Splenic dendritic cells pulsed with Ixodes ricinus tick saliva prime naive CD4+T to induce Th2 cell differentiation in vitro and in vivo

Dendritic cells (DCs) are the most potent antigen-presenting cells (APCs) in priming naive T cells. Using an in vitro priming system, we show that DCs incubated with Ixodes ricinus tick saliva initiate the Th2 differentiation of CD4+T cells. As determined with reverse transcription-PCR, the expression of IL-4 mRNA by these cells is higher than IFN-γ mRNA. Early endogenous production of IL-4 is thought to be important during the in vitro interaction of saliva-pulsed DCs with CD4+T cells. Its neutralization with specific mAbs inhibits the development of IL-4-secreting Th2 cells. Moreover, differentiated Th2 cells proliferate only when saliva-pulsed DCs and IL-1β are added together early in the primary culture. As demonstrated by FACS analysis, the treatment in vitro of saliva-pulsed DCs by IL-1β enhanced the expression of B7 and mainly CD40 co-stimulatory molecules, which provide sufficient signals to stimulate sensitized CD4+T cell proliferation. On the other hand, DCs treated with tick saliva only up-regulated mostly B7-2 co-stimulator expression and this was associated with differentiation of naive CD4+T cells into Th2 type of cells. The in vitro priming system is suitable to investigate the major elements implicated in the anti-tick immune response such as naive CD4+T cells, whole DCs population and tick saliva, and it can provide the possibility to delimit further the saliva molecules, the DC subsets and the type of host cells involved in the Th2 polarization. Corresponding in vivo experiments involving subcutaneous injection of tick saliva-pulsed DCs into BALB/c mice also elicited a Th2 immune response. Ex vivo cultures of draining lymph node T cells stimulated with tick saliva produced higher IL-4 : IFN-γ ratios compared with controls, confirming the relevance obtained in the in vitro priming model. These experiments demonstrate the importance of tick saliva in priming DCs to initiate a Th2-biased immune response in vitro and in viv

Hop-by-Hop Congestion Control for Named Data Network

International audienceNamed Data Networking (NDN) is an Information Centric Networks (ICN) solution that has recently attracted significant attention. NDN changes the Internet communication paradigm from the host-to-host IP model, to a name based communication model. In NDN, the requested Data can be retrieved from different sources and through multiple paths. This distinguished feature of NDN makes the traditional end-to-end congestion control schemes flagging with this new architecture. In this paper, we present a Hop-by-hop congestion control mechanism to regulate the Interest rate between the consumer and the congested router. Each NDN router continuously monitors its outgoing queues occupancy. When the queue size exceeds or falls below a specified threshold, an explicit notification is sent to downstream routers and consumers. The consumer and routers along the path then react by adjusting their Interest sending rates according to the available rate specified in the received notification. We prove the efficiency of the proposed solution and its ability to reduce the congestion impact and to maintain fairness per consumer. We highlight the advantages of our solution using different scenarios implemented in ndnSIM

Par

Modulation de la réponse immunitaire de souris BALB/c infestées par la tique Ixodes ricinus, importance de la salive pour l'induction d'une réponse Th2 in vitr

Impairment of Macrophage Presenting Ability and Viability by Echinococcus granulosus Antigens.

International audienceDespite advances toward an improved understanding of the evasive mechanisms leading to the establishment of cystic echinococcosis, the discovery of specific immunosuppressive mechanisms and related factors are of great interest in the development of an immunotherapeutic approach

Chemical composition, antioxidant and allelopathic activities of essential oils and crude extracts of Cupressus arizonica Greene

Chemical composition, antioxidant, and allelopathic activities of extract from leaves and cones of Tunisian Cupressus arizonica were evaluated. The values of essential oils (EO) yields were 0.18% for leaves and 1.07% for cones. Following GC/MS analysis of C. arizonica leaves and cones, the major compounds identified in leaves EO were umbellulone (19.4%) and α-pinene (10.75%) while the EO of the cones was characterized by its richness with α-pinene (81.3%). In comparison with different extracts, the highest total antioxidant capacity was registered with ethanolic extracts of leaves followed by that of cones. However, the antioxidant activity was stronger with ethanolic extract of leaves than that of cones using both DPPH or ABTS in free radical scavenging activity assays. Results of allelopathic activity showed that the germination reduction depends on the nature of extract and their concentration level. All extracts of C. arizonica decreased the germination of Sinapis arvensis compared to the control. The EO from leaves and cones had the greatest reduction on germination and the strongest growth inhibition followed by the ethanolic extract then the aqueous extract. Results of this study can lead to identification of new phytotoxic compounds in extracts of C. arizonica useful in controlling weeds.La composition chimique, les activités antioxydantes et allélopathiques de l’extrait de feuilles et de cônes de Cupressus arizonica de Tunisie ont été évaluées. Les valeurs des rendements en huiles essentielles (HE) étaient de 0,18 % pour les feuilles et de 1,07 % pour les cônes. Grâce à l’analyse par GC/MS des feuilles et des cônes de C. arizonica, les principaux composés identifiés dans l’HE des feuilles étaient l’umbellulone (19,4 %) et l’α-pinène (10,75 %) tandis que l’HE des cônes était caractérisée par sa richesse en α-pinène (81,3 %). Par rapport à différents extraits, la capacité antioxydante totale la plus élevée a été enregistrée avec les extraits éthanoliques des feuilles, suivie par celle des cônes. Cependant, l’activité antioxydante était plus forte avec l’extrait éthanolique des feuilles que celle des cônes en utilisant DPPH ou ABTS dans les deux tests d’activité de piégeage des radicaux libres. Les résultats de l’activité allélopathique ont montré que la réduction de la germination dépend de la nature des extraits et de leurs niveaux de concentration. Tous les extraits de C. arizonica étaient capables de diminuer la germination de Sinapis arvensis par rapport au témoin. Les HE des feuilles et des cônes avaient un impact plus important sur la réduction de la germination et l’inhibition de la croissance, suivi par l’extrait éthanolique puis par l’extrait aqueux. Les résultats de cette étude peuvent conduire à identifier de nouveaux composés phytotoxiques dans des extraits de C. arizonica utiles pour la lutte contre les mauvaises herbes