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John J O'Shea

Publications and source records attributed to John J O'Shea.

At least 19 recordsLinked to original sources
PubMed2007

Helper T cell IL-2 production is limited by negative feedback and STAT-dependent cytokine signals.

Although required for many fundamental immune processes, ranging from self-tolerance to pathogen immunity, interleukin (IL)-2 production is transient, and the mechanisms underlying this brevity remain unclear. These studies reveal that helper T cell IL-2 production is limited by a classic negative feedback loop that functions autonomously or in collaboration with other common gamma chain (IL-4 and IL-7) and IL-6/IL-12 family cytokines (IL-12 and IL-27). Consistent with this model for cytokine-dependent regulation, they also demonstrate that the inhibitory effect can be mediated by several signal transducer and activator of transcription (STAT) family transcription factors, namely STAT5, STAT4, and STAT6. Collectively, these findings establish that IL-2 production is limited by a network of autocrine and paracrine signals that are readily available during acute inflammatory responses and, thus, provide a cellular and molecular basis for its transient pattern of expression.

Animals↗
PubMed2007

Nonredundant roles for Stat5a/b in directly regulating Foxp3.

Stats (signal transducers and activators of transcription) regulate multiple aspects of T-cell fate. T regulatory (Treg) cells are a critical subset that limits immune responses, but the relative importance of Stat5a/b versus Stat3 for Treg cell development has been contentious. We observed that peripheral CD25(+)CD4(+) T cells were reduced in Stat5(DeltaN) mice; however, the levels of Foxp3, a transcription factor that is critical for Treg cells, were normal in splenic CD4(+) T cells even though they were reduced in the thymus. In contrast, complete deletion of Stat5a/b (Stat5(-/-)) resulted in dramatic reduction in CD25- or Foxp3-expressing CD4(+) T cells. An intrinsic requirement was demonstrated by reduction of Stat5a/b in CD4-expressing cells and by stem cell transplantation using Stat5(-/-) fetal liver cells. Stat5a/b were also required for optimal induction of Foxp3 in vitro and bound directly to the Foxp3 gene. Reduction of Stat3 in T cells did not reduce the numbers of Treg cells in the thymus or spleen; however, Stat3 was required for IL-6-dependent down-regulation of Foxp3. Therefore, we conclude that Stat5a/b have an essential, nonredundant role in regulating Treg cells, and that Stat3 and Stat5a/b appear to have opposing roles in the regulation of Foxp3.

Animals↗
PubMed2007

T cell-directed therapies: lessons learned and future prospects.

Agents interfering with T cell function are therapeutic mainstays for various autoimmune diseases and for transplant approaches to organ failure. The understanding of T cell biology has blossomed since the development of most agents now in use. Here we discuss T cell-specific agents now in use, others recently added to the therapeutic armamentarium and promising agents being investigated in clinical and preclinical studies. In addition, we reflect on the risks and benefits involved in the testing of such agents clinically, with examples of agents that have successfully been used in the clinic and agents that failed to reach therapeutic use.

Cell Adhesion↗
PubMed2006

Interleukin 27 negatively regulates the development of interleukin 17-producing T helper cells during chronic inflammation of the central nervous system.

Studies have focused on the events that influence the development of interleukin 17 (IL-17)-producing T helper cells (T(H)-17 cells) associated with autoimmunity, such as experimental autoimmune encephalitis, but relatively little is known about the cytokines that antagonize T(H)-17 cell effector responses. Here we show that IL-27 receptor-deficient mice chronically infected with Toxoplasma gondii developed severe neuroinflammation that was CD4+ T cell dependent and was associated with a prominent IL-17 response. In vitro, treatment of naive primary T cells with IL-27 suppressed the development T(H)-17 cells induced by IL-6 and transforming growth factor-beta, which was dependent on the intracellular signaling molecule STAT1 but was independent of inhibition of IL-6 signaling mediated by the suppressor protein SOCS3. Thus IL-27, a potent inhibitor of T(H)-17 cell development, may be a useful target for treating inflammatory diseases mediated by these cells.

Animals↗
PubMed2006

Selective regulatory function of Socs3 in the formation of IL-17-secreting T cells.

Suppressor of cytokine signaling (Socs) 3 is a cytokine-inducible inhibitor with critical but selective cell-specific effects. We show that deficiency of Socs3 in T cells had minimal effects on differentiation of T cells to the T helper (Th) 1 or Th2 subsets; accordingly, Socs3 had no effect on IL-12-dependent signal transducer and activator of transcription (Stat) 4 phosphorylation or IL-4-dependent Stat6 phosphorylation. By contrast, Socs3 was found to be a major regulator of IL-23-mediated Stat3 phosphorylation and Th17 generation, and Stat3 directly binds to the IL-17A and IL-17F promoters. We conclude that Socs3 is an essential negative regulator of IL-23 signaling, inhibition of which constrains the generation of Th17 differentiation.

Animals↗
PubMed2006

Proprotein convertase furin is preferentially expressed in T helper 1 cells and regulates interferon gamma.

Interleukin 12 (IL-12) is a major inducer of interferon gamma (IFN-gamma) and the principal mediator of T helper 1 (Th1) differentiation. To identify IL-12-regulated genes, which might contribute to Th1 differentiation and IFNG regulation, we employed microarray analysis. Surprisingly, a ubiquitously expressed proprotein convertase (PC), furin, was one of the most consistently IL-12-induced genes in T cells, and among PCs was the only one regulated by this cytokine. Furin was preferentially expressed in differentiated Th1 cells in a Stat4-dependent manner. Expression of furin enhanced IFN-gamma secretion, whereas inhibition of furin interfered with IFN-gamma production. Thus, we conclude that IL-12 induction of furin might represent a new aspect of IFN-gamma regulation and control of Th1 differentiation.

Cell Differentiation↗
PubMed2006

Helper T cell differentiation enters a new era: le roi est mort; vive le roi!

In the dark ages of T cell biology, we considered two fates for differentiated CD4+ T cells: T helper (Th)1 and Th2 cells. Now we know that the reality is much more complex and interesting. The newest Th cell subset produces the cytokine IL-17. New evidence shows that the IL-17-related cytokine IL-25 is essential for Th2 responses in two infectious disease models.

Animals↗
PubMed2006

T-bet regulates Th1 responses through essential effects on GATA-3 function rather than on IFNG gene acetylation and transcription.

T helper type 1 (Th1) development is facilitated by interrelated changes in key intracellular factors, particularly signal transducer and activator of transcription (STAT)4, T-bet, and GATA-3. Here we show that CD4+ cells from T-bet-/- mice are skewed toward Th2 differentiation by high endogenous GATA-3 levels but exhibit virtually normal Th1 differentiation provided that GATA-3 levels are regulated at an early stage by anti-interleukin (IL)-4 blockade of IL-4 receptor (R) signaling. In addition, under these conditions, Th1 cells from T-bet-/- mice manifest IFNG promotor accessibility as detected by histone acetylation and deoxyribonuclease I hypersensitivity. In related studies, we show that the negative effect of GATA-3 on Th1 differentiation in T-bet-/- cells arises from its ability to suppress STAT4 levels, because if this is prevented by a STAT4-expressing retrovirus, normal Th1 differentiation is observed. Finally, we show that retroviral T-bet expression in developing and established Th2 cells leads to down-regulation of GATA-3 levels. These findings lead to a model of T cell differentiation that holds that naive T cells tend toward Th2 differentiation through induction of GATA-3 and subsequent down-regulation of STAT4/IL-12Rbeta2 chain unless GATA-3 levels or function is regulated by T-bet. Thus, the principal function of T-bet in developing Th1 cells is to negatively regulate GATA-3 rather than to positively regulate the IFNG gene.

Acetylation↗
PubMed2006

Stat5a/b are essential for normal lymphoid development and differentiation.

Cytokines that use the common gamma chain gammac are critical for lymphoid development and function. Mutations of the IL-7 receptor, gammac, or its associated kinase, Jak3, are the major cause of human severe combined immunodeficiency. Although activated by IL-7, Stat5a/b (Stat, signal transducer and activator of transcription) have been thought to play limited roles in lymphoid development. However, we now show that mice completely deficient in Stat5a/b have severely impaired lymphoid development and differentiation. Absence of Stat5 also abrogates T cell receptor gamma rearrangement and survival of peripheral CD8(+) T cells. Thus, deficiency of Stat5 results in severe combined immunodeficiency, similar in many respects to deficiency of IL-7R, gammac, and Jak3.

Animals↗
PubMed2006

Cytohesin binder and regulator (cybr) is not essential for T- and dendritic-cell activation and differentiation.

Cybr (also known as Cytip, CASP, and PSCDBP) is an interleukin-12-induced gene expressed exclusively in hematopoietic cells and tissues that associates with Arf guanine nucleotide exchange factors known as cytohesins. Cybr levels are dynamically regulated during T-cell development in the thymus and upon activation of peripheral T cells. In addition, Cybr is induced in activated dendritic cells and has been reported to regulate dendritic cell (DC)-T-cell adhesion. Here we report the generation and characterization of Cybr-deficient mice. Despite the selective expression in hematopoietic cells, there was no intrinsic defect in T- or B-cell development or function in Cybr-deficient mice. The adoptive transfer of Cybr-deficient DCs showed that they migrated efficiently and stimulated proliferation and cytokine production by T cells in vivo. However, competitive stem cell repopulation experiments showed a defect in the abilities of Cybr-deficient T cells to develop in the presence of wild-type precursors. These data suggest that Cybr is not absolutely required for hematopoietic cell development or function, but stem cells lacking Cybr are at a developmental disadvantage compared to wild-type cells. Collectively, these data demonstrate that despite its selective expression in hematopoietic cells, the role of Cybr is limited or largely redundant. Previous in vitro studies using overexpression or short interfering RNA inhibition of the levels of Cybr protein appear to have overestimated its immunological role.

Animals↗
PubMed2005

IFN regulatory factor-4 and -8 govern dendritic cell subset development and their functional diversity.

Dendritic cells (DCs) are bone marrow (BM)-derived APCs central to both innate and adaptive immunity. DCs are a heterogeneous cell population composed of multiple subsets with diverse functions. The mechanism governing the generation of multiple DC subsets is, however, poorly understood. In this study we investigated the roles of closely related transcription factors, IFN regulatory factor (IRF)-4 and IRF-8, in DC development by analyzing IRF-4(-/-), IRF-8(-/-), and IRF-4(-/-)IRF-8(-/-) (double-knockout) mice. We found that IRF-4 is required for the generation of CD4(+) DCs, whereas IRF-8 is, as reported previously, essential for CD8alpha(+) DCs. Both IRFs support the development of CD4(-)CD8alpha(-) DCs. IRF-8 and, to a lesser degree, IRF-4 contribute to plasmacytoid DC (PDC) development. Thus, the two IRFs together regulate the development of all conventional DCs as well as PDCs. Consistent with these findings, IRF-4, but not IRF-8, was expressed in CD4(+) DCs, whereas only IRF-8 was expressed in CD8alpha(+) DCs. CD4(-)CD8alpha(-) DCs and PDCs expressed both IRFs. We also demonstrate in vitro that GM-CSF-mediated DC differentiation depends on IRF-4, whereas Fms-like tyrosine kinase 3 ligand-mediated differentiation depends mainly on IRF-8. Gene transfer experiments with double-knockout BM cells showed that both IRFs have an overlapping activity and stimulate a common process of DC development. Nonetheless, each IRF also possesses a distinct activity to stimulate subset-specific gene expression, leading to the generation of functionally divergent DCs. Together, IRF-4 and IRF-8 serve as a backbone of the molecular program regulating DC subset development and their functional diversity.

Animals↗
PubMed2005

New strategies for immunosuppression: interfering with cytokines by targeting the Jak/Stat pathway.

PURPOSE OF REVIEW: Numerous immunosuppressants are available, but their adverse effects related to actions on nonlymphoid cells is problematic. Cytokines are key regulators of immune and inflammatory responses, and blocking their actions has become an important modality in treating autoimmune disorders. This review will discuss strategies to develop novel immunosuppressants that arise from advances in the understanding of cytokine signaling. RECENT FINDINGS: It is now recognized that large number of cytokines exert their effect by binding to receptors that activate the Janus kinase/signal transducer and activator of transcription pathway, so targeting intracellular signaling pathways is a logical strategy. A selective inhibitor of Janus kinase 3 has now been generated and is effective for transplant rejection in nonhuman primates and other models. Advances have also been made in understanding the functions of Stat family transcription factors, and approaches to interfering with the action of these DNA binding proteins are being devised. In addition, the identification of negative regulators of cytokine signaling offers additional therapeutic opportunities. SUMMARY: A selective inhibitor of Janus kinase 3 has now been generated and likely represents a new class of effective immunosuppressants. Strategies for targeting signal transducers and activators of transcription pathway are being intensively studied at present and hold potential promise. Multiple endogenous mechanisms exist for negatively regulating cytokine signaling; whether novel therapies can be devised that exploit these mechanisms remains to be determined.

Animals↗
PubMed2005

Jak3, severe combined immunodeficiency, and a new class of immunosuppressive drugs.

The recent elucidation of the multiple molecular mechanisms underlying severe combined immunodeficiency (SCID) is an impressive example of the power of molecular medicine. Analysis of patients and the concomitant generation of animal models mimicking these disorders have quickly provided great insights into the pathophysiology of these potentially devastating illnesses. In this review, we summarize the discoveries that led to the understanding of the role of cytokine receptors and a specific tyrosine kinase, Janus kinase 3 (Jak3), in the pathogenesis of SCID. We discuss how the identification of mutations of Jak3 in autosomal recessive SCID has facilitated the diagnosis of these disorders, offered new insights into the biology of this kinase, permitted new avenues for therapy, and provided the rationale for a generation of a new class of immunosuppressants.

Humans↗
PubMed2004

CXCL12 signaling is independent of Jak2 and Jak3.

Janus kinases (Jaks) are a small family of cytoplasmic tyrosine kinases, critical for signaling by Type I and II cytokine receptors. The importance of Jaks in signaling by these receptors has been firmly established by analysis of mutant cell lines, the generation of Jak knock-out mice, and the identification of patients with Jak3 mutations. While a number of other ligands that do not bind Type I and II cytokine receptors have also been reported to activate Jaks, the requirement for Jaks in signaling by these receptors is less clear. Chemokines for example, which bind seven transmembrane receptors, have been reported to activate Jaks, and principally through the use of pharmacological inhibitors, it has been argued that Jaks are essential for chemokine signaling. In the present study, we focused on CXCR4, which binds the chemokine CXCL12 or stromal cell-derived factor-1, a chemokine that has been reported to activate Jak2 and Jak3. We found that the lack of Jak3 had no effect on CXCL12 signaling or chemotaxis nor did overexpression of wild-type versions of the kinase. Similarly, overexpression of wild-type or catalytically inactive Jak2 or "knocking-down" Jak2 expression using siRNA also had no effect. We also found that in primary lymphocytes, CXCL12 did not induce appreciable phosphorylation of any of the Jaks compared with cytokines for which these kinases are required. Additionally, little or no Stat (signal transducer and activator of transcription) phosphorylation was detected. Thus, we conclude that in contrast to previous reports, Jaks, especially Jak3, are unlikely to play an essential role in chemokine signaling.

Blotting, Western↗
PubMed2004

The Janus kinases (Jaks).

The Janus kinase (Jak) family is one of ten recognized families of non-receptor tyrosine kinases. Mammals have four members of this family, Jak1, Jak2, Jak3 and Tyrosine kinase 2 (Tyk2). Birds, fish and insects also have Jaks. Each protein has a kinase domain and a catalytically inactive pseudo-kinase domain, and they each bind cytokine receptors through amino-terminal FERM (Band-4.1, ezrin, radixin, moesin) domains. Upon binding of cytokines to their receptors, Jaks are activated and phosphorylate the receptors, creating docking sites for signaling molecules, especially members of the signal transducer and activator of transcription (Stat) family. Mutations of the Drosophila Jak (Hopscotch) have revealed developmental defects, and constitutive activation of Jaks in flies and humans is associated with leukemia-like syndromes. Through the generation of Jak-deficient cell lines and gene-targeted mice, the essential, nonredundant functions of Jaks in cytokine signaling have been established. Importantly, deficiency of Jak3 is the basis of human autosomal recessive severe combined immunodeficiency (SCID); accordingly, a selective Jak3 inhibitor has been developed, forming a new class of immunosuppressive drugs.

Animals↗