Requirement for IFN-gamma in IL-12 production induced by collaboration between v(alpha)14(+) NKT cells and antigen-presenting cells

Two cytokines IL-4 and IL-12 are known to determine the balance between T(h)1 and T(h)2 development. In addition to IL-4 production of V(alpha)14(+) NKT cells, they have recently been demonstrated to have the capacity to stimulate IL-12 production by antigen-presenting cells (APC). This study demonstrates that IFN-gamma is absolutely required for the NKT cell-stimulated IL-12 production. Culture of B cell-depleted spleen cells from C57BL/6 mice with alpha-galactosylceramide (alpha-GalCer) capable of selectively stimulating V(alpha)14/J(alpha)281(+) NKT cells resulted in the production of IL-12 together with IL-4. Whereas IL-4 production occurred in culture of IFN-gamma(-/-) C57BL/6 splenocytes, the same culture failed to generate IL-12 production. While IL-12 production induced during culture of V(alpha)14(+) NKT cells and APC depended on the interaction between CD40 ligand on NKT cells and CD40 on APC, the expression levels of these key molecules were comparable in cells from wild-type and IFN-gamma(-/-) mice. Addition of rIFN-gamma to alpha-GalCer stimulated IFN-gamma(-/-) splenocyte culture, and administration of rIFN-gamma to alpha-GalCer-injected IFN-gamma(-/-) mice resulted in the restoration of IL-12 production in vitro and in vivo. These results illustrate a mandatory role for IFN-gamma in V(alpha)14(+) NKT cell-stimulated IL-12 production by APC.

Tumor vaccination that enhances antitumor T-cell responses does not inhibit the growth of established tumors even in combination with interleukin-12 treatment: the importance of inducing intratumoral T-cell migration

Interleukin-12 (IL-12) treatment is effective in the CSA1M but not in the Meth A and CSA1M-variant tumor models. The authors investigated the cause by which IL-12 treatment fails to induce tumor regression in these two tumor models. T cells from CSA1M-bearing mice have high levels of IL-12 responsiveness, whereas cells from Meth A-bearing mice display marginal levels of responsiveness. Because IL-12 responsiveness in T cells is induced after T-cell receptor stimulation, the lack of IL-12 responsiveness suggests that T cells in Meth A-bearing mice are not sensitized to Meth A tumor antigen. Immunization of normal mice with attenuated Meth A tumor cells resulted in a protective immunity, as shown by the rejection of challenged viable Meth A cells. Such an immunization, when performed in Meth A-bearing mice, induced potent IL-12 responsiveness in T cells. Nevertheless, IL-12 treatment in these mice did not inhibit tumor growth. In another IL-12-incurable (CSA1M-variant) model, IL-12 responsiveness was observed before tumor cell immunization. However, IL-12 treatment was ineffective regardless of whether tumor cell immunization was performed. In these two models, the failure of IL-12 treatment to induce tumor regression was associated with the lack of T-cell migration to tumor sites. These results indicate that the sensitization of T cells to tumor antigens and generation of IL-12 responsiveness are insufficient to induce tumor regression when these sensitized T cells are not allowed to migrate to tumor sites.

Effects of epinephrine and lactate on the increase in oxygen consumption of nonexercising skeletal muscle after aerobic exercise

The purpose of this study was to measure O2 consumption of nonexercising skeletal muscles (VO2nonex) at rest and after aerobic exercise and to investigate the stimulant factors of O2 consumption. In experiment 1, we measured the resting metabolic rate of the finger flexor muscles in seven healthy males by 31P-magnetic resonance spectroscopy during a 15 min arterial occlusion. In experiment 2, the VO2nonex of the finger flexor muscles was measured using near infrared continuous wave spectroscopy at rest, immediate postexercise, and 3, 5, 10, 15, and 20 min following a cycling exercise at a workload corresponding to 50% of peak pulmonary O2 uptake for 20 min. We also monitored deep tissue temperature in the VO2nonex measurement area and determined catecholamines and lactate concentrations in the blood at rest and immediate postexercise. VO2nonex at rest was 1.1 +/- 0.1 microM O2/S (mean +/- standard error) and VO2nonex after exercise increased 59.6 +/- 7.2% (p < 0.001) from the resting values. There were significant correlations between the increase in VO2nonex and the increase in epinephrine concentration (p < 0.01), and between the increase in VO2nonex and the increase in lactate concentration (p < 0.05). These results suggest that epinephrine and lactate concentrations are important VO2nonex stimulant factors.

Serine 6 of Lck tyrosine kinase: a critical site for Lck myristoylation, membrane localization, and function in T lymphocytes

Lck is a member of the Src family kinases expressed predominantly in T cells, and plays a pivotal role in TCR-mediated signal transduction. Myristoylation of glysine 2 in the N-terminal Src homology 4 (SH4) domain of Lck is essential for membrane localization and function. In this study, we examined a site within the SH4 domain of Lck regulating myristoylation, membrane localization, and function of Lck. A Lck mutant in which serine 6 (Ser6) was substituted by an alanine was almost completely cytosolic in COS-7 cells, and this change of localization was associated with a drastic inhibition of myristoylation in this mutant. To assess the role of Ser6 of Lck in T cell function, we established stable transfectants expressing various Lck mutants using Lck-negative JCaM1 cells. The Lck mutant of Ser6 to alanine, most of which did not target to the plasma membrane, was not able to reconstitute TCR-mediated signaling events in JCaM1 cells, as analyzed by tyrosine phosphorylation of intracellular proteins and CD69 expression. These results demonstrate that Ser6 is a critical factor for Lck myristoylation, membrane localization, and function in T cells, presumably because the residue is important for N-myristoyl transferase recognition.

Differential effects of N-acetyl-l-cysteine on IL-2- vs IL-12-driven proliferation of a T cell clone: implications for distinct signalling pathways

Using a T cell clone (2D6) capable of responding to IL-2 and IL-12, we compared the effects of NAC on IL-2 and IL-12-driven T cell proliferation. Addition of N-acetylcysteine (NAC) to 2D6 cultures did not affect IL-2 stimulated proliferation, but strikingly inhibited IL-12 stimulated proliferation. These differential NAC effects did not correlate with the patterns of the mitogen-activated protein kinase (MAPK) activation following cytokine stimulation and its regulation by NAC. Although a p38 MAPK inhibitor downregulated both IL-2- and IL-12-induced proliferation, this effect was seen at drug concentrations one order higher than those reportedly used to specifically inhibit p38 MAPK. The results suggest the existence of distinct signalling pathways and a common, indispensable signalling molecule in IL-2- and IL-12 driven T cell proliferation.

Near-infrared spectroscopy: what can it tell us about oxygen saturation in skeletal muscle?

Near-infrared spectroscopy (NIRS) measures hemoglobin saturation in small vessels. A number of interesting studies have used this method. However, difficulties with signal quantification and studies in which NIRS oxygen saturation did not behave as expected raise concerns. NIRS remains promising for studies of skeletal muscle, but a better understanding of the method is needed.

MCF-7 growth inhibition by ultraviolet radiation and 5-fluorouracil: the importance of treatment sequence

Effective treatment of certain cancers with 5-fluorouracil (5-FU) and irradiation is well established; however, the most effective combination of these agents remains controversial. Although 5-FU has been identified as a radiosensitizer, the mechanism of action remains unknown. To assess the effect of combination, 5-FU and ultraviolet (UV), we constructed a new in vitro model with MCF-7 human breast cancer cells that measures growth inhibition and morphologic changes in nuclear argyrophilic nucleolar organizer regions (AgNORs). Cells were incubated in media containing 0, 50, 100 and 500 ng/ml 5-FU for 48 h, they were also exposed to UV irradiation of 90 J/m(2) at the beginning, middle, or end of the incubation period. The cells were incubated for an additional 48 h with 5-FU free media. A combined treatment with 5-FU and UV radiation demonstrated an additive inhibitory effect. The strongest growth inhibition was observed when UV exposure was at the beginning of the 5-FU treatment at 5-FU concentrations of 100 and 500 ng/ml. To elucidate the activity of 5-FU radiosensitization, we investigated the aggregation Pof AgNOR, which we previously established to reflect rRNA inhibition. A combined treatment with 5-FU and UV radiation accelerated the rate of AgNOR aggregation at 5-FU concentrations of 50 and 100 ng/ml. The timing of UV irradiation did not affect the rate of AgNOR aggregation. A combined treatment with 5-FU and UV radiation showed an additive inhibitory effect on MCF-7 cell growth that might be explained, in part, by rRNA inhibition.

Fusogenic liposomes efficiently deliver exogenous antigen through the cytoplasm into the MHC class I processing pathway

Exogenous soluble proteins enter the endosomal pathway by endocytosis and are presented in association with MHC class II rather than class I. In contrast, the delivery of exogenous protein antigens (Ag) into the cytosol generates MHC class I-restricted cytotoxic T lymphocytes (CTL) responses. Although several immunization approaches, such as the utilization of liposomes, have induced the in vivo priming of MHC class I-restricted CTL responses to protein Ag, it remains unclear whether this priming results from the direct delivery of protein Ag to the cytosol. Here we report that fusogenic liposomes (FL), which are prepared by fusing simple liposomes with Sendai virus particles, can deliver the encapsulated soluble protein directly into the cytosol of cells cultured concurrently and introduce it into the conventional MHC class I Ag presentation pathway. Moreover, a single immunization with ovalbumin (OVA) encapsulated in FL but not in simple liposomes results in the potent priming of OVA-specific CTL. Thus, FL function as an efficient tool for the delivery of CTL vaccines.

Differential IL-12 responsiveness of T cells but not of NK cells from tumor-bearing mice in IL-12-responsive versus -unresponsive tumor models

While IL-12 administration induces tumor regression through stimulating T cells in tumor-bearing mice, this IL-12 effect is observed in some but not all tumor models. The present study aimed to compare IL-12 responsiveness of T cells from tumor-bearing mice in IL-12-responsive (CSA1M and OV-HM) and -unresponsive (Meth A) tumor models. Tumor regression in IL-12-responsive tumor models required the participation of T cells, but not of NK1.1(+) cells. Because a NK1.1(+) cell population was the major producer of IFN-gamma, comparable levels of IFN-gamma production were induced in IL-12-responsive and -unresponsive tumor-bearing mice. This indicates that the amount of IFN-gamma produced in tumor-bearing individuals does not correlate with the anti-tumor efficacy of IL-12. In contrast, IL-12 responsiveness of T cells differed between the responsive and unresponsive models: purified T cells from CSA1M/OV-HM-bearing or Meth A-bearing mice exhibited high or low IL-12 responsiveness respectively, when evaluated by the amounts of IFN-gamma produced in response to IL-12. T cells from CSA1M- or OV-HM-bearing but not from Meth A-bearing mice exhibited enhanced levels of mRNA for the IL-12 receptor (IL-12R). These results indicate that a fundamental difference exists in IL-12 responsiveness of T cells between IL-12-responsive and -unresponsive tumor models, and that such a difference is associated with the expression of IL-12R on T cells.

A novel function of B lymphocytes from normal mice to suppress autoimmunity in (NZB x NZW)F1 mice

In systemic autoimmune-prone (NZB x NZW)F1 (NZB/W F1) mice, B-cell abnormalities characterized by hypergammaglobulinaemia accompanying autoantibodies have been thought to be a main cause of the disease. To examine a possible regulatory role of B cells in the disease manifestations, we injected, intravenously (i.v.), normal or autoimmune B cells into non-irradiated NZB/W F1 mice. The injection of splenic B cells from major histocompatibility (MHC)-matched or allogeneic normal mice caused a marked decrease in serum immunoglobulin G (IgG) levels of autoantibodies, delayed the appearance of proteinuria and prolonged life span, whereas treatment with splenic B cells from NZB/W F1 or X-linked immunodeficient (Xid) mice failed to suppress the autoimmunity. Moreover, in vitro polyclonal antibody responses to lipopolysaccharide (LPS) of NZB/W F1-derived B cells from the treated mice were markedly reduced. Interestingly, the treatment of NZB/W F1 mice at 16, 18 and 20 or at 20, 22 and 24 weeks of age was more effective than that at 6, 8 and 10 weeks. The treatment also inhibited the development of surface IgG+ (sIgG+) B cells and splenomegaly, prominent in aged NZB/W F1 mice. In addition, when untreated NZB/W F1 responding B cells were precultured with normal B cells in vitro for 3 days, they also diminished the autoantibody production to subsequent LPS stimulation. Hence, the present results imply a novel function of normal B cells to ameliorate autoimmune disease in NZB/W F1 mice by correcting their B-cell abnormalities, and indicate that NZB/W F1 and Xid mice possess defects in this regulatory B-cell function.

Comparison of muscle oxygen consumption measured by near infrared continuous wave spectroscopy during supramaximal and intermittent pedalling exercise

The two purposes of the present study were 1) to determine the oxygen consumption in working skeletal muscle from the oxygenation measured by near-infrared continuous-wave spectroscopy (NIRcws) with the arterial occlusion method during the resting condition, INT(VT), and INT(MAX) and 2) to examine whether the decline rate of oxygenation is related to maximal oxygen uptake. Eight healthy males (aged 19.8 +/- 0.4 yr, height 166.9 +/- 17.4 cm, weight 62.1 +/- 2.5 kg, and maximal oxygen uptake [VO2max] 55.9 +/- 1.9 ml/kg x min(-1)) took part in this study. The oxygenation was measured by NIRcws during the Wingate anaerobic test (WAnT) and two intermittent pedalling exercises of VT (INT(VT)) and maximal (INT(MAX)) work intensity. The decline rates of oxygenation obtained during the resting condition, INT(VT), and INT(MAX) with arterial occlusion were 0.43 +/- 0.05%/sec, 4.94 +/- 0.31%/sec, and 8.16 +/- 0.38%/sec, respectively, and that during the WAnT without arterial occlusion was 8.73 +/- 0.49%/sec. The decline rate of oxygenation during the WAnTwas significantly (p < 0.0001) related to maximal oxygen uptake (VO2max). These findings indicate that O2 is utilized from the early phase, even during a supramaximal pedalling exercise, and that the oxidative metabolic capacity may be a factor contributing to supramaximal exercises. Therefore the arterial occlusion method with NIRcws is suitable for the evaluation of the muscle O2 consumption during exercise noninvasively.

The development of peritumoral stroma required for IL-12 induced tumor regression depends on the T cell/IFN-gamma-involving host-tumor interaction

T cell migration into tumor masses is a critical process in the scenario of IL-12-induced tumor regression. Our previous study showed that this depends on the development of peritumoral stroma prior to IL-12 therapy. The present study investigated the regulation of the development of peritumoral stroma in comparison with tumor-parenchymal stroma. In the OV-HM and CSA1M tumor models, tumor regression associated with T cell migration was induced following IL-12 treatment. Both OV-HM and CSA1M tumor masses growing in syngeneic mice developed peritumoral stroma before IL-12 treatment. However, peritumoral stroma was not observed in these two types of tumor masses generated in nude mice, T cell-depleted syngeneic mice, anti-IFN-gamma mAb-treated mice or IFN-gamma-deficient mice. In contrast, parenchymal stroma formation did not appear to be affected because tumors generated in these groups of mice exhibited rather higher growth rates than those of tumors in normal syngeneic mice. Importantly, the lack of peritumoral stroma in tumor masses was associated with the failure of T cells to migrate to these tumor masses: splenic T cells prepared from IL-12-treated tumor-bearing mice migrated into the corresponding tumor mass growing in untreated syngeneic recipient mice, whereas portions of the same donor cells failed to migrate into the above stroma-negative tumor masses. These results indicate that the development of peritumoral and parenchymal stroma is differentially regulated; there exist functional differences in the two types of stroma; and the formation of peritumoral stroma requires components of the host's immune system such as IFN-gamma and T cells.

The inhibitory effect of interferon gamma and tumor necrosis factor alpha on intracellular multiplication of Neospora caninum in primary bovine brain cells

Primary culture of bovine brain cells was examined for its susceptibility to Neospora caninum infections, and this model was used to investigate the effects of bovine interferon gamma (IFN-gamma) and tumor necrosis factors alpha (TNF-alpha) on tachyzoite growth. Tachyzoites of N. caninum grew well in this culture, and tachyzoite growth in astroglia and microglia were confirmed by immunocytochemical staining. IFN-gamma inhibited the tachyzoite growth, and this inhibition was not reversed by the addition of nitric oxide antagonist. TNF-alpha, to a lesser extent, also inhibited the tachyzoite growth. Th-1 type cytokines may play an important role in host defense mechanisms in N. caninum infection.

Non-CD28 costimulatory molecules present in T cell rafts induce T cell costimulation by enhancing the association of TCR with rafts

While CD28 functions as the major T cell costimulatory receptor, a number of other T cell molecules have also been described to induce T cell costimulation. Here, we investigated the mechanisms by which costimulatory molecules other than CD28 contribute to T cell activation. Non-CD28 costimulatory molecules such as CD5, CD9, CD2, and CD44 were present in the detergent-insoluble glycolipid-enriched (DIG) fraction/raft of the T cell surface, which is rich in TCR signaling molecules and generates a TCR signal upon recruitment of the TCR complex. Compared with CD3 ligation, coligation of CD3 and CD5 as an example of DIG-resident costimulatory molecules led to an enhanced association of CD3 and DIG. Such a DIG redistribution markedly up-regulated TCR signaling as observed by ZAP-70/LAT activation and Ca2+ influx. Disruption of DIG structure using an agent capable of altering cholesterol organization potently diminished Ca2+ mobilization induced by the coligation of CD3 and CD5. This was associated with the inhibition of the redistribution of DIG although the association of CD3 and CD5 was not affected. Thus, the DIG-resident costimulatory molecules exert their costimulatory effects by contributing to an enhanced association of TCR/CD3 and DIG.

CD5 costimulation up-regulates the signaling to extracellular signal-regulated kinase activation in CD4+CD8+ thymocytes and supports their differentiation to the CD4 lineage

CD5 positively costimulates TCR-stimulated mature T cells, whereas this molecule has been suggested to negatively regulate the activation of TCR-triggered thymocytes. We investigated the effect of CD5 costimulation on the differentiation of CD4+CD8+ thymocytes. Coligation of thymocytes with anti-CD3 and anti-CD5 induced enhanced tyrosine phosphorylation of LAT (linker for activation of T cells) and phospholipase C-gamma (PLC-gamma) compared with ligation with anti-CD3 alone. Despite increased phosphorylation of PLC-gamma, this treatment down-regulated Ca2+ influx. In contrast, the phosphorylation of LAT and enhanced association with Grb2 led to activation of extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase. When CD3 and CD5 on CD4+CD8+ thymocytes in culture were coligated, they lost CD8, down-regulated CD4 expression, and induced CD69 expression, yielding a CD4+(dull)CD8-CD69+ population. An ERK inhibitor, PD98059, inhibited the generation of this population. The reduction of generation of CD4+CD8- cells resulted from decreased survival of these differentiating thymocytes. Consistent with this, PD98059 inhibited the anti-CD3/CD5-mediated Bcl-2 induction. These results indicate that CD5 down-regulates a branch of TCR signaling, whereas this molecule functions to support the differentiation of CD4+CD8+ thymocytes by up-regulating another branch of TCR signaling that leads to ERK activation.

Quantification of ischemic muscle deoxygenation by near infrared time-resolved spectroscopy

The purpose of this study was to quantify muscle deoxygenation in human skeletal muscles using near infrared time-resolved spectroscopy (NIRTRS) and compare NIRTRS indicators and blood saturation. The forearm muscles of five healthy males (aged 27-32 yrs.) were monitored for changes in hemoglobin saturation (SO2) during 12 min of arterial occlusion and recovery. SO2 was determined by measuring the temporal profile of photon diffusion at 780 and 830 nm using NIRTRS, and was defined as SO2-TRS. Venous blood samples were also obtained for measurements of SvO2, and PvO2. Interstitial PO2(PintO2) was monitored by placing an O2 electrode directly into the muscle tissue. Upon the initiation of occlusion, all parameters fell progressively until reaching a plateau in the latter half of occlusion. It was observed at the end of occlusion that SO2-TRS (24.1 +/- 5.6%) agreed with SvO2 (26.2 +/- 6.4) and that PintO2 (14.7 +/- 1.0 Torr) agreed with PvO2 (17.3 +/- 2.2 Torr). The resting O2 store (oxygenated hemoglobin) and O2 consumption rate were 290 microM and 0.82 microM s-1, respectively, values which reasonably agree with the reported results. These results indicate that there was no O2 gradient between vessels and interstisium at the end of occlusion.

Association of a tetraspanin CD9 with CD5 on the T cell surface: role of particular transmembrane domains in the association

CD9 is a member of the tetraspanin superfamily which is characterized by four transmembrane (TM) domains and associates with other surface molecules. This tetraspanin was recently found to be expressed on mature T cells. Here, we investigated which molecules associate with CD9 on T cells and which CD9 domains are required for the association. Immunoprecipitation of T cell lysates with anti-CD9 mAb followed by immunoblotting with mAb against various T cell molecules showed the association of CD9 with CD3, CD4, CD5, CD2, CD29 and CD44. Because association with CD5 was most prominent, we determined the role of CD9 TM or extracellular (EC) domains in the association with CD5. CD9 mutant genes lacking each domain were constructed and introduced into EL4 thymoma cells deficient in CD9 but expressing CD5. Among various types of stable EL4 transfectants, EL4 transfected with the mutant gene lacking TM domains (TM2/TM3) between two EC domains expressed a small amount of the relevant protein without showing association with CD5. CD9(-)CD5(-) monkey COS-7 cells transfected with this mutant gene and the CD5 gene expressed both transfected gene products, but the association of these was not detected. EL4 cells transfected with a CD9/CD81 chimera gene (the CD9 gene containing TM2/TM3 of CD81) expressed the chimeric protein on the cell surface and showed association with CD5. These results suggest an essential role of particular CD9 TM domains in the surface expression of the CD9 molecule as well as the association with CD5.

Guest editorial: special section on medical near-infrared spectroscopy

This Special Section Guest Editorial provides an overview of the topical area and an introduction to the articles featured in the special section.

Translocation of tyrosine-phosphorylated TCRzeta chain to glycolipid-enriched membrane domains upon T cell activation

Recent studies point to glycolipid-enriched membrane (GEM) microdomains as the critical sites for TCR-mediated signal transduction. However, whether the TCR complex is localized in the GEM domain is not well-defined. In the present study, we analyzed localization of the TCR-CD3 complex in the GEM domain by isolating the GEM fraction with sucrose density gradient centrifugation. Although 10% of TCRzeta chains was localized in the GEM fraction, most of the TCR complexes were excluded from the GEM before and after T cell activation, and the amount of TCRzeta in the GEM was not increased after activation. However, the tyrosine-phosphorylated form of TCRzeta was strongly concentrated in the GEM fraction upon TCR engagement. A kinetic study revealed that tyrosine phosphorylation of TCRzeta occurred initially in the Triton X-100-soluble membrane fraction followed by the accumulation of phosphorylated TCRzeta in the GEM. Thus, these results indicate that phosphorylated TCRzeta migrates into the GEM domains on T cell activation. We speculate that the GEM microdomains may function as a reservoir of activation signals from triggered TCR.

A novel vaccine delivery system using immunopotentiating fusogenic liposomes

We previously reported the preparation and characterization of fusogenic liposomes (FLs), which have two highly immunogenic glycoproteins of the Sendai virus on their surface. In this report, we investigated the capacity of FLs to enhance antigen-specific humoral immunity in mice. FLs function as a lymphocyte mitogen with high immunogenicity consistent with viral envelope proteins. Markedly increased levels of anti-ovalbumin (OVA) antibody were detected in serum from mice immunized with OVA encapsulated in FLs compared to sera from mice immunized with free OVA or OVA encapsulated in plain liposomes. An anti-OVA antibody response was not observed in mice immunized with OVA simply mixed with empty FLs. These results indicate that FLs function as a novel immunoadjuvant in inducing antigen-specific antibody production.

Direct suppression of TCR-mediated activation of extracellular signal-regulated kinase by leukocyte protein tyrosine phosphatase, a tyrosine-specific phosphatase

Leukocyte protein tyrosine phosphatase (LC-PTP)/hemopoietic PTP is a human cytoplasmic PTP that is predominantly expressed in the hemopoietic cells. Recently, it was reported that hemopoietic PTP inhibited TCR-mediated signal transduction. However, the precise mechanism of the inhibition was not identified. Here we report that extracellular signal-regulated kinase (ERK) is the direct target of LC-PTP. LC-PTP dephosphorylated ERK2 in vitro. Expression of wild-type LC-PTP in 293T cells suppressed the phosphorylation of ERK2 by a mutant MEK1, which was constitutively active regardless of upstream activation signals. No suppression of the phosphorylation was observed by LC-PTPCS, a catalytically inactive mutant. In Jurkat cells, LC-PTP suppressed the ERK and p38 mitogen-activated protein kinase cascades. LC-PTP and LC-PTPCS made complexes with ERK1, ERK2, and p38alpha, but not with the gain-of-function sevenmaker ERK2 mutant (D321N). A small deletion (aa 1-46) in the N-terminal portion of LC-PTP or Arg to Ala substitutions at aa 41 and 42 resulted in the loss of ERK binding activity. These LC-PTP mutants revealed little inhibition of the ERK cascade activated by TCR cross-linking. On the other hand, the wild-type LC-PTP did not suppress the phosphorylation of sevenmaker ERK2 mutant. Thus, the complex formation of LC-PTP with ERK is the essential mechanism for the suppression. Taken collectively, these results indicate that LC-PTP suppresses mitogen-activated protein kinase directly in vivo.

Regulation of phosphorylation level and distribution of PTP36, a putative protein tyrosine phosphatase, by cell-substrate adhesion

Recently we have cloned a putative protein tyrosine phosphatase, PTP36/PTPD2/pez, which possesses a domain homologous to the N-terminal half of band 4.1 protein. In mouse fibroblasts adhered to substrates, PTP36 was phosphorylated on serine residues. PTP36 was found to make complexes with serine/threonine kinase(s), which phosphorylated PTP36 in vitro. PTP36 was dephosphorylated rapidly when the cell-substrate adhesion was disrupted and it was phosphorylated again along with the reattachment of the cells to fibronectin. Rephosphorylation of PTP36 seemed to depend on actin polymerization since it was inhibited by cytochalasin D. The cell detachment also induced the translocation of PTP36 into the membrane-associated cytoskeletal fraction. Staurosporine and ML-9, which inhibited the phosphorylation of PTP36 in vivo, induced the translocation of PTP36 too. On the contrary, when the dephosphorylation of PTP36 was inhibited by okadaic acid, no translocation of PTP36 was induced by the cell detachment. These results demonstrate that the cell-substrate adhesion and cell spreading regulates the intracellular localization of PTP36 most likely through its phosphorylation and therefore, PTP36 may play important roles in the signal transduction pathway of cell-adhesion.

Pathological and immunological findings of athymic nude and congenic wild type BALB/c mice experimentally infected with Neospora caninum

Neospora is a cyst-forming coccidian parasite that causes abortions and neuromuscular disorders in a wide variety of mammals. Japanese bovine isolate JPA1 was inoculated intraperitoneally into BALB/c nu/ nu (athymic nude) and BALB/c (congenic wild type) female mice to examine the distribution of parasites and resistance mechanisms to Neospora infection. All the athymic nude mice died within 28 days after intraperitoneal injection of 2 x 10(5) JPA1 tachyzoites, whereas all the congenic wild type mice survived without exhibiting any clinical signs. Tachyzoites were identified in the uterus and pancreas and later spread to many other organs. Most tachyzoites identified in the necrotic foci were localized in the epithelium of the venules and capillaries. Nude mice developed high level of serum interferon-gamma and interleukin-6 as infection proceeded. Inflammatory response to Neospora infection might be mediated by Th1-type dependent cellular immunity.

A novel function of Valpha14+CD4+NKT cells: stimulation of IL-12 production by antigen-presenting cells in the innate immune system

The balance between Th1 and Th2 development is determined by IL-4 and IL-12. While the role for CD4+ NK1.1+ T (NKT) cells in influencing this balance has been recognized based on their capacity to produce IL-4, it is unknown how IL-12 is produced in the innate immune system in which they participate. This study demonstrates that Ag-activated CD4+ NKT cells express CD40 ligand (CD40L) (CD154), which engages CD40 on APC and stimulates them to produce IL-12. Culture of B cell-depleted spleen cells from C57BL/6 mice with alpha-galactosylceramide (alpha-GalCer) capable of selectively stimulating Valpha14/Jalpha281+ NKT cells resulted in the production of IL-12 together with IFN-gamma and IL-4. alpha-GalCer-induced IL-12 production occurred in I-Abbeta-deficient mice, but not in beta2-microglobulin-deficient and Valpha14/Jalpha281 TCR-deficient mice, and was inhibited by anti-CD40L mAb. Of CD4+ and CD4- NKT cells, the capacity to express CD40L/CD154 and trigger IL-12 production following alpha-GalCer stimulation was exhibited preferentially by the CD4+ NKT subset. IL-12 production was also observed in alpha-GalCer-treated mice. Production of IL-12 preceded IFN-gamma production, and IL-12 was required for IFN-gamma, but not IL-4, production. A stimulatory/inhibitory relationship existed between IL-12 and IL-4 production. These results illustrate a novel function of CD4+ NKT cells that could be involved in the regulation of Th1 vs Th2 development.

Effects of overexpression of PTP36, a putative protein tyrosine phosphatase, on cell adhesion, cell growth, and cytoskeletons in HeLa cells

Non-receptor-type putative protein tyrosine phosphatase-36 (PTP36), also known as PTPD2/Pez, possesses a domain homologous to the N-terminal half of band 4.1 protein. To gain insight into the biological function of PTP36, we established a HeLa cell line, HtTA/P36-9, in which the overexpression of PTP36 was inducible. PTP36 expressed in HeLa cells was enriched in the cytoskeleton near the plasma membrane. There was little endogenous PTP36 detectable in uninduced HtTA/P36-9 cells or in the parental HeLa cells. Upon induction of PTP36 overexpression, HtTA/P36-9 cells spread less well, grew more slowly, and adhered to the extracellular matrix proteins less well than uninduced cells. Moreover, decreases in the actin stress fibers and the number of focal adhesions were observed. The tyrosine phosphorylation of the focal adhesion kinase induced by lysophosphatidic acid was suppressed in the HtTA/P36-9 cells overexpressing PTP36. These results indicate that PTP36 affects cytoskeletons, cell adhesion, and cell growth, thus suggesting that PTP36 is involved in their regulatory processes.