MHC class II–restricted antigen presentation by plasmacytoid dendritic cells inhibits T cell–mediated autoimmunity

Although plasmacytoid dendritic cells (pDCs) express major histocompatibility complex class II (MHCII) molecules, and can capture, process, and present antigens (Ags), direct demonstrations that they function as professional Ag-presenting cells (APCs) in vivo during ongoing immune responses remain lacking. We demonstrate that mice exhibiting a selective abrogation of MHCII expression by pDCs develop exacerbated experimental autoimmune encephalomyelitis (EAE) as a consequence of enhanced priming of encephalitogenic CD4+ T cell responses in secondary lymphoid tissues. After EAE induction, pDCs are recruited to lymph nodes and establish MHCII-dependent myelin-Ag–specific contacts with CD4+ T cells. These interactions promote the selective expansion of myelin-Ag–specific natural regulatory T cells that dampen the autoimmune T cell response. pDCs thus function as APCs during the course of EAE and confer a natural protection against autoimmune disease development that is mediated directly by their ability to present of Ags to CD4+ T cells in vivo

Dissecting IL-6 responses in inflammation

L'Interleukin-6 (IL-6) joue un rôle primordial dans le développement de réponses immunitaires locales (exemple: inflammation au niveau des tissus synoviaux) et dans la coordination des réponses immunitaires systémiques (exemple: induction de la sécrétion d'anticorps par les cellules B activées et différenciées, ou induction de la sécrétion de protéines de la phase aïgue par les hépatocytes). Cependant, la contribution relative des deux voies de signalisation activées par l'IL-6 (voie cis et voie trans) dans le développement d'une réponse immunitaire locale et systémique reste à déterminer. Buts de la thèse : - Explorer les rôles respectifs des voies de cis-signalisation et de trans-signalisation dans le développement d'une réponse inflammatoire. Afin de définir les rôles respectifs des voies cis et trans lors d'une réponse inflammatoire locale et systémique, nous avons : - Généré des anticorps monoclonaux ciblant de différentes manières les 2 voies de signalisation activées par l'IL-6. - Utilisé ces anticorps in vivo dans deux modèles murins d'inflammation

Rapid, simple and high yield production of recombinant proteins in mammalian cells using a versatile episomal system.

Many research projects in life sciences require purified biologically active recombinant protein. In addition, different formats of a given protein may be needed at different steps of experimental studies. Thus, the number of protein variants to be expressed and purified in short periods of time can expand very quickly. We have therefore developed a rapid and flexible expression system based on described episomal vector replication to generate semi-stable cell pools that secrete recombinant proteins. We cultured these pools in serum-containing medium to avoid time-consuming adaptation of cells to serum-free conditions, maintain cell viability and reuse the cultures for multiple rounds of protein production. As such, an efficient single step affinity process to purify recombinant proteins from serum-containing medium was optimized. Furthermore, a series of multi-cistronic vectors were designed to enable simultaneous expression of proteins and their biotinylation in vivo as well as fast selection of protein-expressing cell pools. Combining these improved procedures and innovative steps, exemplified with seven cytokines and cytokine receptors, we were able to produce biologically active recombinant endotoxin free protein at the milligram scale in 4-6weeks from molecular cloning to protein purification

Novel insights into IL-6 cis- and trans-signaling pathways by differentially manipulating the assembly of the IL-6 signaling complex

The IL-6 signaling complex is described as a hexamer, formed by the association of two IL-6/IL-6R/gp130 trimers, with gp130 being the signal transducer inducing cis- and trans-mediated signaling via a membrane-bound (mb) or soluble (s) form of the IL-6R, respectively. 25F10 is an anti-mouse IL-6R mAb that binds to both mbIL-6R and sIL-6R with the unique property of specifically inhibiting trans-mediated signaling events. In this study, epitope mapping revealed that 25F10 interacts at site IIb of IL-6R yet allows the binding of IL-6 to the IL-6R and the recruitment of gp130 forming a trimer complex. Binding of 25F10 to IL-6R prevented the formation of the hexameric complex obligate for trans-mediated signaling suggesting that the cis- and trans- modes of IL-6 signaling adopt different mechanisms for receptor complex assembly. To study this phenomenon also in the human system, we developed NI-1201, a mAb that targets, in the human IL-6R sequence, the epitope recognized by 25F10 for mice. Interestingly, NI-1201, however, did not selectively inhibit human IL-6 trans-signaling although both mAbs produced beneficial outcomes in conditions of exacerbated IL-6 as compared to a site I-directed mAb. These findings shed light on the complexity of IL-6 signaling. First, triggering cis- versus trans-mediated IL-6 signaling occurs via distinctive mechanisms for receptor complex assembly in mice. Second, the formation of the receptor complex leading to cis- and trans-signaling biology in mice and humans is different which should be taken into account when developing strategies to inhibit IL-6 clinically

Although IL-6 trans-signaling is sufficient to drive local immune responses, classical IL-6 signaling is obligate for the induction of T cell-mediated autoimmunity

IL-6–mediated T cell-driven immune responses are associated with signaling occurring through the membrane-bound cognate receptor α-chain (mIL-6Rα). Once formed, IL-6–mIL-6Rα complexes induce the homodimerization and subsequent phosphorylation of the ubiquitously expressed signal-transducing protein, gp130. This signaling event is defined as classical IL-6 signaling. However, many inflammatory processes assigned to IL-6 may be mediated via binding a naturally occurring soluble IL-6Rα, which forms an agonistic complex (IL-6/soluble IL-6Rα) capable of evoking responses on a wide range of cell types that lack mIL-6Rα (IL-6 trans-signaling). To dissect the differential contribution of the two IL-6 signaling pathways in cell-mediated inflammatory processes, we pharmaceutically targeted each using two murine models of human arthritis. Whereas intra-articular neutralization of trans-signaling attenuated local inflammatory responses, the classical pathway was found to be obligate and sufficient to induce pathogenic T cells and humoral responses, leading to systemic disease. Our data illustrate that mechanisms occurring in the secondary lymphoid organs underlying arthropathies are mediated via the classical pathway of IL-6 signaling, whereas trans-signaling contributes only at the local site, that is, in the affected tissues