Effector cells of the myeloid lineage (monocytes, macrophages, myeloid dendritic cells, granulocytes) represent a first line of defense against microbial challenges. Through a limited number of pattern recognition receptors, including the recently discovered family of toll-like receptors (TLR) they recognize microbial structures that are present in many pathogens but absent from host tissues and respond to microbial infection in a cell-type specific manner. The main purpose of our project is to investigate TLR signaling pathways in primary human innate immune cells, which have rarely been studied so far. We propose to establish a differentiation model based on peripheral blood stem cells which are transduced with retroviral constructs to express dominant negative forms of TLR signaling pathway components and are subsequently differentiated into mature myeloid cell types in vitro. This approach should allow the investigation of several important aspects of TLR biology. These include among others the identification of signaling pathways used by particular microbial patterns or the role of TLR-induced signaling pathways during differentiation and activation of human myeloid cells (e g the maturation of dendritic cells which represent an important link between innate and adaptive immunity). The proposed project will further our understanding of innate immune defense mechanisms in humans and may lead to new therapeutic strategies for a number of inflammatory diseases.
