Protease-activated receptor 2 signalling promotes dendritic cell antigen transport and T-cell activation in vivo.

Deficiency of protease-activated receptor-2 (PAR2) modulates inflammation in several models of inflammatory and autoimmune disease, although the underlying mechanism(s) are not understood. PAR2 is expressed on endothelial and immune cells, and is implicated in dendritic cell (DC) differentiation. We investigated in vivo the impact of PAR2 activation on DCs and T cells in PAR2 wild-type (WT) and knockout (KO) mice using a specific PAR2 agonist peptide (AP2). PAR2 activation significantly increased the frequency of mature CD11c(high) DCs in draining lymph nodes 24 hr after AP2 administration. Furthermore, these DCs exhibited increased expression of major histocompatibility complex (MHC) class II and CD86. A significant increase in activated (CD44(+) CD62(-)) CD4(+) and CD8(+) T-cell frequencies was also observed in draining lymph nodes 48 hr after AP2 injection. No detectable change in DC or T-cell activation profiles was observed in the spleen. The influence of PAR2 signalling on antigen transport to draining lymph nodes was assessed in the context of delayed-type hypersensitivity. PAR2 WT mice that were sensitized by skin-painting with fluorescein isothiocyanate (FITC) to induce delayed-type hypersensitivity possessed elevated proportion of FITC(+) DCs in draining lymph nodes 24 hr after FITC painting when compared with PAR2 KO mice (0.95% versus 0.47% of total lymph node cells). Collectively, these results demonstrate that PAR2 signalling promotes DC trafficking to the lymph nodes and subsequent T-cell activation, and thus provides an explanation for the pro-inflammatory effect of PAR2 in animal models of inflammation.

Human invariant V alpha 24-J alpha Q TCR supports the development of CD1d-dependent NK1.1+ and NK1.1- T cells in transgenic mice.

A sizable fraction of T cells expressing the NK cell marker NK1.1 (NKT cells) bear a very conserved TCR, characterized by homologous invariant (inv.) TCR V alpha 24-J alpha Q and V alpha 14-J alpha 18 rearrangements in humans and mice, respectively, and are thus defined as inv. NKT cells. Because human inv. NKT cells recognize mouse CD1d in vitro, we wondered whether a human inv. V alpha 24 TCR could be selected in vivo by mouse ligands presented by CD1d, thereby supporting the development of inv. NKT cells in mice. Therefore, we generated transgenic (Tg) mice expressing the human inv. V alpha 24-J alpha Q TCR chain in all T cells. The expression of the human inv. V alpha 24 TCR in TCR C alpha(-/-) mice indeed rescues the development of inv. NKT cells, which home preferentially to the liver and respond to the CD1d-restricted ligand alpha-galactosylceramide (alpha-GalCer). However, unlike inv. NKT cells from non-Tg mice, the majority of NKT cells in V alpha 24 Tg mice display a double-negative phenotype, as well as a significant increase in TCR V beta 7 and a corresponding decrease in TCR V beta 8.2 use. Despite the forced expression of the human CD1d-restricted TCR in C alpha(-/-) mice, staining with mCD1d-alpha-GalCer tetramers reveals that the absolute numbers of peripheral CD1d-dependent T lymphocytes increase at most by 2-fold. This increase is accounted for mainly by an increased fraction of NK1.1(-) T cells that bind CD1d-alpha-GalCer tetramers. These findings indicate that human inv. V alpha 24 TCR supports the development of CD1d-dependent lymphocytes in mice, and argue for a tight homeostatic control on the total number of inv. NKT cells. Thus, human inv. V alpha 24 TCR-expressing mice are a valuable model to study different aspects of the inv. NKT cell subset.

The changing preference of T and B cells for partners as T-dependent antibody responses develop.

Recirculating virgin CD4+ T cells spend their life migrating between the T zones of secondary lymphoid tissues where they screen the surface of interdigitating dendritic cells. T-cell priming starts when processed peptides or superantigen associated with class II MHC molecules are recognised. Those primed T cells that remain within the lymphoid tissue move to the outer T zone, where they interact with B cells that have taken up and processed antigen. Cognate interaction between these cells initiates immunoglobulin (Ig) class switch-recombination and proliferation of both B and T cells; much of this growth occurs outside the T zones B cells migrate to follicles, where they form germinal centres, and to extrafollicular sites of B-cell growth, where they differentiate into mainly short-lived plasma cells. T cells do not move to the extrafollicular foci, but to the follicles; there they proliferate and are subsequently involved in the selection of B cells that have mutated their Ig variable-region genes. During primary antibody responses T-cell proliferation in follicles produces many times the peak number of T cells found in that site: a substantial proportion of the CD4+ memory T-cell pool may originate from growth in follicles.

New insights into the long-term evolutionary history of the avian MHC

SummaryGene duplication and neofunctidnalization are important processes in the evolution of phenotypic complexity. They account for important evolutionary novelties that confer ecological adaptation, such as the major histocompatibility complex (MHC), a multigene family with a central role in vertebrates' adaptive immune system. Multigene families, which evolved in large part through duplication, represent promising systems to study the still strongly depbated relative roles of neutral and adaptive processes in the evolution of phenotypic complexity. Detailed knowledge on ecological function and a well-characterized evolutionary history place the mammals' MHC amongst ideal study systems. However mammalian MHCs usually encompass several million base pairs and hold a large number of functional and non-functional duplicate genes, which makes their study complex. Avian MHCs on the other hand are usually way more compact, but the reconstruction of. their evolutionary history has proven notoriously difficult. However, no focused attempt has been undertaken so far to study the avian MHC evolutionary history in a broad phylogenetic context and using adequate gene regions.In the present PhD, we were able to make important contributions to the understanding of the long-term evolution of the avian MHC class II Β (MHCI1B). First, we isolated and characterized MHCIIB genes in barn owl (Tyto alba?, Strigiformes, Tytonidae), a species from an avian lineage in which MHC has not been studied so far. Our results revealed that with only two functional MHCIIB genes the MHC organization of barn owl may be similar to the 'minimal essential' MHC of chicken (Gallus gallus), indicating that simple MHC organization may be ancestral to birds. Taking advantage of the sequence information from barn owl, we studied the evolution of MHCIIB genes in 13 additional species of 'typical' owls (Strigiformes, Strigidae). Phylogenetic analyses revealed that according to their function, in owls the peptide-binding region (PBR) encoding exon 2 and the non-PBR encoding exon 3 evolve by different patterns. Exon 2 exhibited an evolutionary history of positive selection and recombination, while exon 3 traced duplication history and revealed two paralogs evolving divergently from each other in owls, and in a shorebird, the great snipe {Gallinago media). The results from exon 3 were the first ever from birds to demonstrate gene orthology in species that diverged tens of millions of years ago, and strongly questioned whether the taxa studied before provided an adequate picture of avian MHC evolution. In a follow-up study, we aimed at explaining a striking pattern revealed by phylogenetic trees analyzing the owl sequences along with MHCIIB sequences from other birds: One owl paralog (termed DAB1) grouped with sequences of passerines and falcons, while the other (DAB2) grouped with wildfowl, penguins and birds of prey. This could be explained by either a duplication event preceding the evolution of these bird orders, or by convergent evolution of similar sequences in a number of orders. With extensive phylogenetic analyses we were able to show, that indeed a duplication event preceeded the major avian radiation -100 my ago, and that following this duplication, the paralogs evolved under positive selection. Furthermore, we showed that the divergently evolving amino acid residues in the MHCIIB-encoded β-chain potentially interact with the MHCI I α-chain, and that molecular coevolution of the interacting residues may have been involved in the divergent evolution of the MHCIIB paralogs.The findings of this PhD are of particular interest to the understanding of the evolutionary history of the avian MHC and, by providing essential information on long-term gene history in the avian MHC, open promising perspectives for advances in the understanding of the evolution of multigene families in general, and for avian MHC organization in particular. Amongst others I discuss the importance of including protein structure in the phylogenetic study of multigene families, and the roles of ecological versus molecular selection pressures. I conclude by providing a population genomic perspective on avian MHC, which may serve as a basis for future research to investigate the relative roles of neutral processes involving effective population size effects and of adaptation in the evolution of avian MHC diversity and organization.RésuméLa duplication de gènes et leur néo-fonctionnalisation sont des processus importants dans l'évolution de la complexité phénotypique. Ils sont impliqués dans l'apparition d'importantes nouveautés évolutives favorisant l'adaptation écologique, comme c'est le cas pour le complexe majeur d'histocompatibilité classe II Β (CMH II Β). Nous avons isolé et caractérisé les gènes CMH I IB de la chouette effraie (Tyto alba; Strigiformes, Tytonidae), une espèce appartenant à une lignée aviaire dont le CMH n'avait pas été étudié jusqu'ici. Avec uniquement deux gènes CMHIIB fonctionnels, l'organisation CMH de la chouette effraie semble être comparable à celle "minimale" du poulet (Gallus gallus), ce qui suggère qu'une organisation simple du CMH pourrait être ancestrale chez les oiseaux. En se basant sur l'information obtenue pour cette espèce, nous avons ensuite étudié l'évolution des gènes CMHIIB chez 13 espèces de chouettes "typiques" (Strigiformes, Strigidae). Les analyses phylogénétiques ont révélé que chez les chouettes, selon leur fonction, l'exon 2 codant pour la 'peptide-binding region' (PBR) et l'exon 3 ne codant pas pour la région PBR évoluent de manière distincte. L'exon 2 montre une histoire évolutive de sélection positive et recombinaison, tandis que l'exon 3 retrace l'histoire de duplication et révèle deux paralogues évoluant de façon divergente chez les chouettes, ainsi que chez un limicole, la bécassine double (Gallinago media). Les résultats découlant de l'analyse de l'exon 3 ont montré pour la première fois chez les oiseaux une orthologie de gènes chez des espèces ayant divergé il y a des dizaines de millions d'années. Dans une deuxième étude, nous avons voulu expliquer le pattern surprenant révélé par les arbres phylogénétiques lorsque les séquences CMHIIB des chouettes sont analysées avec les séquences d'autres oiseaux: un paralogue de chouette (appelé DABI) forme un groupe avec les séquences de passereaux et faucons, tandis que l'autre (DAB2) se regroupe avec les gallo-ansériformes, les manchots et les rapaces diurnes. Ceci pourrait être expliqué soit par une duplication qui a précédé l'évolution de ces ordres aviaires soit par évolution convergente dans un certain nombre d'ordres. Grâce à des analyses phylogénétiques approfondies, nous avons pu montrer qu'un événement de duplication a effectivement précédé la radiation aviaire principale d'il y a environ 100 millions d'années, et qu'après cette duplication les paralogues ont évolué sous sélection positive. De plus, les résidus d'acides aminés évoluant de façon divergente dans la chaîne β codée par le CMHIIB interagissent potentiellement avec la chaîne α codée par le CMHII, et que la coévolution moléculaire de ces résidus pourrait être à la base de l'évolution divergente des paralogues CMHIIB.Dans cette thèse sont discutés entre autres l'importance d'inclure la structure des protéines dans l'étude phylogénétique des familles multigéniques, ainsi que les rôles respectifs des pressions sélectives écologique et moléculaire. La conclusion comporte une perspective sur la génomique des populations du CMH aviaire, qui pourrait servir de base pour de futures recherches sur les rôles relatifs joués par Îes processus neutres comprenant les effets de la taille efficace des populations et l'adaptation dans l'évolution de la diversité et l'organisation du MHC aviaire.

Effect of acute and chronic exercise on fat oxidation and hormonal and plasma metabolite kinetics in obese and severely obese men

Acute exercise increases energy expenditure (EE) during exercise and post-exercise recovery [excess post-exercise oxygen consumption (EPOC)] and therefore may be recommended as part of the multidisciplinary management of obesity. Moreover, chronic exercise (training) effectively promotes an increase in insulin sensitivity, which seems to be associated with increased fat oxidation rates (FORs). The main purpose of this thesis is to investigate 1) FORs and extra-muscular factors (hormones and plasma metabolites) that regulate fat metabolism during acute and chronic exercise; and 2) EPOC during acute post-exercise recovery in obese and severely obese men (class II and III). In the first study, we showed that obese and severely obese men present a lower exercise intensity (Fatmax) eliciting maximal fat oxidation and a lower reliance on fat oxidation at high, but not at low and moderate, exercise intensities compared to lean men. This was most likely related to an impaired muscular capacity to oxidize non-esterified fatty acids (NEFA) rather than decreased plasma NEFA availability or a change in the hormonal milieu during exercise. In the second study, we developed an accurate maximal incremental test to correctly and simultaneously evaluate aerobic fitness and fat oxidation kinetics during exercise in this population. This test may be used for the prescription of an appropriate exercise training intensity. In the third study, we demonstrated that only 2 wk of exercise training [continuous training at Fatmax and adapted high-intensity interval training (HIIT)], matched with respect to mechanical work, may be effective to improve aerobic fitness, FORs during exercise and insulin sensitivity, which suggest that FORs might be rapidly improved and that adapted HIIT is feasible in this population. The increased FORs concomitant with the lack of changes in lipolysis during exercise suggest an improvement in the mismatching between NEFA availability and oxidation, highlighting the importance of muscular (oxidative capacity) rather than extra-muscular (hormones and plasma metabolites) factors in the regulation of fat metabolism after a training program. In the fourth study, we observed a positive correlation between EE during exercise and EPOC, suggesting that a chronic increase in the volume or intensity of exercise may increase EE during exercise and during recovery. This may have an impact in weight management in obesity. In conclusion, these findings might have practical implications for exercise training prescriptions in order to improve the therapeutic approaches in obesity and severe obesity. -- L'exercice aigu augmente la dépense énergétique (DE) pendant l'exercice et la récupération post-exercice [excès de consommation d'oxygène post-exercise (EPOC)] et peut être utilisé dans la gestion multidisciplinaire de l'obésité. Quant à l'exercice chronique (entraînement), il est efficace pour augmenter la sensibilité à l'insuline, ce qui semble être associé à une amélioration du débit d'oxydation lipidique (DOL). Le but de cette thèse est d'étudier 1) le DOL et les facteurs extra-musculaires (hormones et métabolites plasmatiques) qui régulent le métabolisme lipidique pendant l'exercice aigu et chronique et 2) l'EPOC lors de la récupération aiguë post-exercice chez des hommes obèses et sévèrement obèses (classe II et III). Dans la première étude nous avons montré que les hommes obèses et sévèrement obèses présentent une plus basse intensité d'exercice (Fatmax) correspondant au débit d'oxydation lipidique maximale et un plus bas DOL à hautes, mais pas à faibles et modérées, intensités d'exercice comparé aux sujets normo-poids, ce qui est probablement lié à une incapacité musculaire à oxyder les acides gras non-estérifiés (AGNE) plutôt qu'à une diminution de leur disponibilité ou à un changement du milieu hormonal pendant l'exercice. Dans la deuxième étude nous avons développé un test maximal incrémental pour évaluer simultanément l'aptitude physique aérobie et la cinétique d'oxydation des lipides pendant l'exercice chez cette population. Dans la troisième étude nous avons montré que seulement deux semaines d'entraînement (continu à Fatmax et intermittent à haute intensité), appariés par la charge de travail, sont efficaces pour améliorer l'aptitude physique aérobie, le DOL pendant l'exercice et la sensibilité à l'insuline, ce qui suggère que le DOL peut être rapidement amélioré chez cette population. Ceci, en absence de changements de la lipolyse pendant l'exercice, suggère une amélioration de la balance entre la disponibilité et l'oxydation des AGNE, ce qui souligne l'importance des facteurs musculaires (capacité oxydative) plutôt que extra-musculaires (hormones et métabolites plasmatiques) dans la régulation du métabolisme lipidique après un entraînement. Dans la quatrième étude nous avons observé une corrélation positive entre la DE pendant l'exercice et l'EPOC, ce qui suggère qu'une augmentation chronique du volume ou de l'intensité de l'exercice pourrait augmenter la DE lors de l'exercice et lors de la récupération post-exercice. Ceci pourrait avoir un impact sur la gestion du poids chez cette population. En conclusion, ces résultats pourraient avoir des implications pratiques lors de la prescription des entraînements dans le but d'améliorer les approches thérapeutiques de l'obésité et de l'obésité sévère.

Extensive variation at MHC DRB in the New Zealand sea lion (Phocarctos hookeri) provides evidence for balancing selection.

Marine mammals are often reported to possess reduced variation of major histocompatibility complex (MHC) genes compared with their terrestrial counterparts. We evaluated diversity at two MHC class II B genes, DQB and DRB, in the New Zealand sea lion (Phocarctos hookeri, NZSL) a species that has suffered high mortality owing to bacterial epizootics, using Sanger sequencing and haplotype reconstruction, together with next-generation sequencing. Despite this species' prolonged history of small population size and highly restricted distribution, we demonstrate extensive diversity at MHC DRB with 26 alleles, whereas MHC DQB is dimorphic. We identify four DRB codons, predicted to be involved in antigen binding, that are evolving under adaptive evolution. Our data suggest diversity at DRB may be maintained by balancing selection, consistent with the role of this locus as an antigen-binding region and the species' recent history of mass mortality during a series of bacterial epizootics. Phylogenetic analyses of DQB and DRB sequences from pinnipeds and other carnivores revealed significant allelic diversity, but little phylogenetic depth or structure among pinniped alleles; thus, we could neither confirm nor refute the possibility of trans-species polymorphism in this group. The phylogenetic pattern observed however, suggests some significant evolutionary constraint on these loci in the recent past, with the pattern consistent with that expected following an epizootic event. These data may help further elucidate some of the genetic factors underlying the unusually high susceptibility to bacterial infection of the threatened NZSL, and help us to better understand the extent and pattern of MHC diversity in pinnipeds.

Identification of key amino acids of the mouse mammary tumor virus superantigen involved in the specific interaction with T-cell receptor V(beta) domains.

Mouse mammary tumor virus (MMTV) is a retrovirus encoding a superantigen that is recognized in association with major histocompatibility complex class II by the variable region of the beta chain (V(beta)) of the T-cell receptor. The C-terminal 30 to 40 amino acids of the superantigen of different MMTVs display high sequence variability that correlates with the recognition of particular T-cell receptor V(beta) chains. Interestingly, MMTV(SIM) and mtv-8 superantigens are highly homologous but have nonoverlapping T-cell receptor V(beta) specificities. To determine the importance of these few differences for specific V(beta) interaction, we studied superantigen responses in mice to chimeric and mutant MMTV(SIM) and mtv-8 superantigens expressed by recombinant vaccinia viruses. We show that only a few changes (two to six residues) within the C terminus are necessary to modify superantigen recognition by specific V(beta)s. Thus, the introduction of the MMTV(SIM) residues 314-315 into the mtv-8 superantigen greatly decreased its V(beta)12 reactivity without gain of MMTV(SIM)-specific function. The introduction of MMTV(SIM)-specific residues 289 to 295, however, induced a recognition pattern that was a mixture of MMTV(SIM)- and mtv-8-specific V(beta) reactivities: both weak MMTV(SIM)-specific V(beta)4 and full mtv-8-specific V(beta)11 recognition were observed while V(beta)12 interaction was lost. The combination of the two MMTV(SIM)-specific regions in the mtv-8 superantigen established normal MMTV(SIM)-specific V(beta)4 reactivity and completely abolished mtv-8-specific V(beta)5, -11, and -12 interactions. These new functional superantigens with mixed V(beta) recognition patterns allowed us to precisely delineate sites relevant for molecular interactions between the SIM or mtv-8 superantigen and the T-cell receptor V(beta) domain within the 30 C-terminal residues of the viral superantigen.

The orphan receptor CRF2-4 is an essential subunit of the interleukin 10 receptor.

The orphan receptor CRF2-4 is a member of the class II cytokine receptor family (CRF2), which includes the interferon receptors, the interleukin (IL) 10 receptor, and tissue factor. CRFB4, the gene encoding CRF2-4, is located within a gene cluster on human chromosome 21 that comprises three interferon receptor subunits. To elucidate the role of CRF2-4, we disrupted the CRFB4 gene in mice by means of homologous recombination. Mice lacking CRF2-4 show no overt abnormalities, grow normally, and are fertile. CRF2-4 deficient cells are normally responsive to type I and type II interferons, but lack responsiveness to IL-10. By approximately 12 wk of age, the majority of mutant mice raised in a conventional facility developed a chronic colitis and splenomegaly. Thus, CRFB4 mutant mice recapitulate the phenotype of IL-10-deficient mice. These findings suggest that CRF2-4 is essential for IL-10-mediated effects and is a subunit of the IL-10 receptor.

Evaluation of melanoma vaccines with molecularly defined antigens by ex vivo monitoring of tumor-specific T cells.

Immunotherapy of melanoma is aimed to mobilize cytolytic CD8+ T cells playing a central role in protective immunity. Despite numerous clinical vaccine trials, only few patients exhibited strong antigen-specific T-cell activation, stressing the need to improve vaccine strategies. For a rational development, we propose to focus on molecularly defined vaccine components, and evaluate their immunogenicity with highly reproducible and standardized methods for ex vivo immune monitoring. Careful immunogenicity comparison of vaccine formulations in phase I/II studies allow to select optimized vaccines for subsequent clinical efficacy testing in large scale phase III trials.

The human Ia-associated invariant chain is synthesized in Ia-negative B cell variants and is not expressed on the cell surface of both Ia-negative and Ia-positive parental cells.

The expression of Ia-associated human Invariant (In) chain glycoproteins was studied in the Raji B cells as well as in their RJ 2.2.5 Ia-negative derived variant cells by using a specific rabbit anti-human In chain antiserum. Two-dimensional gel electrophoresis of immunoprecipitates from either biosynthetically labeled or surface labeled cells were analyzed. In addition, flow microfluorometric analysis of stained cells was performed. The results indicate that the In chain is constitutively produced in the Ia-negative B cell variant. Moreover, it appears that several forms of In chain-related molecules, with different charges and distinct m.w. are equally expressed in Ia-positive and Ia-negative B cells. Finally, no evidence could be obtained that the In molecular family was expressed on the cell surface of Ia-positive Raji and Ia-negative RJ 2.2.5 cells.

BAFF production by antigen-presenting cells provides T cell co-stimulation.

The B cell-activating factor from the tumor necrosis factor family (BAFF) is an important regulator of B cell immunity. Recently, we demonstrated that recombinant BAFF also provides a co-stimulatory signal to T cells. Here, we studied expression of BAFF in peripheral blood leukocytes and correlated this expression with BAFF T cell co-stimulatory function. BAFF is produced by antigen-presenting cells (APC). Blood dendritic cells (DC) as well as DC differentiated in vitro from monocytes or CD34+ stem cells express BAFF mRNA. Exposure to bacterial products further up-regulates BAFF production in these cells. A low level of BAFF transcription, up-regulated upon TCR stimulation, was also detected in T cells. Functionally, blockade of endogenous BAFF produced by APC and, to a lesser extent, by T cells inhibits T cell activation. Altogether, this indicates that BAFF may regulate T cell immunity during APC-T cell interactions and as an autocrine factor once T cells have detached from the APC.

Cyclic AMP induces differentiation in vitro of human melanoma cells.

Treating human melanoma lines with dibutyryl adenosine 3':5'-cyclic monophosphate (dbc AMP) resulted in morphologic changes associated with the altered expression of cell surface antigens. After treatment, cells developed long cellular projections characteristic of mature melanocytes and showed the presence of an increased number of Stage II premelanosomes. In addition, induction of melanin synthesis, detected as brown perinuclear pigmentation, was observed. The AMP further drastically reduced the growth rate of the five melanoma cell lines that were tested. The influence of dbc AMP was completely reversible 3 days after the agent was removed from the culture medium. The antigenic phenotype of the melanoma lines was compared before and after dbc AMP treatment. This was done with four monoclonal antibodies directed against major histocompatibility complex (MHC) Class I and II antigens and 11 monoclonal antibodies defining eight different melanoma-associated antigenic systems. Treatment with dbc AMP reduced the expression of human leukocyte antigen (HLA)-ABC antigens and beta-2-microglobulin in five of five melanoma lines. In the two HLA-DR-positive cell lines dbc AMP reduced the expression of this antigen in one line and enhanced it in the other. No induction of HLA-DR or HLA-DC antigens was observed in the Class II negative cell lines. Furthermore, dbc-AMP modulated the expression of the majority of the melanoma antigenic systems tested. The expression of a 90-kilodalton (KD) antigen, which has been found to be upregulated by interferon-gamma, was markedly decreased in all the five cell lines. A similar decrease in the expression of the high molecular weight proteoglycan-associated antigen (220-240 KD) was observed. The reduced expression of Class I and II MHC antigens as well as the altered expression of the melanoma-associated antigens studied were shown to be reversible after dbc AMP was removed. Our results collectively show that the monoclonal antibody-defined melanoma-associated molecules are linked to differentiation. They could provide useful tools for monitoring the maturation of melanomas in vivo induced by chemical agents or natural components favoring differentiation.

A comparative study of T-cell receptor V beta usage in non-obese diabetic (NOD) and I-E transgenic NOD mice.

The non-obese diabetic (NOD) mouse is a model for the study of insulin-dependent diabetes mellitus (IDDM). Recently transgenic NOD mice have been derived (NOD-E) that express the major histocompatibility complex (MHC) class II I-E molecule. NOD-E do not become diabetic and show negligible pancreatic insulitis. The possibility pertained that NOD-E mice are protected from disease by a process of T-cell deletion or anergy. This paper describes our attempts to discover whether this was so, by comparing NOD and NOD-E mouse T-cell receptor V beta usage. Splenocytes and lymph node cells were therefore tested for their ability to proliferate in response to monoclonal anti-V beta antibodies. We were unable to show any consistent differences between NOD and NOD-E responses to the panel of antibodies used. Previously proposed V beta were shown to be unlikely candidates for deletion or anergy. T cells present at low frequency (V beta 5+) in both NOD and NOD-E mice were shown to be as capable of expansion in response to antigenic stimulation as were more frequently expressed V beta. Our data therefore do not support deletion or anergy as mechanisms which could account for the observed disease protection in NOD-E mice.

Acute coronary syndromes in young patients: presentation, treatment and outcome.

BACKGROUND: Acute coronary syndromes (ACS) in very young patients have been poorly described. We therefore evaluate ACS in patients aged 35 years and younger. METHODS: In this prospective cohort study, 76 hospitals treating ACS in Switzerland enrolled 28,778 patients with ACS between January 1, 1997, and October 1, 2008. ACS definition included ST-segment elevation myocardial infarction (STEMI), non-ST-segment elevation myocardial infarction (NSTEMI), and unstable angina (UA). RESULTS: 195 patients (0.7%) were 35 years old or younger. Compared to patients>35 years, these patients were more likely to present with chest pain (91.6% vs. 83.7%; P=0.003) and less likely to have heart failure (Killip class II to IV in 5.2% vs. 23.0%; P<0.001). STEMI was more prevalent in younger than in older patients (73.1% vs. 58.3%; P<0.001). Smoking, family history of CAD, and/or dyslipidemia were important cardiovascular risk factors in young patients (prevalence 77.2%, 55.0%, and 44.0%). The prevalence of overweight among young patients with ACS was high (57.8%). Cocaine abuse was associated with ACS in some young patients. Compared to older patients, young patients were more likely to receive early percutaneous coronary interventions and had better outcome with fewer major adverse cardiac events. CONCLUSIONS: Young patients with ACS differed from older patients in that the younger often presented with STEMI, received early aggressive treatment, and had favourable outcomes. Primary prevention of smoking, dyslipidemia and overweight should be more aggressively promoted in adolescence.