Le système immunitaire protège un organisme du développement de pathogènes et participe activement au maintien de la tolérance immunitaire. Les cellules dendritiques (DC) sont des cellules spécialisées dans l’équilibre pro et anti-inflammatoire de la réponse immunitaire. Les DC jouent un rôle important dans de nombreux contextes pathologiques notamment la transplantation d’organes, en oncologie et dans les pathologies inflammatoires. Elles sont modulables grâce à divers facteurs, intrinsèques et extrinsèques. Parce qu’elles sont capables d’induire une réponse tolérogène, ces cellules représentent des cibles intéressantes pour moduler la réponse immunitaire dans le contexte de la transplantation d’organes et des pathologies inflammatoires. Certains agents pathogènes utilisent des mécanismes d’échappement au système immunitaire en favorisant l’induction d’une tolérance immunitaire. Cette modulation est réalisée par le ciblage des récepteurs de reconnaissance des pathogènes (PRR) sur la présence des DC, induisant la synthèse d’une cytokine antiinflammatoire IL-10, un des inducteurs de la tolérance immunitaire. Notre stratégie a été de construire un anticorps bispécifique ciblant deux PRR différents à partir d’une banque d’anticorps anti-PRR. Notre travail montre que cet anticorps bispécifique est capable d’orienter les DC vers d’un profil tolérogène. Cet anticorps bispécifique induit un phénotype de DC semi-mature avec un profil de sécrétion pro-tolérogène avec de l’IL-10 et peu de cytokines inflammatoires. Le profil de tolérance immunitaire induite par ces cellules reste à explorer. Nos travaux ouvrent de perspectives intéressantes sur l’association des PRR en vue d’obtenir la modulation des cellules de l’immunité. / The immune system protects an organism from the development of pathogens and actively participates in maintaining immune tolerance. Dendritic cells (DC) are specialized cells in the balance and anti-inflammatory immune response. DC play an important role in many pathological contexts, including organ transplantation, oncology and inflammatory diseases. Various factors, both intrinsic and extrinsic, can modulate. Because they are capable to inducing a tolerogenic response, these cells represent interesting targets for the immune response in the context of organ transplantation and in inflammatory pathologies. Some pathogens use mechanisms of escape to the immune system by promoting the induction of immune tolerance. This modulation is achieved by targeting the pathogen recognition receptors (PRRs) present on the surface of DC, inducing the synthesis of an anti-inflammatory cytokine IL-10, one of the main inducers of immune tolerance. Our strategy was to construct a bispecific antibody targeting two different PPRs from an anti-PRR antibody library. Our work shows that this bispecific antibody is able to direct the DC to a pro-tolerogenic profile. This bispecific antibody induces a semi-mature DC phenotype with a secretion profile of pro-tolerogenic cytokines such as IL-10 and few inflammatory cytokines. The immune tolerance profile of these DC remains to be explored. Our work opens interesting perspectives on the association of PRRs in order to obtain the modulation of the cells of the immunity.

Interferon-inducible PYHIN protein family includes the DNA-binding proteins, AIM2 and IFI16, which form ASC-caspase 1 dependent inflammasomes, important in immunity against cytosolic bacteria, DNA viruses and HIV. The role of other members of this family in the recognition of DNA and/or regulation of immune responses is unclear. We identified an immune regulatory function of p205, another member of the PYHIN family, in the transcriptional control of immune genes. Knockdown of p205 in macrophages revealed that inflammasome activation due to dsDNA and ligands that engage the NLRP3 inflammasome were severely compromised. Detailed mechanistic analysis showed that loss of p205 was associated with a decrease in Asc mRNA and protein levels. p205 knockdown resulted in reduced RNA Polymerase II-mediated endogenous Asc gene transcription and mRNA processing, suggesting a co-transcriptional control of Asc gene expression. Ectopically expressed p205 induced expression of an Asc gene-luciferase reporter and collaborated with other transcription factors, such as c/EBPβ, p65/RelA, to further enhance expression. p205 knockdown also affected the expression of the immune genes Cd86, Cox2, Cxcl2, Il1α, Il10, Il12α, Il6 and Ifnα in LPS-stimulated macrophages. Together these findings suggest that p205 regulates inflammation through control of Asc gene expression, and other immune genes. Fungal infections activate both caspase 1-dependent and -independent inflammasomes. In an independent study, we show that Paracoccidioides brasiliensis fungal infection also induces caspase 8-dependent non-canonical inflammasome. Caspase 8-dependent IL-1β processing required dectin-1, Syk and Asc. Rip3-/- Casp8-/- mice infected with P. brasiliensis displayed increased fungal load and showed worse disease progression compared to wild type and Rip3-/- mice. These results revealed the importance of caspase 8 in activating and regulating inflammasome responses during fungal infection in vivo.