Dendritic cells (DCs) realize a surveillance network in tissues. Due to their location are influenced by the environment and transmit danger signals to cells from the adaptive immune system. It has been shown that they could release microvesicles, however quantitative measurements as well as functional studies are unclear. Thus we have investigated the microvesicles released from LPS stimulated DCs, and did look at their capacity to transfer of allo-antigens by fusing with plasma membrane of resting DCs in cocultures.
DCs labeled with a fluorescent lipophilic tracer and trapped in collagen matrix were visualized with laser scanning microscopy. Using a surpass algorithm we were able to identify and quantify per cell, secreted microvesicles after LPS stimulation. These microvesicles seem to originate from DCs plasma membrane, 90% of them having a diameter between 0.2µm to 0.4µm and are released as a function of the danger signal such as LPS. We then examined the interaction of plasmic membrane-vesicles labeled with a second lipophilic tracer, with DCs at distance not yet activated by danger signals. By a double vital staining we have been able to find that isolated microvesicles from activated DCs can fuse with the membrane of resting DCs raising its capacity to present allo-antigens to lymphocytes. We concluded that DCs are able to respond to danger signals by the release of microvesicles. They can fuse with resting DCs in a distance amplifying potentially the immunological response by DCs network after only few hours following stimulation