Plasmacytoid dendritic cells migrate in afferent skin lymph

Bluetongue virus targets conventional dendritic cells in skin lymph

Bluetongue virus (BTV) is the etiological agent of bluetongue, a hemorrhagic disease of ruminants (particularly sheep), which causes important economic losses around the world. BTV is transmitted primarily via the bites of infected midges, which inject the virus into the ruminant's skin during blood feeding. The virus initially replicates in the draining lymph node and then disseminates to secondary organs where it induces edema, hemorrhages, and necrosis. In this study, we show that ovine conventional dendritic cells (cDCs) are the primary targets of BTV that contribute to the primary dissemination of BTV from the skin to draining lymph nodes. Lymph cDCs support BTV RNA and protein synthesis, as well as the production of infectious virus belonging to several different BTV serotypes, regardless of their level of attenuation. Afferent lymph cell subsets, other than cDCs, showed only marginal levels of BTV protein expression. BTV infection provoked a massive recruitment of cDCs to the sheep skin and afferent lymph, providing cellular targets for infection. Although BTV productively infects cDCs, no negative impact on their physiology was detected. Indeed, BTV infection and protein expression in cDCs enhanced their survival rate. Several serotypes of BTV stimulated the surface expression of the CD80 and CD86 costimulatory molecules on cDCs as well as the mRNA synthesis of cytokines involved in inflammation and immunity, i.e., interleukin-12 (IL-12), IL-1beta, and IL-6. BTV-infected cDCs stimulated antigen-specific CD4 and CD8 proliferation as well as gamma interferon production. BTV initially targets cDCs while preserving their functional properties, reflecting the optimal adaptation of the virus to its host cells for its first spread.

The porcine dendritic cell family

Considering the pivotal roles played by dendritic cells (DCs) in both innate and adaptive immune responses, advances in the field of porcine immunology DC biology have recently progressed rapidly. As with the more extensively studied murine and human DCs, porcine DC can be generated from bone marrow haematopoietic cells or monocytes, and have been analysed in various immunological and non-immunological tissues. Both conventional DC (cDC) and plasmacytoid DC (pDC) have been characterized. The function of porcine monocyte-derived DC has not only been characterized in terms of antigen presentation and lymphocyte activation, but also their response to various ligands of pattern recognition receptors. These have been characterized in terms of the induction of DC maturation and pro-inflammatory, Th1-like or Th2-like cytokines secretion. Porcine pDC most effectively sense virus infections and are characterized by their capacity to produce large quantities of IFN-alpha and the pro-inflammatory cytokines TNF-alpha, IL-6 and IL-12. As such, the DC family as a whole is a powerful ally in the host battle against pathogen attack. Nevertheless, DC in particular tissue environments or under particular stimuli can down-regulate immune response development. This is not only important for preventing over-activation of the immune system and also for ensuring tolerance against self or "friendly" substances including food components, but may also be used as a mechanism of pathogens to evade immune responses.

De l’utilité des animaux domestiques pour la recherche en immunologie

Les recherches en immunologie des animaux domestiques fournissent des données complémentaires à celles menées chez la souris, du fait des « opportunités » qu’offrent ces espèces. Certaines d’entre elles font l’objet de cette communication: approche chirurgicale du fonctionnement in vivo des organes lymphoïdes, interventions in utero pour l’étude de l’ontogénèse du système immunitaire, pertinence de l’étude physiopathologique des infections sur espèces cibles.