A, tacrolimus and sirolimus on cytokine production in neonatal immune cells

BACKGROUND

It was the aim of this study to evaluate the effects of the well-known immunosuppressive drugs ciclosporin A (CsA), tacrolimus and sirolimus on the intracytoplasmic cytokine expression of neonatal immune cells.

METHODS

Immunosuppressive drugs were added to whole blood cultures of neonatal cord blood samples (n = 17) and peripheral blood samples of adults (n = 17) in vitro prior to stimulation of lymphocytes with phorbol 12-myristate 13-acetate (PMA)/ionomycin or monocytes.

RESULTS

Upon exposure to ciclosporin A (500 ng/mL) or tacrolimus (25 ng/mL) the number of cytokine expressing T cells was almost completely blocked in neonatal T cells while sirolimus (10 ng/mL) only inhibited intracytoplasmatic tumour necrosis factor alpha (TNF-alpha) expression (mean% positive cells; 4.0 +/- 2.1% vs. 1.09 +/- 0.6%, p = 0.003), but mildly stimulated the intracellular expression of interleukin (IL)-2 (24.4 +/- 6.5% vs. 28.1 +/- 7.1%, p = 0.041). In cord blood lymphocytes, the inhibitory effect of ciclosporin A and tacrolimus was dose-dependent (e.g. IL-2: control, 12.3 +/- 5.33%, ciclosporin A 5 ng/mL, 10.1 +/- 5.5%; 50 ng/mL, 7.1 +/- 4.7%; 500 ng/mL, 1.2 +/- 0.3%; tacrolimus 0.25 ng/mL, 9.3 +/- 4.9%; 2.5 ng/mL, 6.1 +/- 3.3%; 25 ng/mL, 1.0 +/- 0.6%), while the function of adult lymphocytes was only impaired at high doses of both compounds. In contrast, the number of cytokine expressing monocytes was not influenced by ciclosporin A and tacrolimus except for a minor decrease of TNF-alpha producing neonatal monocytes after addition of tacrolimus (17.9% vs. 13.9%, p = 0.031). Interestingly, sirolimus was shown to inhibit intracellular IL-6 production in adults (63.1 +/- 12.7% vs. 52.0 +/- 16.0%, p = 0.005), but in neonatal monocytes intracellular IL-6 expression was stimulated (53.5 +/- 22.0% vs. 64.7 +/- 19.1%, p = 0.041).

CONCLUSIONS

The potent dose-dependent inhibitory effect of ciclosporin A and tacrolimus in cord blood lymphocytes provides the basis for further studies on functional immaturity of the neonatal immune system and for future strategies to optimize umbilical cord blood transplantion. Sirolimus was demonstrated to have a distinct effect on neonatal immune cells as shown by increased expression of IL-2 in lymphocytes and IL-6 in monocytes, while only lymphocytic TNF-alpha expression was inhibited.

Cytokine profiles of cord and adult blood leukocytes: differences in expression are due to differences in expression and activation of transcription factors

BACKGROUND

Stem cell transplantation as therapy for hematological disorders is often hampered by severe graft-versus-host-disease. This may be reduced by umbilical cord blood transplantation, an effect that has been attributed to qualitative differences between neonatal and adult T cells. We compared levels of secreted proteins and cytokine mRNA induced in cord blood leukocytes (CBL) and adult blood leukocytes (ABL) by various stimuli.

RESULTS

While interleukin-2 (IL-2) levels were similar in CBL and ABL, there was less induction of the Th1 cytokine interferon-gamma in CBL. Production of the Th2 cytokines IL-4, IL-5, and IL-13 and the hematopoietic cytokine IL-3 was much lower in CBL versus ABL after T-cell receptor-mediated stimulation, whereas production of GM-CSF was comparable in the 2 cell types. The lower levels of Th1 and Th2 cytokines were maintained in CBL during a 4-day time-course study, while after 12 hours IL-3 and GM-CSF reached in CBL levels similar to those in ABL. For all cytokines except IFN gamma, the IC50 values for inhibition by cyclosporin A were similar in ABL and CBL. In contrast, there was less expression and activation of transcription factors in CBL. Activation of NF-kappaB by TPA/ionomycin was detected in ABL but not CBL. Furthermore, there was less expression of the Th subset-specific transcription factors T-bet and c-maf in CBL versus ABL, whereas GATA-3 expression was similar. Expression of T-bet and c-maf correlated with expression of the Th1 and Th2 cytokines, respectively. Time course experiments revealed that T-bet expression was stimulated in both cell types, whereas c-maf and GATA-3 were induced only in ABL.

CONCLUSION

The diminished capability of CBL to synthesize cytokines is probably due to decreased activation of NF-kappaB, whereas differences in Th subsets are due to differences in regulation of Th lineage-specific transcriptions factors. We propose that the reduced incidence and severity of GvHD after allogeneic transplantation of umbilical CB cells is due to lesser activation of specific transcription factors and a subsequent reduction in production of certain cytokines.

Differential cyclosporin-A sensitivity on survival and activation of umbilical cord and adult peripheral blood CD4+ T cells

Enhanced cyclosporine-A (CsA) sensitivity of umbilical cord blood (CB) CD4(+) T cells may contribute to the lower incidence of graft-versus-host disease (GVHD) after mismatched CB transplantation. Interleukin (IL)-15, an IL-2 like gamma-chain signaling cytokine, may bypass CsA inhibition and play an important role in GVHD pathogenesis. The present study examines CsA sensitivity of IL-15-driven CB CD4(+) T cell survival, activation and proliferation, comparing adult peripheral blood (APB) CD4(+) T cell responses. We establish that (1) resting CB CD4(+) T cells were more susceptible to CsA-induced cell death than their adult counterpart; (2) IL-15 help support the survival of resting CB CD4(+) T cell under the influence of CsA, though to a lesser degree that observed in adults; (3) higher CsA sensitivity of CD25 up-regulation following TCR activation was observed in CB but more readily counteracted by IL-15 compared to adults; (4) IL-15-driven proliferation of TCR-activated CD4(+) T cells was more susceptible to CsA inhibition than corresponding adults; and (5) TCR-activated CB CD4(+) T cells surviving high dose CsA (5 microg/ml) in IL-15-supplemented cultures expressed significantly lower percentages of CD45RO(-)/CD25(+) subsets compared to corresponding APB. Taken together, the differential CsA sensitivity and IL-15 response between CB and APB CD4(+) T cells may contribute to the lessened GVHD severity in the setting of CB transplantation.

Effect of interleukin-15 on alloreactivity in umbilical cord blood

Interleukin(IL)-15 is a promising immunotherapeutic agent for immune reconstitution following stem cell transplantation. To investigate whether IL-15 would aggravate graft-versus-host disease (GVHD) in the setting of unrelated umbilical cord blood (CB) transplantation, we examined the effect of IL-15 on activation marker expression, proliferation and cytokine production of CB in a one-way mixed lymphocyte culture (MLC) assay. We found that IL-15 differentially enhanced CD69 and CD25 expression on CB T cells following allo-stimulation. The maximum degree of allo-specific CB proliferation was achieved on Day 6. IL-15 down-regulated the CB alloreactive proliferative response on Days 4, 6, and 8, with preferentially enhanced autologous proliferation. Exogenous IL-15 further enhanced CB TNF-alpha and IL-10 production in both autologous and allogeneic MLC 6 days after allopriming. Thus, IL-15 was effective in enhancing activation marker expression and cytokine production during CB alloreactivity, but failed to enhance allospecific proliferation. Further studies would be needed to study the role of IL-15 on GVHD in the setting of CB transplantation.

Effect of FK506 on the interleukin 15-driven proliferation and apoptosis of anti-CD3-activated umbilical cord blood T cells

BACKGROUND

Increased susceptibility of umbilical cord blood (CB) T cells to FK506 immunosuppression may contribute to the lessened severity of graft-vs-host disease in CB transplantation.

OBJECTIVE

To investigate the FK506 sensitivity of interleukin 15 (IL-15)- and IL-2-driven proliferation and apoptosis of anti-CD3-stimulated CB T cells compared with adult peripheral blood (APB) T cells.

METHODS

Surface flow cytometric analysis (CD25 and CD95), carboxyfluorescein diacetae succinimidyl ester staining to track CD3+ T-cell division, and flow cytometric analysis of apoptotic cell death using Annexin V were performed to determine the effect of FK506 on CD3+ T-cell activation and apoptosis after anti-CD3 stimulation in the presence of IL-15 or IL-2.

RESULTS

IL-15 is superior to IL-2 in promoting CD25 expression and proliferation of anti-CD3-stimulated CB and APB T cells. Although IL-15-driven proliferation evaluated by carboxyfluorescein diacetae succinimidyl ester staining revealed comparable sensitivity to FK506 in anti-CD3-stimulated CB and APB T cells, IL-15-driven CD25 up-regulation in CB T cells was more sensitive to FK506 inhibition than APB T cells. FK506 down-regulated anti-CD3-induced apoptosis in CB and APB T cells (P < .01). However, the FK506 sensitivity of anti-CD3-induced T-cell apoptosis was lost in IL-15-supplemented CB cultures (P = .51) but not in corresponding APB cultures (P = .002). The IL-15-enhanced Fas expression on CB T cells (CD95) was decreased by FK506, similar to that observed with adults.

CONCLUSIONS

We observed differential FK506 sensitivity of IL-15-driven CD25 up-regulation and apoptotic response comparing CB and APB T cells. This finding suggests the potential therapeutic benefit of FK506 in ameliorating graft-vs-host disease by decreasing IL-15-driven donor T-cell proliferation without inhibiting associated activation-induced apoptosis during CB transplantation.

Recipient-Specific Tolerance after HLA-Mismatched Umbilical Cord Blood Stem Cell Transplantation

BACKGROUND

Lower incidence and severity of acute graft versus host disease (GVHD) has been observed in leukemia patients receiving HLA-mismatched umbilical cord (UCB) transplants. However, despite the increased use of UCB in stem cell transplantation, the mechanisms underlying these favorable outcomes are not well delineated.

METHODS

We analyzed antigen specific lymphocyte responses after transplant to determine whether the decreased allogeneic responsiveness of UCB lymphocytes is attributable to pan-unresponsiveness, lymphocyte repressive or recipient-specific tolerance.

RESULTS

Circulating lymphocytes collected early (3 months) after UCB transplant demonstrate a less naïve phenotype compared with that in the infused graft. Additionally, after transplant, circulating peripheral blood UCB-derived lymphocytes produced normal levels of interferon-gamma and proliferated normally when stimulated with mitogen or third party alloantigen. In contrast, when stimulated with recipient antigen, circulating lymphocytes emerging posttransplant did not proliferate nor produce interferon-gamma. Moreover, analysis of interleukin-4 production revealed a Th2 response to recipient antigens. These data indicate early induction of immune tolerance of naïve UCB graft lymphocytes with skewing of transplant recipient-specific immune response towards Th2 cytokine profile.

CONCLUSIONS

UCB graft lymphocyte immune naivety and observed early tolerance induction may contribute to the observed favorable GVHD incidence, despite infusion of HLA mismatch grafts in the unrelated allogeneic setting.

Human umbilical cord matrix stem cells: preliminary characterization and effect of transplantation in a rodent model of Parkinson's disease

The umbilical cord contains an inexhaustible, noncontroversial source of stem cells for therapy. In the U.S., stem cells found in the umbilical cord are routinely placed into bio-hazardous waste after birth. Here, stem cells derived from human umbilical cord Wharton's Jelly, called umbilical cord matrix stem (UCMS) cells, are characterized. UCMS cells have several properties that make them of interest as a source of cells for therapeutic use. For example, they 1) can be isolated in large numbers, 2) are negative for CD34 and CD45, 3) grow robustly and can be frozen/thawed, 4) can be clonally expanded, and 5) can easily be engineered to express exogenous proteins. UCMS cells have genetic and surface markers of mesenchymal stem cells (positive for CD10, CD13, CD29, CD44, and CD90 and negative for CD14, CD33, CD56, CD31, CD34, CD45, and HLA-DR) and appear to be stable in terms of their surface marker expression in early passage (passages 4-8). Unlike traditional mesenchymal stem cells derived from adult bone marrow stromal cells, small populations of UCMS cells express endoglin (SH2, CD105) and CD49e at passage 8. UCMS cells express growth factors and angiogenic factors, suggesting that they may be used to treat neurodegenerative disease. To test the therapeutic value of UCMS cells, undifferentiated human UCMS cells were transplanted into the brains of hemiparkinsonian rats that were not immune-suppressed. UCMS cells ameliorated apomorphine-induced rotations in the pilot test. UCMS cells transplanted into normal rats did not produce brain tumors, rotational behavior, or a frank host immune rejection response. In summary, the umbilical cord matrix appears to be a rich, noncontroversial, and inexhaustible source of primitive mesenchymal stem cells.

Cord blood transplantation in adult patients

Early clinical reports outlining outcomes for primarily pediatric patients undergoing UCB transplantation point to delayed time to hematopoietic recovery and favorable incidence and severity of GvHD. Recently, clinical reports in adult patients identified the feasibility of UCB transplantation for those patients lacking an available histocompatible-related or unrelated adult donor Intensive clinical and laboratory research is ongoing focused on strategies to foster UCB allogeneic donor engraftment thereby allowing wider application of this stem cell source for patients requiring allogeneic transplantation.

Effect of interleukin-15 on anti-CD3/anti-CD28 induced apoptosis of umbilical cord blood CD4+ T cells

OBJECTIVES

Interleukin-15 (IL-15) has potential therapeutic advantage for patients receiving umbilical cord blood (CB) transplantation. The present study aims to examine the ability of IL-15 to modulate the survival, maturation, and function of anti-CD3/anti-CD28 stimulated CB CD4+ T cells, in comparison with responses from adult peripheral blood (APB) CD4+ T cells.

METHODS

Enriched CB and APB CD4+ T cells were stimulated with anti-CD3 and anti-CD28 (anti-CD3/anti-CD28) in the presence or absence of IL-15 (10 ng/mL) for 5 d. The percentages of apoptotic cells were assessed by propidium iodide/annexin-V flow cytometric staining. T-cell activation was analyzed with the expression of surface markers (CD45RO/CD69/CD25). Interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) production in culture supernatant was determined by enzyme-linked immunosorbent assay.

RESULTS

CB CD4+ T cells had a higher survival and lower apoptotic response following anti-CD3/anti-CD28 stimulation, compared with APB CD4+ T cells. IL-15 enhanced apoptosis and promoted CD45RO conversion of anti-CD3/anti-CD28 activated CB CD4+ T cells, an effect not observed with APB CD4+ T cells. Although activated CB CD4+ T cells expressed comparable level of CD69/CD25 expression to adults, IFN-gamma production of activated CB CD4+ T cells was markedly deficient compared with that of corresponding APB CD4+ T cells. Exogenous IL-15 further enhanced the production of IFN-gamma, but not TNF-alpha, of activated CB CD4+ T cells.

CONCLUSIONS

IL-15 preferentially resulted in an activation-enhancing effect on CB CD4+ T cells, accompanied by increased apoptosis. Our finding may have therapeutic implications while designing IL-15 immunotherapy for patients receiving CB transplant.

Reduced expression of NFAT-associated genes in UCB versus adult CD4+ T lymphocytes during primary stimulation

The cellular and molecular mechanisms underlying the blunted allo-responsiveness of umbilical cord blood (UCB) T cells have not been fully elucidated. Protein expression of NFATc2 (nuclear factor of activated T cells c2), a critical transcription factor necessary for up-regulation of multiple cytokines known to amplify T-cell allogeneic responses, is reduced in UCB T cells. Affymetrix oligonucleotide microarrays were used to compare gene expression of primary purified CD4+ UCB T cells to adult peripheral blood CD4+ T cells (AB) at baseline, 6, and 16 hours of primary stimulation. NFAT-regulated genes exhibited lower expression in UCB CD4+ T cells including the following: granulocyte-macrophage colony-stimulating factor (GM-CSF), interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), interleukin 3 (IL-3), IL-4, IL-5, IL-13, IL-2 receptor alpha (IL-2Ralpha; CD25), CD40L, and macrophage inflammatory protein 1 alpha (MIP-1alpha). Transcription factors involved in the NFAT pathway including C/EBPbeta, JunB, and Fosl1 (Fra-1), as well as Th1- and Th2-related transcription factors STAT4 (signal transducers and activators of transcription 4), T-bet, and c-maf showed reduced expression in UCB compared with AB during primary stimulation. Reduced cytokine, chemokine, and receptor expression was also found in UCB. Gene array data were confirmed using RNase protection assays, flow cytometry, and quantitative multiplexed cytokine measurements. Reduced global expression of NFAT-associated genes, as well as cytokines and chemokines, in UCB CD4+ T cells may contribute to the decreased graft-versus-host disease (GVHD) observed after UCB transplantation.

Reduced CTLA-4 protein and messenger RNA expression in umbilical cord blood T lymphocytes

OBJECTIVE

A favorable incidence and severity of graft-vs-host disease is observed in patients transplanted with banked, unrelated, HLA-mismatched umbilical cord blood (UCB) grafts, while the incidence of malignant relapse remains low. CTLA-4 mediates negative T-cell signaling and may contribute to the development of allogeneic tolerance. In this study, we compared protein and mRNA expression of CTLA-4 in stimulated UCB and adult peripheral blood T cells.

MATERIALS AND METHODS

T cells were isolated from UCB and adult peripheral blood and stimulated with anti-CD3 and anti-CD28 monoclonal antibodies. Cells were immunostained and analyzed by flow cytometry for both surface and intracellular expression of CTLA-4 in the presence and absence of cyclosporin A, and kinetics of CTLA-4 expression compared. CTLA-4 mRNA expression was measured using quantitative real-time polymerase chain reaction. NFAT1 protein levels were measured by Western blot analysis.

RESULTS

These studies demonstrate reduced surface and intracellular expression of CTLA-4 in stimulated UCB T cells compared to adult controls. Furthermore, reduced CTLA-4 protein expression in UCB T cells was noted to be in part transcriptionally regulated, as CTLA-4 mRNA levels also were significantly lower. Reduced CLTA-4 expression by UCB T cells followed the kinetics of delayed and reduced expression of the transcription factor NFAT1 by UCB T lymphocytes during primary stimulation. Moreover, cyclosporin A, which is known to modulate NFAT activation, reduced CTLA-4 protein expression in adult and UCB T cells.

CONCLUSION

Reduced expression of the key regulatory proteins CTLA-4 and NFAT-1 may contribute to favorable UCB T lymphocyte allogeneic responses.