Selective growth advantage of wild-type lymphocytes in X-linked SCID recipients.

The cytokine receptor common gamma chain (gamma c) plays a pivotal role in multiple interleukin signaling, and gamma c gene mutations cause an X-linked form of SCID (X-SCID). Recently, gamma c gene transfer into the autologous X-SCID BM achieved appreciable lymphocyte reconstitution, contrasting with the limited success in previous gene therapy trials targeting hematopoietic stem cells. To understand the mechanisms underlying this success, we examined the repopulating potential of the wild-type (WT) BM cells using an X-SCID mouse model. Limited numbers of WT cells were infused into non-ablated WT and X-SCID hosts. Whereas no appreciable engraftment was observed in WT recipients, donor-derived lymphocytes repopulated well in X-SCID, reaching 37% (10(6)cells given) and 53% (10(7) cells given) of the normal control value 5 months post BMT. A lineage analysis showed a predominance of the donor-derived lymphocytes (CD4(+) T, CD8(+) T, B and NK cells) in X-SCID while the donor-derived granulocytes and monocytes engrafted poorly. These results showed a selective advantage of WT cells in X-SCID, and that the advantage was restricted to lymphocytes. In human gene therapy for X-SCID, an analogous growth advantage would greatly enhance the repopulation of lymphocytes derived from a very small number of gamma c gene-supplemented precursors.

Expression of endothelial cell-associated molecules in AML cells.

Recently, it has been clarified that interaction between hematopoietic cells and endothelial cells is important in normal hematopoiesis and leukemogenesis. In this study, we examined the relationship between AML cells and endothelial cells by analyzing the expression profile of angiogenic factors, angiopoietin-1 (Ang-1), Ang-2, Tie-2 (a receptor for angiopoietins) and vascular endothelial growth factor (VEGF). Our results demonstrated that CD7(+)AML expressed Ang-2 mRNA frequently and integrin-family adhesion molecules (CD11c and CD18) intensively, suggesting the close correlation with endothelial cells. On the other hand, in t(8;21) AML cells, expression of Ang-2 was infrequent and expression of integrin-family adhesion molecules (CD11b, CD11c and CD18) was weak, suggesting the sparse association with endothelial cells. As for CD7(+)AML cells, despite the frequent and intense expression of endothelial cell-associated molecules (such as Ang-2, CD11c and CD18), intensity of Tie-2 expression was quite low (P < 0.05). Ang-2 expressed in CD7(+)AML cells is not considered to act in an autocrine fashion, but to work on endothelial cells to "feed" leukemic cells. Although Ang-2 is recognized as a natural antagonist for Tie-2, our data presented here suggested the alternative role of Ang-2 in the relationship between endothelial cells and leukemia cells, at least in a subset of leukemia such as CD7(+)AML. These results were supported by the study using AML cell lines, KG-1 (CD7 negative) and its subline KG-1a (CD7 positive); KG-1 had mRNA expression profile of Ang-1(+)Ang-2(-)Tie-2(+), while KG-1a showed Ang-1(+)Ang-2(+)Tie-2(-). These difference in the expression profile of angiogenic factors between CD7(+)AML and t(8;21)AML may explain the characteristic morphological features of these leukemias (CD7(+)AML as blastic type and t(8;21)AML as differentiative type).

Loss of neurons in the hippocampus and cerebral cortex of AMSH-deficient mice.

AMSH, a molecule that associates with STAM1, is involved in the in vitro cell growth signaling mediated by interleukin 2 and granulocyte-macrophage colony-stimulating factor. To investigate the in vivo functional role of AMSH, we have generated AMSH-deficient mice by gene targeting. The AMSH-deficient mice were morphologically indistinguishable from their littermates at birth, and histopathological examinations revealed normal morphogenesis in all tissues tested. However, all the AMSH-deficient mice exhibited postnatal growth retardation and died between postnatal day 19 (P19) and P23. Examination of brain sections at P6 demonstrated significant loss of neurons and apoptotic cells in the CA1 subfield of the hippocampus. Brain atrophy developed by P16 and was accompanied by complete loss of the CA1 neurons in the hippocampus and marked atrophy of the cerebral cortex. Furthermore, AMSH-deficient hippocampal neuronal cells were unable to survive in vitro, even in the presence of several stimulatory cytokines, while AMSH-deficient cerebellar neurons, thymocytes, and embryonic fibroblasts survived normally. Taken together, these observations indicate that AMSH is an essential molecule for the survival of neuronal cells in early postnatal mice.

Promoting bone morphogenetic protein signaling through negative regulation of inhibitory Smads.

Inhibitory Smads, i.e. Smad6 and Smad7, are potent antagonists of the BMP-Smad pathway by interacting with activated bone morphogenetic protein (BMP) type I receptors and thereby preventing the activation of receptor-regulated Smads, or by competing with activated R-Smads for heteromeric complex formation with Smad4. The molecular mechanisms that underlie the regulation of I-Smad activity have remained elusive. Here we report the identification of a cytoplasmic protein, previously termed associated molecule with the SH3 domain of STAM (AMSH), as a direct binding partner for Smad6. AMSH interacts with Smad6, but not with R- and Co-Smads, upon BMP receptor activation in cultured cells. Consistent with this finding, stimulation of cells with BMP induces a co-localization of Smad6 with AMSH in the cytoplasm. Ectopic expression of AMSH prolongs BMP-induced Smad1 phosphorylation, and potentiates BMP-induced activation of transcriptional reporter activity, growth arrest and apoptosis. The data strongly suggest that the molecular mechanism by which AMSH exerts its action is by inhibiting the binding of Smad6 to activated type I receptors or activated R-Smads.

Critical involvement of OX40 ligand signals in the T cell priming events during experimental autoimmune encephalomyelitis.

OX40 ligand (OX40L) expressed on APCs, and its receptor, OX40 present on activated T cells, are members of the TNF/TNFR family, respectively, and have been located at the sites of inflammatory conditions. We have observed in OX40L-deficient mice (OX40L(-/-)) an impaired APC capacity and in our recently constructed transgenic mice expressing OX40L (OX40L-Tg), a markedly enhanced T cell response to protein Ags. Using these mice, we demonstrate here the critical involvement of the OX40L-OX40 interaction during the T cell priming events in the occurrence of experimental autoimmune encephalomyelitis (EAE). In OX40L(-/-) mice, abortive T cell priming greatly reduced the clinical manifestations of actively induced EAE, coupled with a reduction in IFN-gamma, IL-2, and IL-6 production in vitro. Adoptive transfer experiments however revealed an efficient transfer of disease to OX40L(-/-) mice using wild-type donor T cells, indicating an intact capacity of OX40L(-/-) mice to initiate effector responses. On the other hand, OX40L(-/-) donor T cells failed to transfer disease to wild-type recipient mice. Furthermore, OX40L-Tg mice developed a greater severity of EAE despite a delayed onset, while both OX40L-Tg/CD28(-/-) and OX40L-Tg/CD40(-/-) mice failed to develop EAE demonstrating a requisite for these molecules. These findings indicate a pivotal role played by OX40L in the pathogenesis of EAE.

Functional CD4 T cells after intercellular molecular transfer of 0X40 ligand.

OX40/OX40 ligand (OX40L) proteins play critical roles in the T cell-B cell and T cell-dendritic cell interactions. Here we describe the intercellular transfer of OX40L molecules by a non-Ag specific manner. After 2-h coculture of activated CD4(+) T cell (OX40L(-), OX40(+)) with FLAG peptide-tagged OX40L (OX40L-flag) protein-expressing COS-1 cells, the OX40L-flag protein was detected on the cell surface of the CD4(+) T cells by both anti-OX40L and anti-FLAG mAbs. The intercellular OX40L transfer was specifically abrogated by pretreatment of the COS-1 cells with anti-OX40L mAb, 5A8. The OX40L transfer to OX40-negative cells was also observed, indicating an OX40-independent pathway of OX40L transfer. HUVECs, allostimulated monocytes, and human T cell leukemia virus type I-infected T cells, which all express OX40L, can potentially act as the donor cells of OX40L. The entire molecule of OX40L was transferred and stabilized on the recipient cell membrane with discrete punctate formation. The transferred OX40L on normal CD4(+) T cells was functionally active as they stimulated latent HIV-1-infected cells to produce viral proteins via OX40 signaling. Therefore, these findings suggest that the intercellular molecular transfer of functional OX40L may be involved in modifying the immune responses.

Human parvovirus B19 induces cell cycle arrest at G(2) phase with accumulation of mitotic cyclins.

Human parvovirus B19 infects specifically erythroid progenitor cells, which causes transient aplastic crises and hemolytic anemias. Here, we demonstrate that erythroblastoid UT7/Epo cells infected with B19 virus fall into growth arrest with 4N DNA, indicating G(2)/M arrest. These B19 virus-infected cells displayed accumulation of cyclin A, cyclin B1, and phosphorylated cdc2 and were accompanied by an up-regulation in the kinase activity of the cdc2-cyclin B1 complex, similar to that in cells treated with the mitotic inhibitor. However, degradation of nuclear lamina and phosphorylation of histone H3 and H1 were not seen in B19 virus-infected cells, indicating that the infected cells do not enter the M phase. Accumulation of cyclin B1 was persistently localized in the cytoplasm, but not in the nucleus, suggesting that B19 virus infection of erythroid cells raises suppression of nuclear import of cyclin B1, resulting in cell cycle arrest at the G(2) phase. The B19 virus-induced G(2)/M arrest may be the critical event in the damage of erythroid progenitor cells seen in patients with B19 virus infection.

Involvement of Hgs/Hrs in signaling for cytokine-mediated c-fos induction through interaction with TAK1 and Pak1.

Hgs/Hrs is a tyrosine-phosphorylated FYVE finger protein that is induced by stimulation with various cytokines and growth factors. Here we show that Hgs plays critical roles in the signaling pathway for the interleukin-2-induced activation of the serum-response element and cyclic AMP-response element of the c-fos promoter. We found that Hgs associated physically with transforming growth factor-beta-activated kinase 1 (TAK1) and p21-activated kinase 1 (Pak1), which mediate the activation of c-Jun N-terminal kinase and serum response factor, respectively, leading to transactivation via the serum-response element and cyclic AMP-response element. These results suggest that Hgs is involved in the TAK1-JNK and Pak1-serum response factor pathways for the c-fos induction that is initiated by cytokines.

Cutting edge: the common gamma-chain is an indispensable subunit of the IL-21 receptor complex.

The common gamma-chain (gamma(c)) is an indispensable subunit of the functional receptor complexes for IL-4, IL-7, IL-9, and IL-15 as well as IL-2. Here we show that the gamma(c) is also shared with the IL-21R complex. Although IL-21 binds to the IL-21R expressed on gamma(c)-deficient ED40515(-) cells, IL-21 is unable to transduce any intracytoplasmic signals. However, in EDgamma-16 cells, a gamma(c)-transfected ED40515(-) cell line, IL-21 binds to the IL-21R and can activate Janus kinase (JAK)1, JAK3, STAT1, and STAT3. The chemical cross-linking study reveals the direct binding of IL-21 to the gamma(c). These data clearly demonstrate that the gamma(c) is an indispensable subunit of the functional IL-21R complex.

Suppression of thymic development by the dominant-negative form of Gads.

Gads, a hematopoietic-lineage-specific Grb2 family member, is involved in the signaling mediated by the TCR through its interactions with SLP-76 and LAT. Here, we generated transgenic mice expressing Grf40-dSH2, an SH2-deleted dominant-negative form of Gads, which is driven by the lck proximal promoter. The total number of thymocytes was profoundly reduced in the transgenic mice, whereas in the double-negative (CD4(-)CD8(-)) thymocyte subset, in particular the CD25(+)CD44(-) pre-T cell population, it was significantly increased. However, CD5 expression, which is mediated by pre-TCR stimulation, was significantly suppressed on the CD4(-)CD8(-) thymocytes of the transgenic mice. Furthermore, the SLP-76-dependent signaling was markedly suppressed as well. These data suggest that Gads plays an important role in the pre-TCR as well as TCR signaling in thymocytes.

Loss of hippocampal CA3 pyramidal neurons in mice lacking STAM1.

STAM1, a member of the STAM (signal transducing adapter molecule) family, has a unique structure containing a Src homology 3 domain and ITAM (immunoreceptor tyrosine-based activation motif). STAM1 was previously shown to be associated with the Jak2 and Jak3 tyrosine kinases and to be involved in the regulation of intracellular signal transduction mediated by interleukin-2 (IL-2) and granulocyte-macrophage colony-stimulating factor (GM-CSF) in vitro. Here we generated mice lacking STAM1 by using homologous recombination with embryonic stem cells. STAM1(-/-) mice were morphologically indistinguishable from their littermates at birth. However, growth retardation in the third week after birth was observed for the STAM1(-/-) mice. Unexpectedly, despite the absence of STAM1, hematopoietic cells, including T- and B-lymphocyte and other hematopoietic cell populations, developed normally and responded well to several cytokines, including IL-2 and GM-CSF. However, histological analyses revealed the disappearance of hippocampal CA3 pyramidal neurons in STAM1(-/-) mice. Furthermore, we observed that primary hippocampal neurons derived from STAM1(-/-) mice are vulnerable to cell death induced by excitotoxic amino acids or an NO donor. These data suggest that STAM1 is dispensable for cytokine-mediated signaling in lymphocytes but may be involved in the survival of hippocampal CA3 pyramidal neurons.

A novel serum protein that is selectively produced by cytotoxic lymphocytes.

Cytotoxic lymphocytes such as CTL and NK cells play principal roles in the host defense mechanisms. Monitoring these effector cells in vivo is helpful to understand the immune responses in disorders such as cancer and infectious diseases. In this study, we identified a novel secretory protein, killer-specific secretory protein of 37 kDa (Ksp37), as a Th1-specific protein by a subtractive cloning method between human Th1 and Th2 cells. In peripheral blood leukocytes, Ksp37 expression was limited to Th1-type CD4(+) T cells, effector CD8(+) T cells, gammadelta T cells, and CD16(+) NK cells. Most of these Ksp37-expressing cells coexpressed perforin, indicating that Ksp37 is selectively and commonly expressed in the lymphocytes that have cytotoxic potential. Ksp37 was released at constant rate from both unstimulated and stimulated PBMCs in vitro and also detected in normal human sera. In healthy individuals, serum Ksp37 levels were significantly higher in children (mean +/- SD; 984 +/- 365 ng/ml for age 0-9) than in adults (441 +/- 135 ng/ml for age 20-99), consistent with reported differences in the absolute counts of blood T and NK cells between children and adults. In patients with infectious mononucleosis, transient elevation of serum Ksp37 levels was observed during the early acute phase of primary EBV infection. These results suggest that Ksp37 may be involved in an essential process of cytotoxic lymphocyte-mediated immunity and that Ksp37 may also have clinical value as a new type of serum indicator for monitoring cytotoxic lymphocytes in vivo.

Expression of gp34 (OX40 ligand) and OX40 on human T cell clones.

gp34, which we previously cloned, is a ligand of OX40 (CD134), a costimulatory molecule involved in T cell activation. To elucidate the role of human OX40 / OX40L interaction, we examined the expression of gp34 (OX40L) and OX40 in normal human hematopoietic cells by using flow cytometry. OX40 expression is observed on activated T cells, while OX40L is expressed in antigen-presenting cells. However, cytotoxic T lymphocyte (CTL) clones specific for Epstein-Barr virus (EBV)-transformed autologous lymphoblastic cell lines (LCLs) induced both OX40 and OX40L expression after antigen or T cell receptor (TCR) stimulation. This study suggests a possible function of OX40L / OX40, through T cell-T cell interaction, in the reactivation of memory T cells in an autocrine manner, with implications for the pathogenesis of viral infections and neoplasms.

Decreased expression of c-myc family genes in thymuses from myasthenia gravis patients.

The thymus is a critical organ for the elimination of autoreactive T cells by apoptosis. We studied the expression of apoptosis-associated genes, bcl-xL, bad, caspase-3, and c-myc family genes in myasthenia gravis (MG) thymuses. We observed that the mRNA levels of myc family genes, c-myc and max, were markedly reduced in MG thymuses. These results indicate that c-myc-mediated signaling is abnormal in MG thymuses. The levels of molecules whose expressions are associated with myc, such as STAM, prothymosin-alpha, and NFkappaB, were also analyzed.

Lack of dominant-negative effects of a truncated gamma(c) on retroviral-mediated gene correction of immunodeficient mice.

A recent clinical trial of gene therapy for X-linked severe combined immunodeficiency (XSCID) has shown that retroviral-mediated gene correction of bone marrow stem cells can lead to the development of normal immune function. These exciting results have been preceded by successful immune reconstitution in several XSCID mouse models, all carrying null mutations of the common gamma chain (gamma(c)). One question not formally addressed by these previous studies is that of possible dominant-negative effects of the endogenous mutant gamma(c) protein on the activity of the wild-type transferred gene product. The present work was therefore undertaken to study whether corrective gene transfer was applicable to an XSCID murine model with preserved expression of a truncated gammac molecule (Deltagamma(c+)-XSCID). Gene correction of Deltagamma(c+)-XSCID mice resulted in the reconstitution of lymphoid development, and preferential repopulation of lymphoid organs by gene-corrected cells demonstrated the selective advantage of gamma(c)-expressing cells in vivo. Newly developed B cells showed normalization of lipopolysaccharide-mediated proliferation and interleukin-4 (IL-4)-induced immunoglobulin G1 isotype switching. Splenic T cells and thymocytes of treated animals proliferated normally to mitogens and responded to the addition of IL-2, IL-4, and IL-7, indicating functional reconstitution of gammac-sharing receptors. Repopulated thymi showed a clear increase of CD4-/CD8- and CD8+ fractions, both dramatically reduced in untreated Deltagamma(c+)-XSCID mice. These improvements were associated with the restoration of Bcl-2 expression levels and enhanced cell survival. These data indicate that residual expression of the endogenous truncated gamma(c) did not lead to dominant-negative effects in this murine model and suggest that patient selection may not be strictly necessary for gene therapy of XSCID.

Prostaglandin D2 selectively induces chemotaxis in T helper type 2 cells, eosinophils, and basophils via seven-transmembrane receptor CRTH2.

Prostaglandin (PG)D2, which has long been implicated in allergic diseases, is currently considered to elicit its biological actions through the DP receptor (DP). Involvement of DP in the formation of allergic asthma was recently demonstrated with DP-deficient mice. However, proinflammatory functions of PGD2 cannot be explained by DP alone. We show here that a seven-transmembrane receptor, CRTH2, which is preferentially expressed in T helper type 2 (Th2) cells, eosinophils, and basophils in humans, serves as the novel receptor for PGD2. In response to PGD2, CRTH2 induces intracellular Ca2+mobilization and chemotaxis in Th2 cells in a Galphai-dependent manner. In addition, CRTH2, but not DP, mediates PGD2-dependent cell migration of blood eosinophils and basophils. Thus, PGD2 is likely involved in multiple aspects of allergic inflammation through its dual receptor systems, DP and CRTH2.

Characterization of the gammac chain among 27 unrelated Japanese patients with X-linked severe combined immunodeficiency (X-SCID).

X-linked severe combined immunodeficiency (X-SCID) is a rare fatal disease that is caused by mutations in the gene encoding the gammac chain. In this study, 27 unrelated Japanese patients with X-SCID were examined in terms of their genetic mutations and surface expression of the gammac chain. Among 25 patients examined, excluding two patients with large deletions, 23 different mutations were identified in the IL2RG gene, including 10 novel mutations. One patient bearing an extracellular mutation and all three of the patients bearing intracellular mutations after exon 7 expressed the gammac chain on the cell surface. Overall, 84% of patients lacked surface expression of the gammac chain leading to a diagnosis of X-SCID.

Expression of OX40 and OX40 ligand (gp34) in the normal and myasthenic thymus.

OBJECTIVES: To examine the expression of OX40, an activated memory T-cell marker, and its ligand (OX40L), a set of molecules for T-cell-B-cell interaction, and other lymphocyte activation markers in the thymuses of myasthenia gravis (MG) and controls. MATERIAL AND METHODS: We studied the expression of OX40, OX40L, IL-2Ralpha and HLA-DR in the thymic tissues of MG and controls using immunocytochemistry and flowcytometry. RESULTS: In both hyperplastic thymus of MG and control thymus, OX40+ cells were scattered mainly in the medulla with much fewer OX40L+ cells being distributed in the corticomedullary junctions. IL-2Ralpha and HLA-DR were expressed in the medulla at higher frequencies as compared with OX40 in controls as well as MG. In contrast, the numbers of OX40+ cells around the germinal centers (GC) were significantly greater than those of control thymuses, and some mononuclear cells in GC were OX40L+. A considerable number of OX40+ cells were seen in the thymic tissues adjacent to thymomas. OX40+ cells were CD4+ CD8- or CD4+ CD8+ and were mostly HLA-DR-. (The coexpression of OX40 and IL-2Ralpha on activated CD4+ T cells was previously reported.) CONCLUSION: OX40, expressed in a fraction of activated CD4+ T cells, may be upregulated in thymic tissues adjacent to GC and thymoma in MG, and OX40 may interact with OX40L in GC to enhance anti-acetylcholine receptor antibody production in MG.