Life Sciences Research for Lifelong Health

Publications klaus-okkenhaug

Title / Authors / Details Open Access Download

Immunomodulation of Selective Naive T Cell Functions by p110δ Inactivation Improves the Outcome of Mismatched Cell Transplantation.
Doisne JM, Hüber CM, Okkenhaug K, Colucci F

Allogeneic hematopoietic stem cell transplantation (HSCT) can treat certain hematologic malignancies due to the graft versus leukemia (GvL) effect but is complicated by graft versus host disease (GvHD). Expression of the p110δ catalytic subunit of the phosphoinositide 3-kinase pathway is restricted to leukocytes, where it regulates proliferation, migration, and cytokine production. Here, in a mouse model of fully mismatched hematopoietic cell transplantation (HCT), we show that genetic inactivation of p110δ in T cells leads to milder GvHD, whereas GvL is preserved. Inactivation of p110δ in human lymphocytes reduced T cell allorecognition. We demonstrate that both allostimulation and granzyme B expression were dependent on p110δ in naive T cells, which are the main mediators of GvHD, whereas memory T cells were unaffected. Strikingly, p110δ is not mandatory for either naive or memory T cells to mediate GvL. Therefore, immunomodulation of selective naive T cell functions by p110δ inactivation improves the outcome of allogeneic HSCT.

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Cell reports, , 2211-1247, , 2015

PMID: 25660021

Open Access

PI3K Signaling in B Cell and T Cell Biology.
Okkenhaug K, Turner M, Gold MR

Frontiers in immunology, 5, 1664-3224, 557, 2014

PMID: 25404931

Open Access

Inactivation of PI(3)K p110δ breaks regulatory T-cell-mediated immune tolerance to cancer.
K Ali, DR Soond, R Piñeiro, T Hagemann, W Pearce, EL Lim, H Bouabe, CL Scudamore, T Hancox, H Maecker, L Friedman, M Turner, K Okkenhaug, B Vanhaesebroeck

Inhibitors against the p110δ isoform of phosphoinositide-3-OH kinase (PI(3)K) have shown remarkable therapeutic efficacy in some human leukaemias. As p110δ is primarily expressed in leukocytes, drugs against p110δ have not been considered for the treatment of solid tumours. Here we report that p110δ inactivation in mice protects against a broad range of cancers, including non-haematological solid tumours. We demonstrate that p110δ inactivation in regulatory T cells unleashes CD8(+) cytotoxic T cells and induces tumour regression. Thus, p110δ inhibitors can break tumour-induced immune tolerance and should be considered for wider use in oncology.

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Nature, 510, , 407-411, 2014

PMID: 24919154
DOI: 10.1038/nature13444

Open Access

Haematological cancer: Idelalisib-targeting PI3Kδ in patients with B-cell malignancies.
JA Burger and K Okkenhaug

Idelalisib, the first PI3Kδ inhibitor in clinical use, has excellent activity in patients with chronic lymphocytic leukaemia and indolent B-cell lymphomas, heralding a new era of targeted therapy for these types of cancer. Idelalisib intercepts critical communications between B cells and the microenvironment, including B-cell receptor signalling and chemokine networks.

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Nature Reviews Clinical Oncology, 11, , 184-186, 2014

PMID: 24642682
DOI: 10.1038/nrclinonc.2014.42

Open Access

IL-21 promotes CD4 T cell responses by phosphatidylinositol 3-kinase-dependent upregulation of CD86 on B cells.
Attridge K, Kenefeck R, Wardzinski L, Qureshi OS, Wang CJ, Manzotti C, Okkenhaug K, Walker LS

The cytokine IL-21 is a potent immune modulator with diverse mechanisms of action on multiple cell types. IL-21 is in clinical use to promote tumor rejection and is an emerging target for neutralization in the setting of autoimmunity. Despite its clinical potential, the biological actions of IL-21 are not yet fully understood and the full range of effects of this pleiotropic cytokine are still being uncovered. In this study, we identify a novel role for IL-21 as an inducer of the costimulatory ligand CD86 on B lymphocytes. CD86 provides critical signals through T cell-expressed CD28 that promote T cell activation in response to Ag engagement. Expression levels of CD86 are tightly regulated in vivo, being actively decreased by regulatory T cells and increased in response to pathogen-derived signals. In this study, we demonstrate that IL-21 can trigger potent and sustained CD86 upregulation through a STAT3 and PI3K-dependent mechanism. We show that elevated CD86 expression has functional consequences for the magnitude of CD4 T cell responses both in vitro and in vivo. These data pinpoint CD86 upregulation as an additional mechanism by which IL-21 can elicit immunomodulatory effects.

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Journal of immunology (Baltimore, Md. : 1950), 192, 1550-6606, 2195-201, 2014

PMID: 24470500

Open Access

Two Birds with One Stone: Dual p110δ and p110γ Inhibition.
K Okkenhaug

In this issue of Chemistry & Biology, Winkler and colleagues describe the discovery and preclinical development of IPI-145, a new inhibitor of the phosphoinositide 3-kinase (PI3K) isoforms p110δ and p110γ that have entered clinical trials.

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Chemistry & biology, 20, 11, 1309-10, 2013

PMID: 24267274
DOI: 10.1016/j.chembiol.2013.11.002

Open Access

Phosphoinositide 3-Kinase δ Gene Mutation Predisposes to Respiratory Infection and Airway Damage.
I Angulo, O Vadas, F Garçon, E Banham-Hall, V Plagnol, TR Leahy, H Baxendale, T Coulter, J Curtis, C Wu, K Blake-Palmer, O Perisic, D Smyth, M Maes, C Fiddler, J Juss, D Cilliers, G Markelj, A Chandra, G Farmer, A Kielkowska, J Clark, S Kracker, M Debré, C Picard, I Pellier, N Jabado, JA Morris, G Barcenas-Morales, A Fischer, L Stephens, P Hawkins, JC Barrett, M Abinun, M Clatworthy, A Durandy, R Doffinger, E Chilvers, AJ Cant, D Kumararatne, K Okkenhaug, RL Williams, A Condliffe, S Nejentsev

Genetic mutations cause primary immunodeficiencies (PIDs), which predispose to infections. Here we describe Activated PI3K-δ Syndrome (APDS), a PID associated with a dominant gain-of-function mutation in which lysine replaced glutamic acid at residue 1021 (E1021K) in the p110δ protein, the catalytic subunit of phosphoinositide 3-kinase δ (PI3Kδ), encoded by the PIK3CD gene. We found E1021K in 17 patients from seven unrelated families, but not among 3346 healthy subjects. APDS was characterized by recurrent respiratory infections, progressive airway damage, lymphopenia, increased circulating transitional B cells, increased immunoglobulin M and reduced immunoglobulin G2 levels in serum and impaired vaccine responses. The E1021K mutation enhanced membrane association and kinase activity of p110δ. Patient-derived lymphocytes had increased levels of phosphatidylinositol 3,4,5-trisphosphate and phosphorylated AKT protein and were prone to activation-induced cell death. Selective p110δ inhibitors IC87114 and GS-1101 reduced the activity of the mutant enzyme in vitro, which suggested a therapeutic approach for patients with APDS.

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Science (New York, N.Y.), , , , 2013

PMID: 24136356
DOI: 10.1126/science.1243292

Open Access

PI3K p110δ is expressed by gp38(-)CD31(+) and gp38(+)CD31(+) spleen stromal cells and regulates their CCL19, CCL21, and LTβR mRNA levels.
Zotes TM, Spada R, Mulens V, Pérez-Yagüe S, Sorzano CO, Okkenhaug K, Carrera AC, Barber DF

The role of p110δ PI3K in lymphoid cells has been studied extensively, showing its importance in immune cell differentiation, activation and development. Altered T cell localization in p110δ-deficient mouse spleen suggested a role for p110δ in non-hematopoietic stromal cells, which maintain hematopoietic cell segregation. We tested this hypothesis using p110δ(WT/WT) mouse bone marrow to reconstitute lethally irradiated p110δ(WT/WT) or p110δ(D910A/D910A) (which express catalytically inactive p110δ) recipients, and studied localization, number and percentage of hematopoietic cell subsets in spleen and lymph nodes, in homeostatic conditions and after antigen stimulation. These analyses showed diffuse T cell areas in p110δ(D910A/D910A) and in reconstituted p110δ(D910A/D910A) mice in homeostatic conditions. In these mice, spleen CD4(+) and CD8(+) T cell numbers did not increase in response to antigen, suggesting that a p110δ(D910A/D910A) stroma defect impedes correct T cell response. FACS analysis of spleen stromal cell populations showed a decrease in the percentage of gp38(-)CD31(+) cells in p110δ(D910A/D910A) mice. qRT-PCR studies detected p110δ mRNA expression in p110δ(WT/WT) spleen gp38(-)CD31(+) and gp38(+)CD31(+) subsets, which was reduced in p110δ(D910A/D910A) spleen. Lack of p110δ activity in these cell populations correlated with lower LTβR, CCL19 and CCL21 mRNA levels; these molecules participate in T cell localization to specific spleen areas. Our results could explain the lower T cell numbers and more diffuse T cell areas found in p110δ(D910A/D910A) mouse spleen, as well as the lower T cell expansion after antigen stimulation in p110δ(D910A/D910A) compared with p110δ(WT/WT) mice.

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PloS one, 8, 1932-6203, e72960, 2013

PMID: 24009720

Open Access

A protocol for construction of gene targeting vectors and generation of homologous recombinant embryonic stem cells.
H Bouabe, K Okkenhaug

The completion of human and mouse genome sequencing has confronted us with huge amount of data sequences that certainly need decades and many generations of scientists to be reasonably interpreted and assigned to physiological functions, and subsequently fruitfully translated into medical application. A means to assess the function of genes provides gene targeting in mouse embryonic stem cells (ESCs) that enables to introduce site-specific modifications in the mouse genome, and analyze their physiological consequences. Gene targeting enables almost any type of genetic modifications of interest, ranging from gene insertion (e.g., insertion of human-specific genes or reporter genes), gene disruption, point mutations, and short- and long-range deletions, inversions. Site-specific modification into the genome of ESCs can be reached by homologous recombination using targeting vectors. Here, we describe a protocol to generate targeting constructs and homologous recombinant ESCs.

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Methods in molecular biology (Clifton, N.J.), 1064, , 337-54, 2013

PMID: 23996269
DOI: 10.1007/978-1-62703-601-6_24

Open Access

Gene targeting in mice: a review.
H Bouabe, K Okkenhaug

The ability to introduce DNA sequences (e.g., genes) of interest into the germline genome has rendered the mouse a powerful and indispensable experimental model in fundamental and medical research. The DNA sequences can be integrated into the genome randomly or into a specific locus by homologous recombination, in order to: (1) delete or insert mutations into genes of interest to determine their function, (2) introduce human genes into the genome of mice to generate animal models enabling study of human-specific genes and diseases, e.g., mice susceptible to infections by human-specific pathogens of interest, (3) introduce individual genes or genomes of pathogens (such as viruses) in order to examine the contributions of such genes to the pathogenesis of the parent pathogens, (4) and last but not least introduce reporter genes that allow monitoring in vivo or ex vivo the expression of genes of interest. Furthermore, the use of recombination systems, such as Cre/loxP or FRT/FLP, enables conditional induction or suppression of gene expression of interest in a restricted period of mouse's lifetime, in a particular cell type, or in a specific tissue. In this review, we will give an updated summary of the gene targeting technology and discuss some important considerations in the design of gene-targeted mice.

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Methods in molecular biology (Clifton, N.J.), 1064, , 315-36, 2013

PMID: 23996268
DOI: 10.1007/978-1-62703-601-6_23

Open Access

Rules of engagement: distinct functions for the four class I PI3K catalytic isoforms in immunity.
K Okkenhaug

Mammalian cells can express up to four different class I phosphatidylinositide 3-kinase (PI3K) isoforms, each of which is engaged by tyrosine kinases or G protein-coupled receptors (GPCRs) to generate the second messenger signaling molecule PtdIns(3,4,5)P₃ (PIP₃). The p110α and p110β isoforms are relatively widely expressed, whereas p110γ and p110δ are more highly expressed in cells of the immune system than in other cell types. Nevertheless, each of the four class I PI3Ks have been shown to participate in the orchestration of the signaling events that lead to immune cell development and control of gene expression, skewing toward individual cell lineage subsets and proliferation.

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Annals of the New York Academy of Sciences, 1280, , 24-6, 2013

PMID: 23551098
DOI: 10.1111/nyas.12027

Open Access

Signaling by the phosphoinositide 3-kinase family in immune cells.
K Okkenhaug

Phosphoinositide 3-kinases (PI3Ks) control many important aspects of immune cell development, differentiation, and function. Mammals have eight PI3K catalytic subunits that are divided into three classes based on similarities in structure and function. Specific roles for the class I PI3Ks have been broadly investigated and are relatively well understood, as is the function of their corresponding phosphatases. More recently, specific roles for the class II and class III PI3Ks have emerged. Through vertebrate evolution and in parallel with the evolution of adaptive immunity, there has been a dramatic increase not only in the genes for PI3K subunits but also in genes for phosphatases that act on 3-phosphoinositides and in 3-phosphoinositide-binding proteins. Our understanding of the PI3Ks in immunity is guided by fundamental discoveries made in simpler model organisms as well as by appreciating new adaptations of this signaling module in mammals in general and in immune cells in particular.

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Annual review of immunology, 31, , 675-704, 2013

PMID: 23330955
DOI: 10.1146/annurev-immunol-032712-095946

Open Access

PDK1 regulation of mTOR and hypoxia-inducible factor 1 integrate metabolism and migration of CD8+ T cells.
Finlay DK, Rosenzweig E, Sinclair LV, Feijoo-Carnero C, Hukelmann JL, Rolf J, Panteleyev AA, Okkenhaug K, Cantrell DA

mTORC1 (mammalian target of rapamycin complex 1) controls transcriptional programs that determine CD8+ cytolytic T cell (CTL) fate. In some cell systems, mTORC1 couples phosphatidylinositol-3 kinase (PI3K) and Akt to the control of glucose uptake and glycolysis. However, PI3K-Akt-independent mechanisms control glucose metabolism in CD8+ T cells, and the role of mTORC1 has not been explored. The present study now demonstrates that mTORC1 activity in CD8+ T cells is not dependent on PI3K or Akt but is critical to sustain glucose uptake and glycolysis in CD8+ T cells. We also show that PI3K- and Akt-independent pathways mediated by mTORC1 regulate the expression of HIF1 (hypoxia-inducible factor 1) transcription factor complex. This mTORC1-HIF1 pathway is required to sustain glucose metabolism and glycolysis in effector CTLs and strikingly functions to couple mTORC1 to a diverse transcriptional program that controls expression of glucose transporters, multiple rate-limiting glycolytic enzymes, cytolytic effector molecules, and essential chemokine and adhesion receptors that regulate T cell trafficking. These data reveal a fundamental mechanism linking nutrient and oxygen sensing to transcriptional control of CD8+ T cell differentiation.

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The Journal of experimental medicine, 209, 1540-9538, 2441-53, 2012

PMID: 23183047

Open Access

The Therapeutic Potential for PI3K Inhibitors in Autoimmune Rheumatic Diseases.
E Banham-Hall, MR Clatworthy, K Okkenhaug

The class 1 PI3Ks are lipid kinases with key roles in cell surface receptor-triggered signal transduction pathways. Two isoforms of the catalytic subunits, p110γ and p110δ, are enriched in leucocytes in which they promote activation, cellular growth, proliferation, differentiation and survival through the generation of the second messenger PIP3. Genetic inactivation or pharmaceutical inhibition of these PI3K isoforms in mice result in impaired immune responses and reduced susceptibility to autoimmune and inflammatory conditions. We review the PI3K signal transduction pathways and the effects of inhibition of p110γ and/or p110δ on innate and adaptive immunity. Focusing on rheumatoid arthritis and systemic lupus erythematosus we discuss the preclinical evidence and prospects for small molecule inhibitors of p110γ and/or p110δ in autoimmune disease.

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The open rheumatology journal, 6, , 245-58, 2012

PMID: 23028409
DOI: 10.2174/1874312901206010245

Open Access

Blockade of phosphatidylinositol 3-kinase PI3Kδ or PI3Kγ reduces IL-17 and ameliorates imiquimod-induced psoriasis-like dermatitis.
A Roller, A Perino, P Dapavo, E Soro, K Okkenhaug, E Hirsch, H Ji

Psoriasis is a chronic inflammatory skin disease triggered by interplay between immune mediators from both innate and adaptive immune systems and skin tissue, in which the IL-23/IL-17 axis is critical. PI3Kδ and PI3Kγ play important roles in various immune cell functions. We found that mice lacking functional PI3Kδ or PI3Kγ are largely protected from imiquimod (IMQ)-induced psoriasis-like dermatitis, correlating with reduced IL-17 levels in the lesions, serum, and the draining lymph nodes. TCRγδ T cells were the major IL-17-producing population in the draining lymph nodes and were significantly diminished in IMQ-treated PI3Kδ knockin and PI3Kγ knockout mice. We also show that PI3Kδ and PI3Kγ inhibitors reduced IFN-γ production by human TCRγδ T cells and IL-17 and IFN-γ production by PBMCs from psoriatic or healthy donors. In addition, inhibition of PI3Kγ, but not PI3Kδ, blocked chemotaxis of CCR6(+)IL-17-producing cells from IMQ-treated mice or healthy human donors. Taken together, these data indicate that PI3Kδ and/or PI3Kγ inhibitors should be considered for treating IL-17-driven diseases, such as psoriasis.

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Journal of immunology (Baltimore, Md. : 1950), 189, 9, 4612-20, 2012

PMID: 23024273
DOI: 10.4049/jimmunol.1103173

Open Access

Does the PI3K pathway promote or antagonize regulatory T cell development and function?
DR Soond, EC Slack, OA Garden, DT Patton, K Okkenhaug

Regulatory T cells (Tregs) prevent autoimmunity and inflammation by suppressing the activation of other T cells and antigen presenting cells. The role of phosphoinositide 3-kinase (PI3K) signaling in Treg is controversial. Some studies suggest that inhibition of the PI3K pathway is essential for the development of Tregs whereas other studies have shown reduced Treg numbers and function when PI3K activity is suppressed. Here we attempt to reconcile the different studies that have explored PI3K and the downstream effectors Akt, Foxo, and mTOR in regulatory T cell development and function and discuss the implications for health and therapeutic intervention.

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Frontiers in immunology, 3, , 244, 2012

PMID: 22912633
DOI: 10.3389/fimmu.2012.00244

Open Access

Pten loss in CD4 T cells enhances their helper function but does not lead to autoimmunity or lymphoma.
DR Soond, F Garçon, DT Patton, J Rolf, M Turner, C Scudamore, OA Garden, K Okkenhaug

PTEN, one of the most commonly mutated or lost tumor suppressors in human cancers, antagonizes signaling by the PI3K pathway. Mice with thymocyte-specific deletion of Pten rapidly develop peripheral lymphomas and autoimmunity, which may be caused by failed negative selection of thymocytes or from dysregulation of postthymic T cells. We induced conditional deletion of Pten from CD4 Th cells using a Cre knocked into the Tnfrsf4 (OX40) locus to generate OX40(Cre)Pten(f) mice. Pten-deficient Th cells proliferated more and produced greater concentrations of cytokines. The OX40(Cre)Pten(f) mice had a general increase in the number of lymphocytes in the lymph nodes, but not in the spleen. When transferred into wild-type (WT) mice, Pten-deficient Th cells enhanced anti-Listeria responses and the clearance of tumors under conditions in which WT T cells had no effect. Moreover, inflammatory responses were exaggerated and resolved later in OX40(Cre)Pten(f) mice than in WT mice. However, in contrast with models of thymocyte-specific Pten deletion, lymphomas and autoimmunity were not observed, even in older OX40(Cre)Pten(f) mice. Hence loss of Pten enhances Th cell function without obvious deleterious effects.

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Journal of immunology (Baltimore, Md. : 1950), 188, 12, 5935-43, 2012

PMID: 22611241
DOI: 10.4049/jimmunol.1102116

Open Access

Genetic or pharmaceutical blockade of phosphoinositide 3-kinase p110δ prevents chronic rejection of heart allografts.
H Ying, H Fu, ML Rose, AM McCormack, P Sarathchandra, K Okkenhaug, FM Marelli-Berg

Chronic rejection is the major cause of long-term heart allograft failure, characterized by tissue infiltration by recipient T cells with indirect allospecificity. Phosphoinositol-3-kinase p110δ is a key mediator of T cell receptor signaling, regulating both T cell activation and migration of primed T cells to non-lymphoid antigen-rich tissue. We investigated the effect of genetic or pharmacologic inactivation of PI3K p110δ on the development of chronic allograft rejection in a murine model in which HY-mismatched male hearts were transplanted into female recipients. We show that suppression of p110δ activity significantly attenuates the development of chronic rejection of heart grafts in the absence of any additional immunosuppressive treatment by impairing the localization of antigen-specific T cells to the grafts, while not inducing specific T cell tolerance. p110δ pharmacologic inactivation is effective when initiated after transplantation. Targeting p110δ activity might be a viable strategy for the treatment of heart chronic rejection in humans.

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PloS one, 7, 3, e32892, 2012

PMID: 22479345
DOI: 10.1371/journal.pone.0032892

Open Access

PI3Kβ plays a critical role in neutrophil activation by immune complexes.
S Kulkarni, C Sitaru, Z Jakus, KE Anderson, G Damoulakis, K Davidson, M Hirose, J Juss, D Oxley, TA Chessa, F Ramadani, H Guillou, A Segonds-Pichon, A Fritsch, GE Jarvis, K Okkenhaug, R Ludwig, D Zillikens, A Mocsai, B Vanhaesebroeck, LR Stephens, PT Hawkins

Neutrophils are activated by immunoglobulin G (IgG)-containing immune complexes through receptors that recognize the Fc portion of IgG (FcγRs). Here, we used genetic and pharmacological approaches to define a selective role for the β isoform of phosphoinositide 3-kinase (PI3Kβ) in FcγR-dependent activation of mouse neutrophils by immune complexes of IgG and antigen immobilized on a plate surface. At low concentrations of immune complexes, loss of PI3Kβ alone substantially inhibited the production of reactive oxygen species (ROS) by neutrophils, whereas at higher doses, similar suppression of ROS production was achieved only by targeting both PI3Kβ and PI3Kδ, suggesting that this pathway displays stimulus strength-dependent redundancy. Activation of PI3Kβ by immune complexes involved cooperation between FcγRs and BLT1, the receptor for the endogenous proinflammatory lipid leukotriene B₄. Coincident activation by a tyrosine kinase-coupled receptor (FcγR) and a heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptor (BLT1) may provide a rationale for the preferential activation of the β isoform of PI3K. PI3Kβ-deficient mice were highly protected in an FcγR-dependent model of autoantibody-induced skin blistering and were partially protected in an FcγR-dependent model of inflammatory arthritis, whereas combined deficiency of PI3Kβ and PI3Kδ resulted in near-complete protection in the latter case. These results define PI3Kβ as a potential therapeutic target in inflammatory disease.

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Science signaling, 4, 168, ra23, 2011

PMID: 21487106
DOI: 10.1126/scisignal.2001617

Open Access

The PI3K p110δ regulates expression of CD38 on regulatory T cells.
DT Patton, MD Wilson, WC Rowan, DR Soond, K Okkenhaug

The PI3K pathway has emerged as a key regulator of regulatory T cell (Treg) development and homeostasis and is required for full Treg-mediated suppression. To identify new genes involved in PI3K-dependent suppression, we compared the transcriptome of WT and p110δ(D910A) Tregs. Among the genes that were differentially expressed was the gene for the transmembrane cyclic ADP ribose hydrolase CD38. Here we show that CD38 is expressed mainly by a subset of Foxp3(+)CD25(+)CD4(+) T cells originating in the thymus and on Tregs in the spleen. CD38(high) WT Tregs showed superior suppressive activity to CD38(low) Tregs, which failed to upregulate CD73, a surface protein which is important for suppression. However, Tregs from heterozygous CD38(+/-) mice were unimpaired despite lower levels of CD38 expression. Therefore, CD38 can be used as a marker for Tregs with high suppressive activity and the impaired Treg function in p110δ(D910A) mice can in part be explained by the failure of CD38(high) cells to develop.

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PloS one, 6, 3, e17359, 2011

PMID: 21390257
DOI: 10.1371/journal.pone.0017359

Open Access

Protein kinase B controls transcriptional programs that direct cytotoxic T cell fate but is dispensable for T cell metabolism.
AN Macintyre, D Finlay, G Preston, LV Sinclair, CM Waugh, P Tamas, C Feijoo, K Okkenhaug, DA Cantrell

In cytotoxic T cells (CTL), Akt, also known as protein kinase B, is activated by the T cell antigen receptor (TCR) and the cytokine interleukin 2 (IL-2). Akt can control cell metabolism in many cell types but whether this role is important for CTL function has not been determined. Here we have shown that Akt does not mediate IL-2- or TCR-induced cell metabolic responses; rather, this role is assumed by other Akt-related kinases. There is, however, a nonredundant role for sustained and strong activation of Akt in CTL to coordinate the TCR- and IL-2-induced transcriptional programs that control expression of key cytolytic effector molecules, adhesion molecules, and cytokine and chemokine receptors that distinguish effector versus memory and naive T cells. Akt is thus dispensable for metabolism, but the strength and duration of Akt activity dictates the CTL transcriptional program and determines CTL fate.

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Immunity, 34, 2, 224-36, 2011

PMID: 21295499
DOI: 10.1016/j.immuni.2011.01.012

Open Access

Ig gene-like molecule CD31 plays a nonredundant role in the regulation of T-cell immunity and tolerance.
L Ma, C Mauro, GH Cornish, JG Chai, D Coe, H Fu, D Patton, K Okkenhaug, G Franzoso, J Dyson, S Nourshargh, FM Marelli-Berg

CD31 is an Ig-like molecule expressed by leukocytes and endothelial cells with an established role in the regulation of leukocyte trafficking. Despite genetic deletion of CD31 being associated with exacerbation of T cell-mediated autoimmunity, the contribution of this molecule to T-cell responses is largely unknown. Here we report that tumor and allograft rejection are significantly enhanced in CD31-deficient mice, which are also resistant to tolerance induction. We propose that these effects are dependent on an as yet unrecognized role for CD31-mediated homophilic interactions between T cells and antigen-presenting cells (APCs) during priming. We show that loss of CD31 interactions leads to enhanced primary clonal expansion, increased killing capacity, and diminished regulatory functions by T cells. Immunomodulation by CD31 signals correlates with a partial inhibition of proximal T-cell receptor (TCR) signaling, specifically Zap-70 phosphorylation. However, CD31-deficient mice do not develop autoimmunity due to increased T-cell death following activation, and we show that CD31 triggering induces Erk-mediated prosurvival activity in T cells either in conjunction with TCR signaling or autonomously. We conclude that CD31 functions as a nonredundant comodulator of T-cell responses, which specializes in sizing the ensuing immune response by setting the threshold for T-cell activation and tolerance, while preventing memory T-cell death.

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Proceedings of the National Academy of Sciences of the United States of America, 107, 45, 19461-6, 2010

PMID: 20978210
DOI: 10.1073/pnas.1011748107

Open Access

Phosphoinositide 3-kinase activity in T cells regulates the magnitude of the germinal center reaction.
J Rolf, SE Bell, D Kovesdi, ML Janas, DR Soond, LM Webb, S Santinelli, T Saunders, B Hebeis, N Killeen, K Okkenhaug, M Turner

The generation of high-affinity Abs is essential for immunity and requires collaboration between B and T cells within germinal centers (GCs). By using novel mouse models with a conditional deletion of the p110δ catalytic subunit of the PI3K pathway, we established that p110δ is required in T cells, but not in B cells, for the GC reaction. We found the formation of T follicular helper (T(FH)) cells to be critically dependent on p110δ in T cells. Furthermore, by deleting phosphatase and tensin homolog deleted on chromosome 10, which opposes p110δ in activated T cells, we found a positive correlation between increased numbers of T(FH) cells and GC B cells. These results are consistent with the hypothesis that T cell help is the limiting factor in the GC reaction. P110δ was not required for the expression of B cell lymphoma 6, the downregulation of CCR7, or T cell entry into primary follicles. Instead, p110δ was the critical catalytic subunit for ICOS downstream signaling and the production of key T(FH) cytokines and effector molecules. Our findings support a model in which the magnitude of the GC reaction is controlled by the activity of the PI3K pathway in T(FH) cells.

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Journal of immunology (Baltimore, Md. : 1950), 185, 7, 4042-52, 2010

PMID: 20826752
DOI: 10.4049/jimmunol.1001730

Open Access

The PI3K isoforms p110alpha and p110delta are essential for pre-B cell receptor signaling and B cell development.
F Ramadani, DJ Bolland, F Garcon, JL Emery, B Vanhaesebroeck, AE Corcoran, K Okkenhaug

B cell development is controlled by a series of checkpoints that ensure that the immunoglobulin (Ig)-encoding genes produce a functional B cell receptor (BCR) and antibodies. As part of this process, recombination-activating gene (Rag) proteins regulate the in-frame assembly of the Ig-encoding genes. The BCR consists of Ig proteins in complex with the immunoreceptor tyrosine-based activation motif (ITAM)-containing Igalpha and Igbeta chains. Whereas the activation of the tyrosine kinases Src and Syk is essential for BCR signaling, the pathways that act downstream of these kinases are incompletely defined. Previous work has revealed a key role for the p110delta isoform of phosphatidylinositol 3-kinase (PI3K) in agonist-induced BCR signaling; however, early B cell development and mature B cell survival, which depend on agonist-independent or "tonic" BCR signaling, are not substantially affected by a deficiency in p110delta. Here, we show that p110alpha, but not p110beta, compensated in the absence of p110delta to promote early B cell development in the bone marrow and B cell survival in the spleen. In the absence of both p110alpha and p110delta activities, pre-BCR signaling failed to suppress the production of Rag proteins and to promote developmental progression of B cell progenitors. Unlike p110delta, however, p110alpha did not contribute to agonist-induced BCR signaling. These studies indicate that either p110alpha or p110delta can mediate tonic signaling from the BCR, but only p110delta can contribute to antigen-dependent activation of B cells.

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Science signaling, 3, 134, ra60, 2010

PMID: 20699475
DOI: 10.1126/scisignal.2001104

Open Access

PI3Ks in lymphocyte signaling and development.
Okkenhaug K, Fruman DA

Lymphocyte development and function are regulated by tyrosine kinase and G-protein coupled receptors. Each of these classes of receptors activates phosphoinositide 3-kinase (PI3K). In this chapter, we summarize current understanding of how PI3K contributes to key aspects of the adaptive immune system.

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Current topics in microbiology and immunology, 346, 0070-217X, 57-85, 2010

PMID: 20563708

Open Access