On-flow magnetic particle activity assay for the screening of human purine nucleoside phosphorylase inhibitors.

Human purine nucleoside phosphorylase (HsPNP) catalyzes reversible phosphorolysis of nucleosides and deoxynucleosides in the purine cascade. HsPNP has been a target on behalf of the development of new leads for the treatment of a variety of T-cell mediated disorders. Several studies on the HsPNP are focused on the identification of effective, safe, and selective inhibitors. Therefore, this study describes the development of direct, simple, reliable, and inexpensive enzymatic assays to screen HsPNP inhibitors. Initially, HsPNP was covalently immobilized on the surface of magnetic particles (MPs). Due to the versatility of the MPs as solid support for enzyme immobilization, two different methods to monitor the enzyme activity are presented. Firstly, the activity of HsPNP-MPs was assessed offline by HPLC-DAD quantifying the formed hypoxanthine. Then, HsPNP-MPs were trapped in a peek tube, furnishing a microreactor which was inserted on-flow in an HPLC-DAD system to monitor the enzyme activity by the hypoxanthine quantification. Kinetic assays provided KMapp values for the inosine substrate of 488.2 ± 49.1 and 1084 ± 111 µM for the offline and on-flow assays, respectively. For the first time, kinetic studies for Pi as substrate using the HsPNP-MPs exhibits a Michaelis-Menten kinetic, yielding KMapp values for offline and on-flow of 521.2 ± 62.9 µM and 601 ± 66.5 µM, respectively. Inhibition studies conducted with a fourth generation immucillin derivative (DI4G) were employed as proof of concept to validate the use of the HsPNP-MPs assays for screening purposes. Additionally, a small library containing 11 compounds was used to assess the selectivity of the developed assays. The results showed that both presented assays can be applied to selectively recognizing and characterizing HsPNP inhibitors. Particularly, the on-flow method exhibited a high throughput and performance because of its automation and represents an easy and practical approach to reuse the HsPNP-MPs. Besides, this novel enzyme activity assay model can be further applied to other biological targets.

Kairomones from Euschistus heros egg masses and their potential use for Telenomus podisi parasitism improvement.

Telenomus podisi Ashmead (Hymenoptera: Scelionidae) is the most important egg parasitoid of Euschistus heros (Fabricius) (Hemiptera: Pentatomidae), and its successful parasitism is related to their searching ability to find suitable hosts under a complex chemical environment using host-reliable cues. Thus, the objective of this study was to elucidate chemical substances on the external layer of E. heros eggs and report its potential kairomonal activity on T. podisi. We tested female wasps in olfactometer system to synthetic compounds obtained from a chemical identification of E. heros egg masses. The synthetic blend was also evaluated in parasitism tests under laboratory and semi-field conditions. We identified 31 substances from egg surface extracts, including monoterpenes, aldehydes and alkanes. Among those compounds, a synthetic solution including camphene, ß-pinene, limonene and benzaldehyde-induced chemotaxic behaviour on the wasps and increased the parasitism on E. heros eggs, either in laboratory or semi-field test, suggesting its potential use to T. podisi manipulation and parasitism improvement.

Male-Produced Sex Pheromone of Tibraca limbativentris Revisited: Absolute Configurations of Zingiberenol Stereoisomers and their Influence on Chemotaxis Behavior of Conspecific Females.

The rice stalk stink bug, Tibraca limbativentris, is an important rice pest in Brazil with a high invasive potential for Mexico and the USA. The sex pheromone of this species was previously identified as a combination of two stereoisomers of 1,10-bisaboladien-3-ol (zingiberenol), but the absolute configurations of these sesquiterpenes were not determined, neither were their effect(s) on T. limbativentris behavior evaluated. In this study, using two chiral columns, we compared retention times of the two natural 1,10-bisaboladien-3-ol stereoisomers from air-entrainment samples of male T. limbativentris with those of synthetic stereoisomers of 1,10-bisaboladien-3-ol. The results showed that T. limbativentris males produce (3S,6S,7R)-1,10-bisaboladien-3-ol (1) and (3R,6S,7R)-1,10-bisaboladien-3-ol (5) as their sex pheromone. Two new minor, male-specific components were also identified as cis and trans isomers of 2,10-bisaboladien-1-ol (sesquipiperitol). Y-tube olfactometer bioassays showed that the major (3S,6S,7R) isomer 1 was essential for attraction of T. limbativentris females, but the minor (3R,6S,7R) isomer 2 was not, nor did it show synergistic/antagonistic effects when added to the major isomer. The (1S,6S,7R) and (1R,6S,7R) stereoisomers of sesquipepiritol also attracted T. limbativentris females.

Age Influence on Sexual Behavior of the Lesser Cornstalk Borer, Elasmopalpus lignosellus (Zeller) (Lepidoptera: Pyralidae).

The objective of this work was to evaluate the reproductive behavior and response of Elasmopalpus lignosellus (Zeller) males to calling females. Frequency of mating was recorded in couples during the first 7 days of the adult stage. Calling behavior of females was observed during the first 4 days of the adult stage and responses of males, in the same age intervals, to calling females were recorded in wind tunnel bioassays. The maximum number of matings occurred when the couple was between 24 and 48 h old. The scotophase period significantly influenced mating behavior, which peaked between 6 and 8 h of darkness and the mean mating duration was 93.9 ± 4.2 min. Calling females, when evaluated in a wind tunnel, attracted significantly more males than in bioassays with clean air (control). The number of individuals in calling behavior was significantly lower for females that were between 0 to 24 h old compared to the other females evaluated, but this did not influence male response. A lower proportion of males between 48 to 72 h old responded to calling females and these responses were delayed in comparison with males of other ages (0 to 24, 24 to 48, and 72 to 96 h old). These results indicate that the age of E. lignosellus males influences the response to conspecific calling females.

Prevalence and Severity of Ratoon Stunt in Commercial Brazilian Sugarcane Fields.

Brazil has 9 million ha of sugarcane, 85% of which are located in the Center-South area of the country. Field trials and surveys around the globe have shown that ratoon stunt disease (RSD), caused by Leifsonia xyli subsp. xyli, can severely reduce tonnage yield. Previous small-scale studies in Brazil have demonstrated RSD infection in all varieties, with values varying from 25 to 68%. Nevertheless, the prevalence and severity of RSD in commercial fields had not previously been assessed. To address this issue, we surveyed 13,173 ha in 1,154 fields of the eight main sugarcane varieties of the Center-South area, taking 92,114 samples from 50 mills in five different states. Our data showed that 10% of fields were infected, and that 58% of mills had at least one RSD-infected field. The variety RB92579 had the highest proportion of infected fields (17%) and, on average, the prevalence and severity in these fields was high compared with other varieties. RB867515, the most cultivated in Brazil, showed infection in 6.2% of sampled fields (5.5% of sampled area) causing an estimated annual economic loss of over US$1 million. This was the first time the economic importance of RSD on Brazilian commercial sugarcane production was estimated. The Cerrado region had the highest prevalence of RSD: 16% of fields, 17% of the cultivated area, and 82% of mills. The use of diseased planting material was identified in 9% of plant cane fields, representing 10% of the cultivated area. Copyright © 2017 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

The influence of volatile semiochemicals from stink bug eggs and oviposition-damaged plants on the foraging behaviour of the egg parasitoid Telenomus podisi.

During host selection, physical and chemical stimuli provide important cues that modify search behaviours of natural enemies. We evaluated the influence of volatiles released by eggs and egg extracts of the stink bug Euschistus heros and by soybean plants treated with the eggs and egg extracts on Telenomus podisi foraging behaviour. Responses to volatiles were evaluated in Y-tube olfactometers after exposure to (1) one egg cluster for 24 h; (2) plants with eggs laid by the stink bug, tested at 24, 48, and 72 h after treatment; (3) plants with eggs laid artificially, tested at 24, 48, and 72 h after treatment; and (4) plants treated with acetone or hexane extracts of eggs. Telenomus podisi was attracted to volatiles emitted by one egg cluster and to acetone extracts of one egg cluster, but not to air or acetone controls. There were no responses to odours of plants treated with eggs or egg extracts. Analysis of acetone extracts of egg clusters by gas chromatography revealed the major components were saturated and unsaturated fatty acids, including hexadecanoic acid, linoleic acid, and (Z)-9-octadecenoic acid. Our results suggest that one egg cluster and the acetone extract of one egg cluster contain volatile compounds that can modify T. podisi foraging behaviour, and that the amounts of these compounds, probably together with some minor compounds, are important for host recognition by T. podisi. Also, the oviposition damage or egg extracts on the plant did not elicit indirect defences that attracted Telenomus podisi.

Chemical Composition of Alphitobius diaperinus (Coleoptera: Tenebrionidae) Abdominal Glands and the Influence of 1,4-benzoquinones on its Behavior.

This study aimed to identify and quantify the compounds present in the abdominal glands of Alphitobius diaperinus Panzer, 1797 (Coleoptera: Tenebrionidae) and to evaluate the influence of these compounds on its behavior. The extraction of volatiles present in the abdominal glands was made by dissection (10 individuals per sex) and by air entrainment (200 insects per sex), and they were analyzed by gas chromatography-flame ionization detector, gas chromatograph-mass spectrometer, and gas chromatograph-electroantennography detector (GC-EAD). The influence of these volatiles on the behavior of conspecifics was evaluated in a four-arm olfactometer. Twenty-three compounds were identified from male and female abdominal gland extracts, of which six were quinones: the 2-methyl-1,4-benzoquinone and the 2-ethyl-1,4-benzoquinone were the major components, and 1,4 benzoquinone and three hydroquinones were registered for the first time for this species. The GC-EAD analysis using the crude extracts from abdominal glands showed that male and female antennae responded to the three major benzoquinones. For the olfactometer bioassays, both genders were repelled either by the abdominal gland extracts or by synthetic solutions containing the three benzoquinones. The results suggest that the 1,4-benzoquinones play a role as a repellent to A. diaperinus.

Herbivory-induced plant volatiles from Oryza sativa and their influence on chemotaxis behaviour of Tibraca limbativentris Stal. (Hemiptera: Pentatomidae) and egg parasitoids.

The rice stem bug, Tibraca limbativentris Stal. (Hemiptera: Pentatomidae) is one of the most important pests of rice crops, especially irrigated crops. Plant defence strategies against these bugs may involve the emission of chemical compounds, which are released following herbivore attacks, directly or indirectly harming pest performance. The aim of this study was to evaluate the influence of constitutive and herbivory-induced volatiles from rice plants (Oryza sativa L.) on the behavioural responses of T. limbativentris adults and egg parasitoids Trissolcus basalis (Wollaston) and Telenomus podisi (Ashmead) (Hymenoptera, Platygastridae). Plant volatiles were collected from undamaged plants of the rice cultivar IRGA 424 and from plants that suffered herbivory by five males or five females of T. limbativentris. Air-entrainment extracts were analysed by GC-flame ionization detector and GC-MS, and insect responses evaluated in a 'Y' olfactometer. T. limbativentris feeding damaged on rice plants induced the release of 16 volatiles compounds in a higher amounts compared to undamaged plants The main compounds induced were (E)-2-hexenal, (E)-2-octen-1-ol, methyl salicylate and α-muurolene. Female bugs were significantly attracted to air-entrainment extracts containing volatiles from undamaged plants compared with air-entrainment extracts containing volatiles emitted from plants damaged by T. limbativentris, whereas males showed no preference. Telenomus podisi females were significantly attracted to volatiles from air-entrainment extracts of plants damaged by females, whereas T. basalis showed no preference. These results suggest that rice plants may be emitting defence compounds, which could be avoided by T. limbativentris females and also acted indirectly by attracting natural enemies.

Identification and Expression Profile of Two Putative Odorant-Binding Proteins from the Neotropical Brown Stink Bug, Euschistus heros (Fabricius) (Hemiptera: Pentatomidae).

This work presents the first identification of putative odorant-binding proteins (OBPs) from a member of the Pentatomidae, i.e. the brown stink bug Euschistus heros (Fabricius), an important pest of soybean in Brazil. Antennae from both sexes of E. heros adults (12 days old and unmated) were used to construct a cDNA library, from which two transcripts encoding putative E. heros OBPs (EherOBPs) were identified. The expression levels of EherOBP1 and EherOBP2 were found to be higher in male antennae than in female and there was difference in expression in legs, wings, and abdomens of the two sexes. The histolocalization of EherOBP1 and EherOBP2 transcripts in antennae also showed a sexual dimorphism in the chemoreception system, with different expression sites in the antennal segments between males and females, occurring predominantly at the base of the sensillum. The implications of these findings for stink bug chemoreception are discussed.

Semiochemicals from herbivory induced cotton plants enhance the foraging behavior of the cotton boll weevil, Anthonomus grandis.

The boll weevil, Anthonomus grandis, has been monitored through deployment of traps baited with aggregation pheromone components. However, field studies have shown that the number of insects caught in these traps is significantly reduced during cotton squaring, suggesting that volatiles produced by plants at this phenological stage may be involved in attraction. Here, we evaluated the chemical profile of volatile organic compounds (VOCs) emitted by undamaged or damaged cotton plants at different phenological stages, under different infestation conditions, and determined the attractiveness of these VOCs to adults of A. grandis. In addition, we investigated whether or not VOCs released by cotton plants enhanced the attractiveness of the aggregation pheromone emitted by male boll weevils. Behavioral responses of A. grandis to VOCs from conspecific-damaged, heterospecific-damaged (Spodoptera frugiperda and Euschistus heros) and undamaged cotton plants, at different phenological stages, were assessed in Y-tube olfactometers. The results showed that volatiles emitted from reproductive cotton plants damaged by conspecifics were attractive to adults boll weevils, whereas volatiles induced by heterospecific herbivores were not as attractive. Additionally, addition of boll weevil-induced volatiles from reproductive cotton plants to aggregation pheromone gave increased attraction, relative to the pheromone alone. The VOC profiles of undamaged and mechanically damaged cotton plants, in both phenological stages, were not different. Chemical analysis showed that cotton plants produced qualitatively similar volatile profiles regardless of damage type, but the quantities produced differed according to the plant's phenological stage and the herbivore species. Notably, vegetative cotton plants released higher amounts of VOCs compared to reproductive plants. At both stages, the highest rate of VOC release was observed in A. grandis-damaged plants. Results show that A. grandis uses conspecific herbivore-induced volatiles in host location, and that homoterpene compounds, such as (E)-4,8-dimethylnona-1,3,7-triene and (E,E)-4,8,12-trimethyltrideca-1,3,7,11-tetraene and the monoterpene (E)-ocimene, may be involved in preference for host plants at the reproductive stage.

Sex pheromone communication in two sympatric neotropical stink bug species Chinavia ubica and Chinavia impicticornis.

Chinavia and Nezara spp. stink bugs (Heteroptera: Pentatomidae) include over100 species, with highest diversity in Afrotropical and Neotropical regions. Species thus far studied in these genera utilize trans-(Z)-(4 S)-bisabolene epoxide (BE) and cis-(Z)-(4 S)-BE as major sex pheromone components, with species specificity ensured by different ratios of the two compounds. Gas chromatography (GC) and coupled GC-mass spectrometry (GC-MS) analyses of a volatiles from C. ubica males revealed the presence of two BE isomers in approximately a 90:10 ratio, which were shown by microprobe (1) H NMR to be cis-(Z)-BE and trans-(Z)-BE isomers, respectively. Analyses of volatiles from C. impicticornis males suggested the presence of a single isomer, trans-(Z)-BE, in high purity (>90 %). The absolute configurations of the isomers produced by C. ubica and C. impicticornis were determined using chiral GC analysis (ß-DEX column). Oxidative microchemistry of synthetic standards of cis-(Z)-(4 S)-BE and trans-(Z)-(4R)-BE, and volatiles from male of C. ubica, revealed the absolute stereochemistry of the cis-(Z)-BE to be (1R,2 S,4 S) [cis-(Z)-(4 S) for short]. Similarly, analyses of trans-(Z)-(4 S)-BE and cis-(Z)-(4R)-BE standards, and volatiles from males of C. ubica and C. impicticornis, revealed the absolute stereochemistry of the trans-(Z)-BE to be (1 S,2R,4 S) [trans-(Z)-(4 S) for short]. Olfactometer bioassays with synthetic BEs confirmed attraction of female C. ubica and C. impicticornis to conspecific synthetic pheromone, but not to heterospecific synthetic pheromone. Chinavia impicticornis appeared not to discriminate behaviorally between the conspecific pheromone and its enantiomer. Coupled GC-electroantennography with antennae from females suggested that C. ubica and C. impicticornis possess olfactory receptors for both cis-(Z)-(4 S)-BE and trans-(Z)-(4 S)-BE. The results in this study confirm that C. ubica and C. impicticornis, as for other Chinavia and Nezara spp., utilize cis-(Z)-(4 S)-BE and trans-(Z)-(4 S)-BE as sex pheromone components, with different ratios guaranteeing species specificity. Furthermore, the results suggest that the absolute stereochemistry of BEs may be less important for conspecific recognition than the relative stereochemistry between the epoxide group and the alkyl substituent on the bisabolene ring.

Percutaneous ultrasound-guided renal biopsy in children - safety, efficacy, indications and renal pathology findings: 14-year Brazilian university hospital experience.

INTRODUCTION: Pediatric percutaneous renal biopsy (Bx) is a routine procedure in pediatric nephrology to obtain renal tissues for histological study. We evaluated the safety, efficacy, indications and renal findings of this procedure at a tertiary care pediatric university hospital and compared our findings with the literature. METHODS: Retrospective study based on medical records from January 1993 to June 2006. RESULTS: In the study period, 305 Bx were performed in 262 patients, 127 (48.5%) male, aged 9.8 A+/- 4.2 years. A 16-gauge needle was utilized in 56/305 Bx, an 18-gauge needle in 252/305 Bx (82.6%). 56.1% Bx were performed under sedation plus local anesthesia, 43.9% under general anesthesia. The number of punctures per Bx was 3.1 A+/- 1.3. Minor complications occurred in 8.6% procedures. The 16-gauge needle caused a higher frequency of renal hematomas (p = 0.05). The number of glomeruli per puncture was >or= 5 in 96.7% and >or= 7 in 92%. Glomeruli number per puncture and frequency of complications were not different according to the type of anesthesia used. A renal pathology diagnosis was achieved in 93.1% Bx. The main indications of Bx were nephrotic syndrome (NS), lupus nephritis (LN) and hematuria (HE). The diagnosis of minimal change disease (MCD) (61.3%), class V (35.6%) and IgA nephropathy (26.3%) predominated in NS, LN and HE patients, respectively. CONCLUSION: Pediatric real-time ultrasound-guided percutaneous renal biopsy was safe and effective. The main clinical indications for Bx were NS and LN, the predominant renal pathology diagnoses were MCD and class V LN.

High-speed countercurrent chromatography as a valuable tool to isolate C-glycosylflavones from Cecropia lyratiloba Miquel.

A new apigeninglycoside, apigenin 6-C-galactosyl-6"-O-beta-galactopyranoside (1), isoorientin, and a mixture of orientin and isovitexin were isolated from leaves of Cecropia lyratiloba by high-speed countercurrent chromatography using a solvent system containing ethyl acetate, butanol, methanol and water. The structural elucidation of 1 was based on NMR spectroscopy.

IL-18 enhances IL-4 production by ligand-activated NKT lymphocytes: a pro-Th2 effect of IL-18 exerted through NKT cells.

NKT cells are a remarkably versatile population whose functional capacities are determined by cytokines present in their microenvironment. In this study, we provide evidence for a new immunoregulatory effect of the proinflammatory cytokine IL-18 on NKT cells. We found that IL-18, mainly known for its involvement in NK cell activation and in Th 1 immune responses, substantially enhanced IL-4 production as well as the percentage of IL-4(+) cells among NKT lymphocytes activated by their specific ligand alpha-galactosylceramide (alpha-GalCer). The effect of IL-18 on IL-4 production by activated NKT cells took place both in vivo and in vitro and was not affected by IL-12 which increased IFN-gamma secretion in the same conditions. We show that NKT cells are the main targets for IL-18-induced IL-4 production since it occurred neither in NKT-deficient mice nor after stimulation of Th2 lymphocytes. Finally, we provide evidence that the IL-4 promptly generated by NKT cells in response to IL-18 plus alpha-galactosylceramide in vivo can effectively contribute to the adaptive Th2 immune response by up-regulating the early activation marker CD69 on B cells. Our data support the notion that, in contrast to the exclusive IFN-gamma inducer IL-12, IL-18 acts in a more subtle manner as a costimulatory factor in both pro-Th1 and pro-Th2 responses depending on the nature of the stimulation and the target cells.

Fas/Fas ligand interactions promote activation-induced cell death of NK T lymphocytes.

NKT cells are a versatile population whose immunoregulatory functions are modulated by their microenvironment. We demonstrate herein that in addition to their IFN-gamma production, NKT lymphocytes stimulated with IL-12 plus IL-18 in vitro underwent activation in terms of CD69 expression, blast transformation, and proliferation. Yet they were unable to survive in culture because, once activated, they were rapidly eliminated by apoptosis, even in the presence of their survival factor IL-7. This process was preceded by up-regulation of Fas (CD95) and Fas ligand expression in response to IL-12 plus IL-18 and was blocked by zVAD, a large spectrum caspase inhibitor, as well as by anti-Fas ligand mAb, suggesting the involvement of the Fas pathway. In accordance with this idea, NKT cells from Fas-deficient C57BL/6-lpr/lpr mice did not die in these conditions, although they shared the same features of cell activation as their wild-type counterpart. Activation-induced cell death occurred also after TCR engagement in vivo, since NKT cells became apoptotic after injection of their cognate ligand, alpha-galactosylceramide, in wild-type, but not in Fas-deficient, mice. Taken together, our data provide the first evidence for a new Fas-dependent mechanism allowing the elimination of TCR-dependent or -independent activated NKT cells, which are potentially dangerous to the organism.

A distinct IL-18-induced pathway to fully activate NK T lymphocytes independently from TCR engagement.

NK T lymphocytes are characterized by their ability to promptly generate IL-4 and IFN-gamma upon TCR engagement. Here, we demonstrate that these cells can also be fully activated in the absence of TCR cross-linking in response to the proinflammatory cytokine IL-18 associated with IL-12. NK T cells stimulated with IL-18 plus IL-12 proliferated, killed Fas+ target cells, and produced high levels of IFN-gamma without IL-4. In these conditions, IFN-gamma production was at least 10-fold higher than that upon TCR cross-linking. Interestingly, a 2-h pretreatment with IL-12 plus IL-18 sufficed to maintain the high IFN-gamma-producing potential during subsequent stimulation with anti-TCR mAbs or with the specific Ag alpha-galactosylceramide. Similar effects were observed in vivo, because splenic CD4+ NK T cells from MHC class II-deficient mice secreted IFN-gamma without further stimulation when removed 2 h after a single injection of IL-12 plus IL-18. In conclusion, our evidence for activation of NK T lymphocytes in response to IL-18 plus IL-12 in the absence of TCR engagement together with the maintenance of preferential IFN-gamma vs IL-4 production upon subsequent exposure to specific Ags is consistent with the active participation of this cell population in innate as well as acquired cellular immune responses.

IL-4-producing NK T cells are biased towards IFN-gamma production by IL-12. Influence of the microenvironment on the functional capacities of NK T cells.

NK T cells are an unusual T lymphocyte subset capable of promptly producing several cytokines after stimulation, in particular IL-4, thus suggesting their influence in Th2 lineage commitment. In this study we demonstrate that, according to the cytokines present in the microenvironment, NK T lymphocytes can preferentially produce either IL-4 or IFN-gamma. In agreement with our previous reports showing that their IL-4-producing capacity is strikingly dependent on IL-7, CD4-CD8-TCRalphabeta+ NK T lymphocytes, obtained after expansion with IL-1 plus granulocyte-macrophage colony-stimulating factor, produced almost undetectable amounts of IL-4 or IFN-gamma in response to TCR/CD3 cross-linking. However, the capacity of these T cells to produce IFN-gamma is strikingly enhanced when IL-12 is added either during their expansion or the anti-CD3 stimulation, while IL-4 secretion is always absent. A similar effect of IL-12 on IFN-gamma production was observed when NK T lymphocytes were obtained after expansion with IL-7. It is noteworthy that whatever cytokines are used for their expansion, IL-12 stimulation, in the absence of TCR/CD3 cross-linking, promotes consistent IFN-gamma secretion by NK T cells without detectable IL-4 production. Experiments in vivo demonstrated a significant upregulation of the capacity of NK T cells to produce IFN-gamma after anti-CD3 mAb injection when mice were previously treated with IL-12. In conclusion, we provide evidence that the functional capacities of NK T cells, which ultimately will determine their physiological roles, are strikingly dependent on the cytokines present in their microenvironment.

Natural killer T cells: a potent cytokine-producing cell population.

Natural killer (NK) T cells constitute a subset of TCRalphabeta+ T lymphocytes characterized by natural killer surface receptor expression as well as by a restricted TCR repertoire. This population is capable both of secreting several cytokines, especially IL-4 and IFN-gamma, shortly after stimulation and of killing target cells via Fas/FasL interactions. The cytokines present in the microenvironment of NK T cells play a pivotal role in their potential immunoregulatory functions which are exerted through their ability to induce apoptosis and to modulate the development of Th1 or Th2 cells. Recent reports concerning the physiological roles of the NK T cell population will be discussed in this review.

Requirement of IL-7 for IL-4-producing potential of MHC class I-selected CD4-CD8-TCR alpha beta+ thymocytes.

IL-7 plays an important role in the growth and differentiation of T cells. We have previously reported that IL-7 induces preferential expansion of MHC class I-selected CD4-CD8-TCR alpha beta+ thymocytes which express a skewed V beta repertoire and are potent IL-4 producers. In this report, we provide evidence that IL-1 in combination with granulocyte macrophage colony stimulating factor can also expand this population. Yet, these cells do not share the functional characteristics of those obtained in the presence of IL-7, i.e. cytotoxic activity and high IL-4 production. These functional capacities can be acquired by adding IL-7. In conclusion, our findings demonstrate that the capacity of MHC class I-selected CD4-CD8-TCR alpha beta+ thymocytes to produce IL-4 as well as to kill target cells is IL-7 dependent.

NK1.1+ T cells from IL-7-deficient mice have a normal distribution and selection but exhibit impaired cytokine production.

Particular subsets of T cells expressing the NK1.1 antigen have been proposed to play an immune regulatory role by their fast and strong production of cytokines, in particular IL-4. We sought to determine factors driving the functional differentiation of NK1.1+ T cells. Since NK1.1+ T cells are exquisitely sensitive to IL-7 stimulation, we analyzed the development, selection and IL-4 production of NK1.1+ T cells in IL-7-deficient mice (IL-7-/-m mice). Besides a sharp reduction of all T cell subsets, NK1.1+ T cells develop at normal relative frequencies in IL-7-/- mice. They also undergo a normal selection process, as revealed by the biased V beta TCR repertoire identical to the one in IL-7+/+ mice. However, NK1.1+ T cells from IL-7-/- mice were found to be impaired in IL-4 and IFN-gamma production in in vitro and in vivo models. In addition, IL-7 was able to restore IL-4 production by NK1.1+ thymocytes from IL-7-/- mice. Finally, IL-7 but not IL-2 or IL-4 was able to maintain and increase IL-4 production by NK1.1+ thymocytes from normal mice. These data suggest that the functional maturation of NK1.1+ T cells requires a cytokine-driven differentiation process, in which IL-7 plays a major role.