Interleukin 7 receptor engagement stimulates tyrosine phosphorylation, inositol phospholipid turnover, proliferation, and selective differentiation to the CD4 lineage by human fetal thymocytes

Potential implications of interleukin-7 in chronic wound healing

Methods of identifying chronic wounds that will heal in a timely, coordinated fashion and those that will not, together with novel therapeutic strategies, are vital for progression in the field of wound healing. Interleukin (IL)-7 has been associated with various biological and pathological processes. The present study explored the potential role of IL-7 in wound healing. IL-7 expression levels were examined in a clinical cohort of chronic wounds using reverse transcription-quantitative polymerase chain reaction and immunohistochemical staining analysis. The impact of recombinant human IL-7 (rhIL-7) on the growth and migrational rates of HaCaT keratinocyte cells was subsequently examined using in vitro growth and electric cell-substrate impedance sensing functional assays. The mRNA expression levels of IL-7 were increased in the healed chronic wound tissue samples, compared with non-healed chronic wound tissue samples, although the difference was not statistically significant. Similarly, immunohistochemical analysis revealed a greater staining intensity of IL-7 in the healed chronic wound tissue sections compared with the non-healed tissue sections. Treatment with rhIL-7 did not affect HaCaT cell growth rates, but was shown to enhance cell migration, an effect that could be further enhanced through the addition of inhibitors of neuronal Wiskott-Aldrich syndrome protein and protein kinase B. The data of the present study suggest that the expression levels of IL-7 may be increased in healing chronic wounds, and thus IL-7 may have a role in this process, potentially through its effects on the cellular migration of keratinocytes.

Administration of interleukin-7 increases CD4 T cells in idiopathic CD4 lymphocytopenia

Idiopathic CD4 lymphopenia (ICL) is a rare syndrome defined by low CD4 T-cell counts (<300/µL) without evidence of HIV infection or other known cause of immunodeficiency. ICL confers an increased risk of opportunistic infections and has no established treatment. Interleukin-7 (IL-7) is fundamental for thymopoiesis, T-cell homeostasis, and survival of mature T cells, which provides a rationale for its potential use as an immunotherapeutic agent for ICL. We performed an open-label phase 1/2A dose-escalation trial of 3 subcutaneous doses of recombinant human IL-7 (rhIL-7) per week in patients with ICL who were at risk of disease progression. The primary objectives of the study were to assess safety and the immunomodulatory effects of rhIL-7 in ICL patients. Injection site reactions were the most frequently reported adverse events. One patient experienced a hypersensitivity reaction and developed non-neutralizing anti-IL-7 antibodies. Patients with autoimmune diseases that required systemic therapy at screening were excluded from the study; however, 1 participant developed systemic lupus erythematosus while on study and was excluded from further rhIL-7 dosing. Quantitatively, rhIL-7 led to an increase in the number of circulating CD4 and CD8 T cells and tissue-resident CD3 T cells in the gut mucosa and bone marrow. Functionally, these T cells were capable of producing cytokines after mitogenic stimulation. rhIL-7 was well tolerated at biologically active doses and may represent a promising therapeutic intervention in ICL. This trial was registered at www.clinicaltrials.gov as #NCT00839436.

Rational design of an immunoconjugate for selective knock-down of leukemia-specific E2A-PBX1 fusion gene expression in human Pre-B leukemia

The t(1;19)(q23;p13) is one of the most common chromosomal translocations in acute lymphoblastic leukemia (ALL) and results in production of the transforming oncoprotein E2A-PBX1. Here we first report a novel, biomarker-guided biotherapy strategy for personalized treatment of t(1;19)(+) ALL. A supervised interrogation of the gene expression profiles of primary leukemic cells from a cohort of 207 children with high risk B-lineage ALL identified up-regulated CD19 gene expression as a biomarker for t(1;19)(+) ALL. A disulfide-linked immunoconjugate of a 5-amino-modified 24 mer phosphorothioate anti-sense E2A-PBX1 oligonucleotide (AON) with a mAb specific for a CD19 receptor (αCD19-AON) was prepared as a CD19-directed and leukemia-specific biotherapeutic agent against E2A-PBX1(+) B-lineage ALL. Treatment of E2A-PBX1(+) leukemia cells with low nanomolar concentrations of αCD19-AON resulted in selective depletion of E2A-PBX1 transcripts and caused apoptotic destruction and abrogation of clonogenic growth. Subcutaneously administered αCD19-AON at a total dose level of 93 nmol kg(-1) delivered over 14 days using a micro-osmotic pump more than doubled the leukemia-free survival time of SCID mice in a xenograft model of E2A-PBX1(+) human B-lineage ALL (82.0 ± 1.9 days vs. 37.0 ± 0.1 days, P < 0.0001). Both the AON moiety and the targeting CD19-specific mAb moiety were required for the in vitro as well as in vivo anti-leukemic activity of αCD19-AON. The observed in vitro and in vivo anti-leukemic potency of the αCD19-AON immunoconjugate provides the first preclinical proof-of-principle that t(1;19)(+) high risk B-lineage ALL can be treated with leukemia-specific biotherapeutic agents that knock-down E2A-PBX1 expression.

Accelerated thymocyte maturation in IL-12Rβ2-deficient mice contributes to increased susceptibility to autoimmune inflammatory demyelination

IL-12Rβ2(-/-) mice, which are unresponsive to IL-12, develop severe experimental autoimmune encephalomyelitis (EAE). The mechanisms for enhanced autoimmunity are incompletely understood. We report that in IL-12Rβ2(-/-) mice, thymocytes undergo markedly accelerated maturation. This occurs at the transition from a double positive (DP) to a single positive (SP) phenotype, resulting in higher numbers of CD4 and CD8 SP cells, and to a lesser extent at the transition from double negative (DN) to DP cells. Accelerated maturation is observed in mice injected with anti-CD3 to mimic pre-T-cell receptor stimulation, and also in mice immunized with myelin oligodendrocyte glycoprotein (MOG) peptide to induce EAE.

A validated assay to measure soluble IL-7 receptor shows minimal impact of IL-7 treatment

IL-7 is a crucial cytokine for T cell hematopoiesis and peripheral homeostasis which by signaling through its receptor alpha chain (CD127) is essential for inducing T cell proliferation and survival. Since the specific CD127 alpha chain is found in a soluble state (sCD127) and at a high level in plasma (ng/mL), it is important to develop a sensitive and reliable assay in order to investigate the potential role of this receptor in the regulation of IL-7 physiologic, physipathologic and therapeutic effects. We here report a fully validated method to measure sCD127 in human and simian plasma using a method based on ELISA MSD technology. We demonstrate that sCD127 is detectable at various levels in the plasma of healthy humans as well as in that of healthy Rhesus and Cynomolgus macaques (106.72, 205.26 and 366.95 ng/mL respectively). Moreover, as opposed to the sCD25/IL-2 tandem, we demonstrate that IL-7 treatment has no impact on sCD127 plasma concentration in patients infected by HIV.

Impairment of organ-specific T cell negative selection by diabetes susceptibility genes: genomic analysis by mRNA profiling

BACKGROUND

T cells in the thymus undergo opposing positive and negative selection processes so that the only T cells entering circulation are those bearing a T cell receptor (TCR) with a low affinity for self. The mechanism differentiating negative from positive selection is poorly understood, despite the fact that inherited defects in negative selection underlie organ-specific autoimmune disease in AIRE-deficient people and the non-obese diabetic (NOD) mouse strain

RESULTS

Here we use homogeneous populations of T cells undergoing either positive or negative selection in vivo together with genome-wide transcription profiling on microarrays to identify the gene expression differences underlying negative selection to an Aire-dependent organ-specific antigen, including the upregulation of a genomic cluster in the cytogenetic band 2F. Analysis of defective negative selection in the autoimmune-prone NOD strain demonstrates a global impairment in the induction of the negative selection response gene set, but little difference in positive selection response genes. Combining expression differences with genetic linkage data, we identify differentially expressed candidate genes, including Bim, Bnip3, Smox, Pdrg1, Id1, Pdcd1, Ly6c, Pdia3, Trim30 and Trim12.

CONCLUSION

The data provide a molecular map of the negative selection response in vivo and, by analysis of deviations from this pathway in the autoimmune susceptible NOD strain, suggest that susceptibility arises from small expression differences in genes acting at multiple points in the pathway between the TCR and cell death.

Interleukin-7 in T-cell acute lymphoblastic leukemia: an extrinsic factor supporting leukemogenesis?

The malignant transformation and expansion of tumor cells involve both cell-autonomous mechanisms and microenvironment signals that regulate viability, nutrient utilization, metabolic activity and cell growth. In T-cell acute lymphoblastic leukemia (T-ALL), the co-culture of leukemic cells with stroma or the addition of particular cytokines prevents ex vivo spontaneous apoptosis. Interleukin-7 (IL-7), a cytokine produced by thymic and bone marrow stroma, increases the viability and proliferation of T-ALL cells. IL-7 induces the activation of Jak/STAT, MEK/Erk and PI3K/Akt signaling pathways in T-ALL cells. PI3K/Akt is the dominant pathway that mediates the effects of IL-7 on T-ALL. PI3K signaling is required for the induction of Bcl-2, the down-regulation of p27(kip1) and cell cycle progression. PI3K signaling is also required for the expression of the glucose transporter Glut1, uptake of glucose, activation of the metabolic machinery, increase in cell size, and maintenance of mitochondrial integrity. These observations suggest that substrates of molecular pathways activated by microenvironmental factors represent attractive molecular targets for the regulation of the viability and proliferation of T-ALL cells and provide the means for the development of novel treatment strategies.

Activation of PI3K is indispensable for interleukin 7-mediated viability, proliferation, glucose use, and growth of T cell acute lymphoblastic leukemia cells

Interleukin (IL)-7 is essential for normal T cell development. Previously, we have shown that IL-7 increases viability and proliferation of T cell acute lymphoblastic leukemia (T-ALL) cells by up-regulating Bcl-2 and down-regulating the cyclin-dependent kinase inhibitor p27^kip1. Here, we examined the signaling pathways via which IL-7 mediates these effects. We investigated mitogen-activated protein kinase (MEK)–extracellular signal-regulated kinase (Erk) and phosphatidylinositol-3-kinase (PI3K)–Akt (protein kinase B) pathways, which have active roles in T cell expansion and have been implicated in tumorigenesis. IL-7 induced activation of the MEK–Erk pathway in T-ALL cells; however, inhibition of the MEK–Erk pathway by the use of the cell-permeable inhibitor PD98059, did not affect IL-7–mediated viability or cell cycle progression of leukemic cells. IL-7 induced PI3K-dependent phosphorylation of Akt and its downstream targets GSK-3, FOXO1, and FOXO3a. PI3K activation was mandatory for IL-7–mediated Bcl-2 up-regulation, p27^kip1 down-regulation, Rb hyperphosphorylation, and consequent viability and cell cycle progression of T-ALL cells. PI3K signaling was also required for cell size increase, up-regulation of CD71, expression of the glucose transporter Glut1, uptake of glucose, and maintenance of mitochondrial integrity. Our results implicate PI3K as a major effector of IL-7–induced viability, metabolic activation, growth and proliferation of T-ALL cells, and suggest that PI3K and its downstream effectors may represent molecular targets for therapeutic intervention in T-ALL.

Soluble factor-mediated differentiation of CD4+CD8+ thymocytes to single positives in vitro

Although the thymic microenvironment provides the necessary elements for T-cell differentiation, the precise role of individual components remains to be determined. In this paper, attempts were made to address the possibility that CD4 or CD8 single-positive (SP) thymocytes could be developed from immature CD4+CD8+ (double-positive; DP) thymocytes in a suspension culture in the presence of soluble factors. We observed that IL-4 and IFN-gamma weakly induced DP cells to differentiate to CD4 cells, but not to CD8. In contrast, IL-2 weakly induced differentiation to CD8. Interestingly, Con A sup strongly induced differentiation to CD8 SP from the purified DP thymocytes prepared from C57BL/6 or LCMV TCRtg mice. In particular, it was found that thymocyte culture with Con A sup generated CD69+DP cells, and the CD69+DP differentiated to CD8 SP under the suspension culture with soluble factors. Thus, Con A sup or combinations of IL-2, IL-4 and IL-7 strongly induced differentiation of CD69+DP to CD8 SP, whereas individual cytokines did not. These results suggest that soluble factors like cytokines play an important role in the generation of SP thymocytes in the absence of thymic stromal cells, at least from a distinctive subpopulation like CD69+DP thymocytes, and perhaps from those of broader range when in conjunction with TCR/MHC interaction.

Interleukin-7 receptor expression and activation in nonhaematopoietic neoplastic cell lines

The high-affinity human interleukin-7 (IL-7)R is a heterodimeric complex consisting of the IL-7Ralpha and common interleukin-2 receptor gamma (IL-2Rgamma(c)) chains. Activation of the IL-7R complex is associated with tyrosine and serine residue phosphorylation of a number of intracellular substrates leading to proliferation and induction of various cellular differentiation processes. In this study, we demonstrate, by S1 nuclease protection assay, immunoprecipitation and in vitro kinase assay that functional human (h) IL-7R is expressed in haematopoietic and nonhaematopoietic cell lines. The National Cancer Institute (NCI) tumour panel of 60 cell lines (NCI60) was screened for the expression of IL-7R mRNA by S1 nuclease protection assay, and IL-7R mRNA was detected in 9 of 12 leukemia, 3 of 7 lung, 4 of 6 CNS, 2 of 7 melanoma, 2 of 7 renal, 1 of 6 colon and 1 of 6 breast cancer cell lines. Immunoblot analysis of haematopoietic, lung cancer and brain tumour cell lines demonstrated expression of IL-7R, IL-2Rgamma(c) and p59 fyn, suggesting that the components of an IL-7R signalling network are present in nonhaematopoietic neoplastic cells. Immunoprecipitation of IL-7Ralpha followed by an in vitro kinase assay demonstrated functional receptor phosphorylation events in the lung cancer cells but not in the brain tumour cell lines. The expression of functional IL-7R on epithelial tumour cells may represent a potential target for receptor-directed therapy.

Inhibition of in vitro spontaneous apoptosis by IL-7 correlates with Bcl-2 up-regulation, cortical/mature immunophenotype, and better early cytoreduction of childhood T-cell acute lymphoblastic leukemia

In normal T-cell development, IL-7 plays a nonredundant role as an antiapoptic factor by regulating Bcl-2 expression in pro-T cells. In the current study, we addressed the roles of IL-7 and related cytokines as apoptosis-modulating factors in precursor T-cell acute lymphoblastic leukemia (T-ALL). To this end, leukemic blasts from pediatric patients with T-ALL were prospectively investigated as to their responsiveness to IL-7, IL-4, and IL-2 (in terms of modulation of spontaneous apoptosis, assessed by flow cytometry), cytokine receptor expression profiles, and expression levels of Bcl-2 and Bax proteins. IL-7, in contrast to IL-4 and IL-2, was highly efficient in apoptosis inhibition , and this effect correlated with the expression levels of IL-7R chain and with the up-regulation of Bcl-2 protein expression (P&lt; .0001). Subclassification of T-ALL samples (n = 130) according to their in vitro IL-7 responses revealed that IL-7 refractory samples were more frequently positive for CD34 (P&lt; .0001) and the myeloid-associated antigen CD33 (P= .01), whereas IL-7 responsiveness was associated with an expression of more mature differentiation-associated T-cell antigens (CD1a, surface CD3, CD4/8; P &lt; .05). Furthermore, the extent of apoptosis inhibition by IL-7 in vitro quantitatively correlated with early cytoreduction as determined by the prednisone peripheral blood response on day 8 and cytoreduction in the marrow on day 15 (n = 87;P &lt; .05). Multivariate analysis of the apoptosis-related parameters investigated, including spontaneous apoptosis, its inhibition by IL-7, and expression levels of Bcl-2 and Bax, showed that only IL-7 responsiveness has an independent impact on early cytoreduction (P &lt; .05), thus indicating a potential prognostic relevance of IL-7 sensitivity in T-ALL.

Inhibition of in vitro spontaneous apoptosis by IL-7 correlates with Bcl-2 up-regulation, cortical/mature immunophenotype, and better early cytoreduction of childhood T-cell acute lymphoblastic leukemia

In normal T-cell development, IL-7 plays a nonredundant role as an antiapoptic factor by regulating Bcl-2 expression in pro-T cells. In the current study, we addressed the roles of IL-7 and related cytokines as apoptosis-modulating factors in precursor T-cell acute lymphoblastic leukemia (T-ALL). To this end, leukemic blasts from pediatric patients with T-ALL were prospectively investigated as to their responsiveness to IL-7, IL-4, and IL-2 (in terms of modulation of spontaneous apoptosis, assessed by flow cytometry), cytokine receptor expression profiles, and expression levels of Bcl-2 and Bax proteins. IL-7, in contrast to IL-4 and IL-2, was highly efficient in apoptosis inhibition , and this effect correlated with the expression levels of IL-7R chain and with the up-regulation of Bcl-2 protein expression (P< .0001). Subclassification of T-ALL samples (n = 130) according to their in vitro IL-7 responses revealed that IL-7 refractory samples were more frequently positive for CD34 (P< .0001) and the myeloid-associated antigen CD33 (P= .01), whereas IL-7 responsiveness was associated with an expression of more mature differentiation-associated T-cell antigens (CD1a, surface CD3, CD4/8; P < .05). Furthermore, the extent of apoptosis inhibition by IL-7 in vitro quantitatively correlated with early cytoreduction as determined by the prednisone peripheral blood response on day 8 and cytoreduction in the marrow on day 15 (n = 87;P < .05). Multivariate analysis of the apoptosis-related parameters investigated, including spontaneous apoptosis, its inhibition by IL-7, and expression levels of Bcl-2 and Bax, showed that only IL-7 responsiveness has an independent impact on early cytoreduction (P < .05), thus indicating a potential prognostic relevance of IL-7 sensitivity in T-ALL.

Role of IL-12 in Intrathymic Negative Selection

Cytokines are central regulatory elements in peripheral lymphocyte differentiation, but their role in T cell ontogeny is poorly defined. In the present study, we evaluated the role of IL-12 in thymocyte selection more directly by determining its role in two models of in vivo negative selection. In initial studies we demonstrated that abundant intrathymic IL-12 synthesis occurs during OVA peptide-induced negative selection of thymocytes in neonatal OVA-TCR transgenic mice, and such synthesis is associated with increased IL-12R β2-chain expression as well as STAT4 intracellular signaling. In further studies, we showed that this form of negative selection was occurring at the αβTCRlowCD4lowCD8low stage and was prevented by the coadministration of anti-IL-12. In addition, the IL-12-dependent thymocyte depletion was occurring through an intrathymic apoptosis mechanism, also prevented by administration of anti-IL-12. Finally, we showed that IL-12 p40−/− mice displayed aberrant negative selection of double positive CD4+CD8+ thymocytes when injected with anti-CD3 mAb. These studies suggest that intact intrathymic IL-12 production is necessary for the negative selection of thymocytes occurring in relation to a high “self” Ag load, possible through its ability to induce the thymocyte maturation and cytokine production necessary for such selection.

Interleukin-7: physiological roles and mechanisms of action

Interleukin-7 (IL-7), a product of stromal cells, provides critical signals to lymphoid cells at early stages in their development. Two types of cellular responses to IL-7 have been identified in lymphoid progenitors: (1) a trophic effect and (2) an effect supporting V(D)J recombination. The IL-7 receptor is comprised of two chains, IL-7R alpha and gamma(c). Following receptor crosslinking, rapid activation of several classes of kinases occurs, including members of the Janus and Src families and PI3-kinase. A number of transcription factors are subsequently activated including STATs, c-myc, NFAT and AP-1. However, it remains to be determined which, if any, previously identified pathway leads to the trophic or V(D)J endpoints. The trophic response to IL-7 involves protecting lymphoid progenitors from a death process that resembles apoptosis. This protection is partly mediated by IL-7 induction of Bcl-2, however other IL-7-induced events are probably also involved in the trophic response. The V(D)J response to IL-7 is partly mediated through increased production of Rag proteins (which cleave the target locus) and partly by increasing the accessibility of a target locus to cleavage through chromatin remodeling.

Ontogeny of the fetal immune system: study on pregnancies with Rh-isoimmunization and nonimmune fetal hydrops

This study aims at observing and comparing the antigen expression of some fetal T- and B-lymphocyte subpopulations in Rh-isoimmunization, which determines anemic hypoxia in the fetus, and nonimmune fetal hydrops (NIFH) which, even if there are some etiological factors involved, causes hipoxic hypoxia in the fetus. Twelve fetuses were studied by way of 30 fetal blood samples obtained by ultrasound-guided cordocentesis between the 20th and 36th gestational week. Twenty-four blood samples in all where taken from the eight fetuses with Rh-isoimmunization. Six blood samples were obtained from the four fetuses with NIFH. The lymphocyte phenotypes studied by monoclonal antibodies and flow cytometry were the following: CD3, CD4, CD8, expression of T-lymphocyte subpopulations; BsIg, CD19, expression of B-lymphocyte subpopulations. We observed a near-normal maturation process in fetuses with Rh isoimmunization, whereas in fetuses with NIFH we observed inhibition and/or delayed expression of T-lymphocytes. An early and increased B-lymphocyte activation marked a cooperation between the two systems in the early gestational periods.

Unresponsiveness of CD4-8+/- thymocytes to lectin stimulation in LEC mutant rats

A mutant strain of rat, LEC, shows a novel arrest of T-cell maturation from CD4+8+ to CD4+8-, but not to CD4-8+ cells in the thymus. The responsible mutant locus is designated the thid, which was acted upon in a recessive manner of inheritance. We found that LEC rat thymocytes failed to respond to interleukin (IL)-1, IL-6 and IL-7 in the presence of the mitogenic lectins, Allo A or concanavalin A (Con A). The unresponsiveness appeared to be due to unresponsiveness to the lectin stimulation rather than because of cytokine stimulation. Normal rat CD4-8+/- (consisting of CD4-8+ and CD4-8- thymocytes), CD4+/-8- (consisting of CD4+8- and CD4-8- thymocytes), and CD4-8- thymocyte subsets normally responded to mitogenic stimulation, while CD4+8+ thymocytes did not. In contrast, all LEC rat CD4-8+/-, CD4+/-8-, CD4-8- and CD4-8+ thymocytes did not respond to the mitogenic stimulation, suggesting that the unresponsiveness of the CD4-8+/- thymocytes seems to be responsible for the unresponsiveness of whole thymocytes in LEC rats. LEC rat CD4-8+/- thymocytes normally expressed Con A receptor (R), lymphocyte function-associated antigen-1 (LFA-1), and CD45, which are thought to be important molecules for lectin stimulation. When backcross rats from (F344xLEC)F1xLEC were examined, the phenotype for the thid mutation correlated with the [3H]thymidine deoxyribose (TdR) incorporation level in response to Con A stimulation; thymocytes from backcross rats showing +/thid phenotype responded to Con A stimulation normally, whereas thymocytes from backcross rats showing thid/thid phenotype showed significantly lower responsiveness compared with +/thid rats. However, in WKAH.C-thid congenic rat thymocytes that carry the thid mutation, the responsiveness to mitogenic stimulation was comparable to that of normal rat thymocytes. These results suggest that a defect in responsiveness to mitogenic stimulation in LEC rat thymocytes is controlled by multiple genetic loci and the thid locus is one of the important loci for the development of this abnormal phenotype.

Interleukin 7 (IL-7) receptor-specific cell killing by DAB389 IL-7: a novel agent for the elimination of IL-7 receptor positive cells

Interleukin 7 (IL-7) induces the proliferation of B cell progenitors in long-term bone marrow cultures, promotes the growth of resting fetal and adult thymocytes, and costimulates mature human T cell proliferation. IL-7 also induces cell growth in hematologic malignancies such as acute lymphoblastic leukemia, chronic lymphocytic leukemia, acute myelogenous leukemia, and Sezary syndrome. We have constructed a recombinant fusion protein, DAB389 IL-7, composed of the catalytic and transmembrane domains of diphtheria toxin (DT), fused to IL-7. We demonstrate that DAB389 IL-7 is selectively cytotoxic for only those cells bearing the IL-7 receptor and that entry into target cells is mediated through the receptor. The nontoxic mutant, DA(E149S)B389 IL-7, was constructed and used to demonstrate that the catalytic domain of DT is responsible for the ADP ribosylation of elongation factor 2 that results in cytotoxicity. Finally, we demonstrate that DA(E149S)B389 IL-7 induces the growth of IL-7-dependent cells, verifying the bioactivity of the IL-7 binding domain of DAB389 IL-7. We propose that DAB389 IL-7 may be an important reagent in studying the IL-7--IL-7 receptor complex and may possess potential as a therapeutic agent against IL-7 receptor-bearing hematologic malignancies.

The serum factor from patients with ulcerative colitis that induces T cell proliferation in the mouse thymus is interleukin-7

The disturbance of immune regulatory T cells is related to the pathogenesis of ulcerative colitis. Here we demonstrated and characterized the serum factor from ulcerative colitis patients that induced proliferation of intrathymic T cells. The factor isolated from the patient sera by a combination of gel filtration and anion-exchange chromatography induced proliferation of CD4+CD8- intrathymic T cells in the organ-cultured embryonic mouse thymus. Purification and amino acid sequence analysis of the serum factor demonstrated that the N-terminal 12 sequence was homologous to that of interleukin-7. SDS-PAGE and Western blot confirmed that purified serum factor was interleukin-7. Enzyme immunoassay demonstrated that the serum interleukin-7 concentration was significantly increased in the patients. PCR and Southern blot hybridization demonstrated that interleukin-7 mRNA expression was increased in the thymus tissues from patients but decreased in the colonic mucosa. Since interleukin-7 is a crucial cytokine for proliferation and differentiation of T cells in the thymus, the present study indicates that interleukin-7 may contribute to the disturbance of immune regulatory T cells in ulcerative colitis.

Protein kinase C in IL-2 signal transduction

Interleukin-2 (IL-2), secreted principally by activated helper T-cells, plays a pivotal role in the generation and regulation of the immune response. The various biologic functions of IL-2 have been the focus of intensive study over the years and have been well worked out. By contrast, an understanding of the intracellular signals coupled to the IL-2 receptor and responsible for mediating IL-2 effects in T-cells is far less developed, and the role that protein kinase C (PKC) may play in the various cellular responses to IL-2 receptor activation is unclear. In this article we will discuss IL-2, its receptors, and IL-2 signal transduction in relation to the physiological roles PKC activation may play in IL-2-mediated activation of T-cells and other hematopoietic cells.

Interleukin-7 induces T cell proliferation in the absence of Erk/MAP kinase activity

Interleukin (IL)-7 and IL-2 are important lymphoproliferative cytokines which both use the gamma c chain as part of their respective receptors. To learn more of their signaling mechanisms a comparison was made of the patterns of intracellular tyrosine phosphorylated proteins induced by these cytokines in the murine T cell line, CT6. Several similarities were revealed in the tyrosine phosphorylated proteins induced. However, a notable subset of proteins of mainly < 60 kDa were only phosphorylated by IL-2. Characterization of the two most prominent bands of this subset, pp54 and pp42, revealed these to contain Shc and p42MAP/Erk kinase, respectively. Further studies confirmed that IL-7 was unable to induce the phosphorylation of either the p44MAP/Erk or p42MAP/Erk or activation of the kinases. Shc is involved in activation of p21ras, a key event in the signaling cascade, via p72raf and MEK, leading to MAP/Erk kinase (MAPK) activation. These data indicate that this pathway is not utilized by IL-7 and may not, therefore, be essential for cytokine-driven T cell proliferation. This possibility was supported by studies with the MEK inhibitor PD098059, which had no selective effect on CT6 proliferation induced by IL-2 as compared with IL-7, although the drug completely inhibited MAP/Erk phosphorylation induced by IL-2.

Interleukin-7. Biology and implications for dermatology

In recent years, it has become apparent that IL-7, originally characterized as a growth factor for pre-B lymphocytes, also has important implications for the skin. Keratinocytes have been shown to produce IL-7. which in turn can elicit a variety of biological responses on several cell types residing in the skin. IL-7 has been demonstrated to augment the cytolytic activity of cytotoxic T cells (CTL) and natural killer (NK) cells against various neoplastic targets including melanoma cells. Proliferation and long-term survival of murine dendritic epidermal T lymphocytes (DETC) in vitro is supported by IL-7. IL-7 also induces secretion of inflammatory cytokines by monocytes/macrophages and renders these cells to become tumoricidal against melanoma cells. Normal and malignant melanocytes respond to IL-7 with increased expression of intercellular adhesion molecule (ICAM-1). In addition, IL-7 has been shown to act as growth factor for Sezary cells, suggesting a role of keratinocyte-derived IL-7 in the pathogenesis of cutaneous T cell lymphoma. Because of the potent in vitro immunomodulatory effects of IL-7 which have been confirmed in mouse tumor models, IL-7 may become a valuable additional agent to immunotherapeutical regimens currently studied in patients with advanced melanoma. This review summarizes our present knowledge about the molecular and immunological properties of IL7 with emphasis on the effects of that cytokine within the cutaneous compartment and the potential clinical utility in dermatology.

Interleukin-7 can induce the activation of Jak 1, Jak 3 and STAT 5 proteins in murine T cells

The activation of Janus protein tyrosine kinases (Jak) and STAT (signal transducer and activator of transcription) proteins has recently been linked to the signal transduction mechanism of several cytokines. IL-7 was observed to induce a rapid and dose-dependent tyrosine phosphorylation of Jak 1 and Jak 3 and concomitantly, the tyrosine phosphorylation and DNA binding activity of multiple STAT proteins. The STAT proteins utilized by IL-7 were identical to those induced by IL-2 and could be identified as various STAT 5 isoforms. Moreover, the induction of both Jak 1 and 3, and STAT 5 activity strongly correlated with the growth-promoting effects of IL-7, suggesting that this signal transduction mechanism may play a key role in IL-7-induced proliferation.

Interleukin-7 activates p56lck and p59fyn, two tyrosine kinases associated with the p90 interleukin-7 receptor in primary human T cells

We have investigated signaling events associated with the cloned 90-kDa (p90) interleukin-7 receptor (IL-7R) to determine whether changes in the signaling pathways initiated by this molecule can explain the ability of T cells to proliferate to IL-7 following activation. Using in vitro kinase assays we find that the p90 IL-7R in both unstimulated and activated human T cells is physically associated with two molecules with intrinsic kinase activity. Western blotting analysis reveals these proteins to be the src kinase enzymes, p59fyn and p56lck. Binding of human recombinant IL-7 to the p90 IL-7R results in increased activity of both receptor-associated kinases in both resting and activated mature T cells. Thus, the signaling pathways initiated via the p90 IL-7R-associated src kinases are unlikely to be solely responsible for the proliferation of only activated T cells in response to IL-7. Additional signals, which may derive from other IL-7R-associated molecules such as the gamma c, are clearly required for IL-7-driven proliferation of activated primary T cells.

Gamma chain-associated cytokine receptors signal through distinct transducing factors

The IL-2, IL-4, and IL-7 signaling pathways have been shown to utilize shared components. The receptors for these cytokines are composed of ligand-specific binding chains that associate with a shared signaling subunit, the common gamma (gamma c) chain. In addition, IL-2, IL-4, and IL-7 induce activation of a common set of nonreceptor tyrosine kinases, Jak-1 and Jak-3. We have further investigated the signaling events induced by these cytokines and find that the gamma c-associated receptors activate distinct signal transducing factors (STFs). In addition, we show that a 94-kDa STAT-related protein (p94) is activated in response to IL-2 and IL-7, but not IL-4. These data indicate that IL-2, IL-4, and IL-7 activate distinct signaling molecules which might be differentially recruited to the receptor complex by the ligand-specific units of the IL-2, IL-4, and IL-7 receptors.

Differential effects of interleukin-2 and interleukin-7 on the induction of CD4 and CD8 expression by double-negative human thymocytes

Expression of cell surface CD4 (in the absence of CD3/T cell receptor) characterizes an early stage of intrathymic T cell development. Here, we investigated the appearance of CD4 and CD8 expression on highly purified CD4-8- double-negative human thymocytes in response to interleukin (IL)-7 and IL-2. While IL-7 preferentially promoted the appearance of CD4 single-positive and CD4+8+ double-positive thymocytes, IL-2 primarily induced CD8 single-positive thymocytes. A significant fraction of CD4 single-positive cells generated from double-negative thymocytes via IL-7 lacked cell surface CD3 expression. In contrast, the majority of CD8 single-positive cells generated from double-negative thymocytes via IL-2 coexpressed CD3. We conclude that IL-7 and IL-2 exert differential effects on the differentiation of early human T cell progenitors.

Reconstitution of a functional interleukin (IL)-7 receptor demonstrates that the IL-2 receptor gamma chain is required for IL-7 signal transduction

The interleukin (IL)-2 receptor gamma chain has recently been shown to be a component of the IL-7 and IL-4 receptors. Using a transient transfection assay and the trans-activation of reporter gene constructs which are under the control of cytokine-responsive promoter elements, we have studied signal transduction through the IL-7 receptor (IL-7R). The reporter gene expression was not stimulated by receptors that contained the cytoplasmic domain of the IL-7R, either as intact IL-7R or as part of a chimeric receptor. However, co-expression of the IL-7R with the IL-2 receptor gamma chain was able to stimulate gene activation. For maximal stimulation the intact cytoplasmic domains of each chain was required.

Gene transfer of the interleukin (IL)-2 receptor beta chain into an IL-7-dependent pre-B cell line permits IL-2-driven proliferation: tyrosine phosphorylation of Shc is induced by IL-2 but not IL-7

Expression of the interleukin (IL)-2 receptor beta chain in the IL-7-dependent pre-B cell line IxN/2B permitted growth in presence of either IL-2 or IL-7, allowing for a direct comparison of intracellular signaling events. Protein tyrosine phosphorylation was essential for IL-2 and IL-7-induced signal transduction since the tyrosine kinase inhibitor herbimycin A blocked proliferation in response to both factors. Western blot analysis of tyrosine-phosphorylated proteins revealed that both IL-2 and IL-7 stimulation led to enhanced phosphorylation of proteins of 170-, 145-, 115- and 99-kDa, as well as induction of phosphorylation of a 96-kDa protein. However, a 55- and a 155-kDa protein were only phosphorylated after IL-2 stimulation. The 55-kDa protein specifically phosphorylated by IL-2 could be identified as p52shc which has recently been shown to be critically involved in Ras activation. Shc tyrosine phosphorylation as a result of IL-2 stimulation was consistently found in CTLL-2 cells and human T lymphoblasts. Taken together our results indicate that the IL-2- and IL-7-stimulated intracellular pathways are partially different and that Shc is a target of IL-2-, but not IL-7-, stimulated tyrosine phosphorylation.

Interleukin-7 induces the association of phosphatidylinositol 3-kinase with the alpha chain of the interleukin-7 receptor

The recently characterized receptor for interleukin (IL)-7 (IL-7R) includes a unique alpha chain as well as a common gamma chain shared with the receptors for IL-2 and IL-4. Engagement of the IL-7R activates the intracellular enzyme phosphatidylinositol (PtdIns) 3-kinase but the mechanism of PtdIns 3-kinase activation and the molecular basis of its interaction with IL-7R are not known. Here we show that IL-7 causes the 85-kDa regulatory subunit of PtdIns 3-kinase (p85), and PtdIns 3-kinase activity, to associate with the IL-7R. This interaction can be ascribed to ligand-induced phosphorylation of a single Tyr residue in the receptor's unique alpha chain. Herbimycin A, a specific protein tyrosine kinase inhibitor, suppresses not only tyrosine phosphorylation of the IL-7R but also its association with p85. A phosphopeptide corresponding to the sequence surrounding Tyr449 in the cytoplasmic tail of the IL-7R alpha chain, but not its non-phosphorylated analogue or phosphopeptides coincident with the sequences surrounding other alpha chain Tyr residues, efficiently competes out p85 binding. Replacement of Tyr449 with Phe results in a loss of p85 binding. Finally, soluble forms of the src homology 2 domains of p85, which bind directly to phosphotyrosyl peptides, specifically inhibit the association of p85 with the IL-7R. Thus, PtdIns 3-kinase recruitment occurs through a single, phosphotyrosine dependent recognition motif surrounding Tyr449 in the IL-7R alpha chain. This motif corresponds to a canonical sequence for p85 binding, Tyr(P)-X-X-Met. Since the closely related IL-2R and IL-4R also activate PtdIns 3-kinase but are devoid of such canonical motifs, our results suggest that the mechanism by which IL-7R recruits and activates PtdIns 3-kinase differs fundamentally from that used by the other receptors. PtdIns 3-kinase may, therefore, play a unique and important role in the biological response to IL-7.

Differential modulation of human multinegative (CD3-4-8-) thymocyte proliferation by monoclonal antibodies to CD45RA or to CD45

Human multinegative (CD3-4-8-19-; MN) thymocytes proliferate optimally in response to anti-CD2 plus anti-CD28 mAb plus PMA or IL-7. The role of CD45 was assessed by the addition of mAb to a CD45 common determinant, or to CD45RA. MN thymocytes are unresponsive to anti-CD2 mAb. Co-stimulation with anti-CD45RA generated 1.6-5.7-fold enhancement of a proliferative response, with maximal enhancement by cross-linkage of CD45RA molecules. The response to anti-CD2/28 mAb was reproducibly enhanced only by immobilized anti-CD45RA. Cross-linking of CD45RA and CD28 through the use of heteroconjugates of mAb did not enhance the co-stimulation by CD45RA. The most marked enhancement by anti-CD45RA occurred in suboptimal activation conditions. In contrast, the response to anti-CD2 or anti-CD2/28 was inhibited by mAb to CD45 common determinants (anti-CD45) in the presence or absence of PMA or IL-7, with the most profound inhibition (6-8-fold) detected in optimal proliferative conditions. Cross-linking of CD45 and CD28 through heteroconjugates of mAb was required as soluble anti-CD45 or immobilized anti-CD45 were unable to mediate inhibition. This inhibitory effect of (anti-CD45 x 28) was specific to MN thymocytes as no inhibition was detectable when peripheral blood T cells were treated with anti-CD2/28 and the same heteroconjugate. The differential effects of anti-CD45 and anti-CD45RA may reflect either CD45 heterogeneity on MN thymocytes, or the physical modulation of a single CD45 molecules by interactions at different epitopes, and the avidity of the relevant CD45 mAb for thymocyte CD45 isoforms may play a role.(ABSTRACT TRUNCATED AT 250 WORDS)

The molecular basis of X-linked severe combined immunodeficiency: the role of the interleukin-2 receptor gamma chain as a common gamma chain, gamma c

X-linked severe combined immunodeficiency is characterized by severe and persistent infections from early life resulting from profound impairment of both cellular and humoral immune function. XSCID is characterized by an absence or diminished number of T cells and histologic evidence of hypoplastic and abnormal differention of the thymic epithelium. The discovery that this disease results from the mutations of the IL-2R gamma chain was surprising since IL-2-deficient mice and human SCID patients had milder phenotypes. This led to the speculation that IL-2R gamma would prove to be a common gamma chain, gamma c, which would play important roles in other cytokine receptors in addition to the IL-2 receptor. There is now compelling evidence to support a role in at least two other cytokine receptors, namely the IL-4 and IL-7 receptors. Thus, with inactivation of gamma c, multiple cytokine systems are simultaneously affected, resulting in the profoundly impaired phenotype of XSCID. It is possible and even likely that gamma c will be found to be a functional component of additional receptors as well. These findings have resulted in a significant improvement in our understanding of the pathophysiologic development of the defects in XSCID and also have important ramifications for prenatal and postnatal diagnosis, carrier female identification, and gene therapy for XSCID.

Interleukin-7 regulates c-myc expression in murine T cells and thymocytes: a role for tyrosine kinase(s) and calcium mobilization

Interleukin-7 (IL-7) was originally identified as a pre-B cell growth factor whose proliferating activity has been extended to numerous target cells including T lymphocytes. We investigated c-myc mRNA expression, an oncogene associated with proliferation, in the murine T cell line D10 G4.1 and freshly isolated thymocytes since both target cells proliferate in response to IL-7. We find that blockade of the tyrosine kinase pathway by genistein, a potent tyrosine kinase inhibitor, inhibits both IL-7-dependent D10 G4.1 cell proliferation and c-myc mRNA expression which appears to involve de novo mRNA synthesis and to be under the control of short-lived protein repressor(s). We have also examined possible signal transduction pathways which might regulate c-myc mRNA expression in the murine T cell line. IL-7 biological activity is not affected by stimulation of the protein kinase C pathway by phorbol esters. Thus, IL-7 regulates c-myc mRNA expression in a protein kinase C-independent manner and these data are strengthened by protein kinase C depletion which does not modify IL-7 c-myc mRNA responsiveness. In contrast and independent of protein kinase C activation, intracellular calcium mobilization by means of ionomycin reduces IL-7 induction of c-myc mRNA expression and may represent a physiological mechanism whereby IL-7 bioactivity is regulated. The activity of IL-7 on c-myc mRNA expression has been extended to freshly isolated thymocytes and we find a synergistic effect of IL-7 with concanavalin A. Taken together our results illuminate the molecular mechanism of IL-7 c-myc induction in the T lineage by ascribing a role for tyrosine kinase and increase in intracellular calcium in both IL-7 induced gene induction and cell proliferation.

Interleukin-2 receptor gamma chain: a functional component of the interleukin-7 receptor

The interleukin-2 receptor gamma chain (IL-2R gamma) is a necessary component of functional IL-2 receptors. IL-2R gamma mutations result in X-linked severe combined immunodeficiency (XSCID) in humans, a disease characterized by the presence of few or no T cells. In contrast, SCID patients with IL-2 deficiency and IL-2-deficient mice have normal numbers of T cells, suggesting that IL-2R gamma is part of more than one cytokine receptor. By using chemical cross-linking, IL-2R gamma was shown to be physically associated with the IL-7 receptor. The presence of IL-2R gamma augmented both IL-7 binding affinity and the efficiency of internalization of IL-7. These findings may help explain the defects of XSCID. Given its role in more than one cytokine receptor system, the common gamma chain (gamma c) is proposed as the designation for IL-2R gamma.

Cellular signalling mechanisms in B lymphocytes

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Interleukin 7 receptor functions by recruiting the tyrosine kinase p59fyn through a segment of its cytoplasmic tail

Engagement of the cell surface receptor for interleukin 7 (IL-7R) provokes protein tyrosine phosphorylation, although the receptor lacks a kinase catalytic domain in its cytoplasmic tail. The molecular basis of this response is not known. Here we report that the IL-7R functions by recruiting p59fyn, an intracellular tyrosine kinase of the src family. Treatment of pre-B cells with IL-7 causes an enhancement of the catalytic activity of p59fyn, but not of the related kinase p62yes. IL-7-dependent stimulation of the enzyme phosphatidylinositol 3-kinase, a tyrosine kinase substrate, provides further evidence suggestive of p59fyn activation. We demonstrate that p59fyn forms part of a protein complex with the IL-7R. A chimeric receptor comprising the CD8 extracellular domain and the IL-7R cytoplasmic tail (CD8/IL-7R) recruits tyrosine kinase activity in transfected myeloma cells, and p59fyn can be detected in association with it by immunoprecipitation and immunoblotting. Conversely, p59fyn immunoprecipitates contain the phosphorylated CD8/IL-7R. We have identified a segment of the IL-7R cytoplasmic tail which mediates p59fyn recruitment: a truncated CD8/IL-7R containing only this segment recruits tyrosine kinase activity, associates with p59fyn, and activates phosphatidylinositol 3-kinase. Interestingly, this segment contains no tyrosine residues, although it is the phosphotyrosine-binding src homology domains of p59fyn and phosphatidylinositol 3-kinase which mediate their association with many growth factor receptors. Thus our results suggest that an unusual interaction links IL-7R to these two important signaling pathways.

Critical cytoplasmic region of the interleukin 6 signal transducer gp130 is conserved in the cytokine receptor family

Interleukin 6 (IL-6) signal is transduced through gp130 that associates with a complex of IL-6 and IL-6 receptor. Truncations or amino acid substitutions offe introduced in the cytoplasmic region of human gp130, and the mutant cDNAs were transfected into murine interleukin 3-dependent cells to determine amino acid residues critical for generating the IL-6-mediated growth signal. In the 277-amino acid cytoplasmic region of gp130, a 61-amino acid region proximal to the transmembrane domain was sufficient for generating the growth signal. In this region, two short segments were significantly homologous with other cytokine-receptor family members. One segment is conserved in almost all members of the family, and the other is found especially in granulocyte colony-stimulating factor receptor, interleukin 2 receptor beta chain, erythropoietin receptor, KH97 (a granulocyte/macrophage colony-stimulating factor receptor-associated molecule), and interleukin 3 receptor. gp130 molecules with mutations in either of these two segments could not transduce growth signal. Loss of signal-transducing ability of gp130 with such a mutation coincided with disappearance of IL-6-induced tyrosine phosphorylation of gp130.