Final Activity Report Summary - WASPTRAFFICDC (Trafficking of DC in Wiskott Aldrich Syndrome) Wiskott-Aldrich Syndrome (WAS) is caused by gene mutations that result in lack of expression of a specific protein called Wiskott-Aldrich Syndrome protein (WASp). As a result, patients who suffer from this rare X-linked immunodeficiency, do not have a fully functional immune system as all cells of the immune system lack WASp and consequently fail to function properly. An important regulator of immune responses is a particular type of immune cell called dendritic cell (DC). In our research we have been investigated the mechanism how defective function of DCs in WAS contribute to failing of the immune system. We have observed that WAS DC fail to activate T cells, which are important effector immune cells and crucial in establishing effective long-term protection against bacteria and viruses. Our research has investigated the interaction between DC and T cells and we have observed that lack of WASp causes failure to form the signalling structure between DC and T cells, which normally mediates activation of T cells and is responsible for the initiation of a protective immune response. Our research is providing insights into the pathophysiology of WAS and contributes to better understanding of how DCs interact with T cells in general. In particular, our findings highlight the importance of correcting DC function in WAS for therapeutic intervention.