Interleukin-7 Differentially Regulates The Activation, Proliferation, And Homing Of T-cells: Implications For Immunotherapy

Interleukin-7 (IL-7) is an essential lymphocyte growth factor required for the survival and proliferation of mature T-cells. As a therapeutic agent, IL-7 has the potential to restore T-cell numbers following immune depletion and to promote immunity against cancers. While the survival function of IL-7 is well established, less is known about how it supports T-cell expansion, a critical feature of the immune response. To study the biological effects of IL-7 on T-cell growth, we developed an in vitro culture technique to expand T-cells ex vivo. A significant finding from our studies is that IL-7 did not induce the expansion of all T-cells, indicating that there are inherent differences in the response of individual T-cell subsets to IL-7. Culture with high doses of IL-7 ( \u3e 150 ng/ml) preferentially expanded CD8 T-cells, but lead to the dramatic loss of CD4 T-cells which favored growth in lower dosages of IL-7 ( \u3e 10 ng/ml). This effect was due to the regulation of LCK, a kinase predominantly associated with the CD4 co-receptor. We found that transgenic expression of the CD4 co-receptor onto CD8 T-cells promoted their growth in lower concentrations of IL-7. Conversely, inhibition of LCK activity in CD4 T-cells restored their responsiveness to high doses of IL-7 as indicated by the activation of the transcription factor STAT5, in a manner similar to CD8 T-cells. Interestingly, not all CD8 T-cells expanded in high doses of IL-7 and this effect was specific to CD8 T-cells that expressed an activated memory phenotype. We found that IL-7 promoted the proliferation of CD8 T-cells through Cdc25A, a phosphatase required for cell cycle progression. Expression of a constitutively active Cdc25A could maintain T-cell survival and proliferation in the absence of IL-7, demonstrating that Cdc25A is a crucial transducer of IL-7 growth signals. Inhibition of Cdc25A was sufficient to decrease proliferation and down-regulate the expression of activation/ memory markers on CD8 T-cells in the presence of IL-7. Upon further study, we identified a novel role for IL-7 through Cdc25A in the regulation of CD62L, an adhesion molecule required for lymph node entry. Culture with high doses of IL-7 down-regulated the expression of CD62L, suggesting that high doses of IL-7 could affect the ability of T-cells to enter or re-enter the lymph nodes. Collectively, our findings demonstrate that IL-7 administration at the supraphysiological doses currently used in the clinical trials could have a negative impact on the growth of CD4 T-cells and the homing of CD8 T-cells to the lymph nodes, effects which can impede the generation of an effective immune response

Cytokine-driven cell cycling is mediated through Cdc25A

Lymphocytes are the central mediators of the immune response, requiring cytokines for survival and proliferation. Survival signaling targets the Bcl-2 family of apoptotic mediators, however, the pathway for the cytokine-driven proliferation of lymphocytes is poorly understood. Here we show that cytokine-induced cell cycle progression is not solely dependent on the synthesis of cyclin-dependent kinases (Cdks) or cyclins. Rather, we observe that in lymphocyte cell lines dependent on interleukin-3 or interleukin-7, or primary lymphocytes dependent on interleukin 7, the phosphatase Cdc25A is the critical mediator of proliferation. Withdrawal of IL-7 or IL-3 from dependent lymphocytes activates the stress kinase, p38 MAPK, which phosphorylates Cdc25A, inducing its degradation. As a result, Cdk/cyclin complexes remain phosphorylated and inactive and cells arrest before the induction of apoptosis. Inhibiting p38 MAPK or expressing a mutant Cdc25A, in which the two p38 MAPK target sites, S75 and S123, are altered, renders cells resistant to cytokine withdrawal, restoring the activity of Cdk/cyclin complexes and driving the cell cycle independent of a growth stimulus

JunD/AP-1-Mediated Gene Expression Promotes Lymphocyte Growth Dependent on Interleukin-7 Signal Transduction

Interleukin-7 (IL-7) is an essential cytokine for lymphocyte growth that has the potential for promoting immune reconstitution. This feature makes IL-7 an ideal candidate for therapeutic development. As with other cytokines, signaling through the IL-7 receptor induces the JAK/STAT pathway. However, the broad scope of IL-7 regulatory targets likely necessitates the use of other signaling components whose identities remain poorly defined. To this end, we used an IL-7 dependent T-cell line to examine how expression of the glycolytic enzyme, Hexokinase II (HXKII) was regulated by IL-7 in a STAT5-independent manner. Our studies revealed that IL-7 promoted the activity of JNK (Jun N-terminal Kinase), and that JNK, in turn, drove the expression of JunD, a component of the Activating Protein 1 (AP-1) transcription factors. Gel shifts showed that the AP-1 complex induced by IL-7 contained JunD but not c-Fos or c-Jun. Inhibition of JNK/JunD blocked glucose uptake and HXKII gene expression, indicating that this pathway was responsible for promoting HXKII expression. Because others had shown that JunD was a negative regulator of cell growth, we performed a bioinformatics analysis to uncover possible JunD-regulated gene targets. Our search revealed that JunD could control the expression of proteins involved in signal transduction, cell survival and metabolism. One of these growth promoters was the oncogene, Pim-1. Pim-1 is an IL-7-induced protein that was inhibited when the activities of JNK or JunD were blocked, showing that in IL-7 dependent T-cells JunD can promote positive signals transduced through Pim-1. This was confirmed when the IL-7-induced proliferation of CD8 T-cells was impaired upon JunD inhibition. These results show that engagement of the IL-7 receptor drives a signal that is more complex than the JAK/STAT pathway, activating JNK and JunD to induce rapid growth stimulation through the expression of metabolic and signaling factors like HXKII and Pim-1

Cytokine-driven cell cycling is mediated through Cdc25A

Lymphocytes are the central mediators of the immune response, requiring cytokines for survival and proliferation. Survival signaling targets the Bcl-2 family of apoptotic mediators, however, the pathway for the cytokine-driven proliferation of lymphocytes is poorly understood. Here we show that cytokine-induced cell cycle progression is not solely dependent on the synthesis of cyclin-dependent kinases (Cdks) or cyclins. Rather, we observe that in lymphocyte cell lines dependent on interleukin-3 or interleukin-7, or primary lymphocytes dependent on interleukin 7, the phosphatase Cdc25A is the critical mediator of proliferation. Withdrawal of IL-7 or IL-3 from dependent lymphocytes activates the stress kinase, p38 MAPK, which phosphorylates Cdc25A, inducing its degradation. As a result, Cdk/cyclin complexes remain phosphorylated and inactive and cells arrest before the induction of apoptosis. Inhibiting p38 MAPK or expressing a mutant Cdc25A, in which the two p38 MAPK target sites, S75 and S123, are altered, renders cells resistant to cytokine withdrawal, restoring the activity of Cdk/cyclin complexes and driving the cell cycle independent of a growth stimulus

IL-2 receptor γ chain cytokines differentially regulate human CD8+CD127+ and CD8+CD127− T cell division and susceptibility to apoptosis

Expression of IL-7 receptor α (CD127) is associated with naive and memory (i.e. non-effector) CD8+ T cell phenotypes. Effector CD8+ T cells are predominantly CD127− and most die by apoptosis. Therefore, CD127 appears to be a marker for CD8+ T cell differentiation, yet its role in CD8+ T cell survival and memory development is unclear. To address this, we investigated the cell death and cell division of isolated CD8+CD127+ and CD8+CD127− T cells in response to common IL-2 receptor γ chain (γC) cytokines other than IL-7. We show here that (i) memory cells (CD127+CD45RA−) divide frequently in response to either IL-2, -4 or -15; (ii) IL-2 and -15 enhance cell division in effector–memory-like cells (CD127−CD45RA+) while IL-4 enhances the cell division of effector cells (CD127−CD45RA−); (iii) CD8+CD127+ T cells are more sensitive to the anti-apoptotic effects of IL-2 or IL-15 than CD8+CD127− T cells and (iv) CD8+CD127+ T cell produce more Bcl-2 in response to IL-2 or IL-15 compared with CD8+CD127− T cells. Therefore, CD8+CD127+ and CD8+CD127− T cells differ in their responsiveness to cell division and anti-apoptotic signals from IL-2, -4 and -15. This suggests a role for γC cytokines in the pathogenesis of diseases in which CD127 expression is altered on CD8+ T cells such as in progressive viral infections and cancer

Genome-wide haplotype-based association analysis of major depressive disorder in Generation Scotland and UK Biobank

Generation Scotland received core funding from the Chief Scientist Office of the Scottish Government Health Directorate CZD/16/6 and the Scottish Funding Council HR03006. Genotyping of the GS:SFHS samples was carried out by the Genetics Core Laboratory at the Wellcome Trust Clinical Research Facility, Edinburgh, Scotland and was funded by the Medical Research Council UK and the Wellcome Trust (Wellcome Trust Strategic Award “STratifying Resilience and Depression Longitudinally” (STRADL) Reference 104036/Z/14/Z. YZ acknowledges support from China Scholarship Council. IJD is supported by the Centre for Cognitive Ageing and Cognitive Epidemiology which is funded by the Medical Research Council and the Biotechnology and Biological Sciences Research Council (MR/K026992/1). AMMcI and T-KC acknowledges support from the Dr Mortimer and Theresa Sackler Foundation. We are grateful to all the families who took part, the general practitioners and the Scottish School of Primary Care for their help in recruiting them, and the whole Generation Scotland team, which includes interviewers, computer and laboratory technicians, clerical workers, research scientists, volunteers, managers, receptionists, healthcare assistants and nurses. Ethics approval for the study was given by the NHS Tayside committee on research ethics (reference 05/S1401/8)Peer reviewedPublisher PD

Ex Vivo Expansion of Memory CD8 T Cells From Lymph Nodes or Spleen Through in Vitro Culture With Interleukin-7

Interleukin-7 (IL-7) increases lymphocyte numbers, a critical feature of immune reconstitution, through mechanisms that are still poorly understood. Part of the problem is that IL-7 is produced in limited amounts by non-lymphoid cells, making in vivo studies of the cytokine\u27s activity a challenge. To overcome this, we developed an in vitro system by which lymphocytes from secondary immune organs could be cultured to produce IL-7 responsive cells. Using this method, we showed that CD8hiCD44hi T cells accumulate in culture with IL-7 from a population of lymph node or splenic cells. These results were validated when a similar lymphocyte subset was found in mice expressing a constitutively active form of STAT5b, a key transducer of IL-7 signals. Interestingly, IL-7-expanded cells also up regulated the activation marker, CD69. The IL-7-derived CD44hiCD69hi cells were not generated from naïve cells, but expanded from an existing population, since culture in IL-7 of naïve lymphocytes from OT-1/Rag1-/- mice did not produce CD44hiCD69hi cells. Using the in vitro culture system to study lymphocytes from mice deficient in the apoptotic protein, BIM, we were able to attribute the expansion of CD8hiCD44hiCD69hi T cells to the proliferative and not survival activity of IL-7. The in vitro culture system provides an important new methodology to examine the activities of this essential as well as immunotherapeutic cytokine

Interlinking Interleukin-7

The signaling processes that maintain the homeostatic proliferation of peripheral T-cells and result in their self-renewal largely remain to be elucidated. Much focus has been placed on the anti-apoptotic function of the cytokine, interleukin-7 (IL-7), during T-cell development. But a more critical role has been ascribed to IL-7 as a mediator of peripheral T-cell maintenance. The biological effects responsive to IL-7 signaling are transduced through only a few well-known pathways. In this review we will focus on the signals transduced by IL-7 and similar cytokines, examining how proliferative signals originate from cytokine receptors, are amplified and eventually alter gene expression. In this regard we will highlight the crosstalk between pathways that promote survival, drive cell cycle progression and most importantly provide the needed energy to sustain these critical cellular activities. Though this review showcases much of what has been learned about IL-7 proliferative signaling, it also reveals the significant gaps in our knowledge about cytokine signaling in the very relevant context of peripheral T-cell homeostasis. © 2007 Elsevier Ltd. All rights reserved