Characterization of Calcium signals and oscillations in dendritic cells in vivoin response to pathogens

Abstract

Abstract Dendritic cells (DCs) are disseminated throughout organisms and serve as sentinels, organizing immune responses to infection, tissue damage, and cancer. DCs play a crucial role bridging innate and adaptive immune systems and elicit a tailored adaptive immune response to the types of threats they encounter. Manipulation of DCs is critical for vaccination, and DC-based immunotherapies have been tested in clinical trials as anti-cancer therapeutics and for treatment of infectious diseases. Calcium, a ubiquitous secondary messenger, regulates many critical effector functions of DCs like phagocytosis, maturation, migration, and cytokine production. However, regulation and mobilization of calcium in DCs remains poorly understood. Using microscopy, our preliminary experiments unveiled for the first time an oscillatory calcium signal in DCs in response to whole bacteria; our in vitrostudies show that oscillatory calcium signaling patterns are specific to the type of bacteria. To decipher calcium signals induced by bacterial stimuli in DCs intravitally, we generated CD11c-Salsa6f reporter mice that express the fluorescent protein (FP) construct tdTomato fused to GCaMP6f in CD11c expressing cells. Hence, expression of TdTomato, a red FP, highlights cell shape, and GCaMP6f, which fluoresces green upon calcium binding, visualizes intracellular calcium levels. We are using CD11c-Salsa6f mice to observe calcium signals in DCs in the periphery and in secondary lymphoid organs using two photon microscopy. This model, perfectly suited for intravital two photon microscopy, allows us to unveil bacteria-specific calcium signals in DCs in in their natural microenvironment. Supported by a grant from the NIH (1T32GM139804-01)