T lymphocytes are activated by the recognition of antigenic peptides associated with histocompatibility molecules present on the surface of antigen-presenting cells: dendritic cells. The type of T cell response (TH1, TH2, TH17...) is determined by the context of this presentation and the involvement of receptors for innate immunity molecules of microbial origin present in dendritic cells. The biology of dendritic cells, in their role as signal integrators, has made considerable progress in recent years. The specialization of these cells, their origin and differentiation patterns have been largely clarified, as have their numerous functions. The presence of specialized dendritic cells within tissues accounts for the induction of immune responses adapted to each environment. Signals transmitted to T lymphocytes enable the differentiation of specialized effector cells involved in specific mechanisms of anti-infectious immunity. The main transcription factors governing these programs have been identified. Nevertheless, a certain plasticity of effector T lymphocytes has been observed, some being endowed with multiple or evolving effector capacities. Ongoing analyses of the transcriptional regulation of the key genetic loci of these programs should shed light on the epigenetic mechanisms involved in this fine modulation of the characteristics of adaptive immune responses at the single-cell level.
The lecture was followed by a seminar entitled "Dendritic cells and immune responses" given by Dr. Sébastian Amigorena, a researcher at the Institut Curie and one of the leading experts on the biology of these cells. S. Amigorena has made a particular contribution to the study of "cross-presentation" mechanisms, which enable dendritic cells to present antigens of exogenous origin to CD8 T lymphocytes. This mechanism of antigen presentation makes a decisive contribution to anti-infection and anti-tumor immunity.
