SUMMARY
Background
It has been recently demonstrated that inflammatory cells are massively and rapidly recruited following infection with Leishmania. They will secrete immunologic mediators such as cytokines and chemokines in response to Leishmania parasites that will affect the developing immune response, the parasitemia. The crosstalks between neutrophils, macrophages, dendritic cells (DC), and parasites may condition the downstream immune response. However, the contribution of particular DC subsets and their interactions with neutrophils has not been investigated yet. Furthermore, the mechanisms of cell migration to the draining lymph nodes are poorly understood. Work is in progress to determine how these cellular interactions would affect the induction of a protective Th1 response, using different strains of Leishmania.

Working Hypotheses
In addition to their role in killing intracellular pathogens, phagocytes (DC, macrophages and neutrophils) also interact with each other, with consequences on the development of the microbe-specific adaptive immune response. In addition, the pathogen itself modulates the killing activity of the phagocyte to enter, survive, and replicate within specific phagocyte compartments, with impact on the outcome of the immune response (autocrine and paracrine secretion of cytokines, migration of inflammatory cells, antigen presentation). DC lines are valuable tool to predict in vivo behavior of DC.

Specific aims
In this research module, we will combine the expertise of three independent research groups: H. Acha-Orbea’group has expertise in immunology, focusing on the implication of lymphocytes and DC in vivo and in vitro. He will contribute the unique DC lines he established recently in his laboratory. F. Tacchini-Cottier’s group, has expertise in parasite biology, neutrophils and T helper differentiation. She will contribute the Leishmania infection models and the analysis of T helper differentiation, neutrophil analysis in vitro and in vivo, and the analysis of the immune response. B. Imhof’s group has expertise in cell migration and inflammation. He will contribute the JAM KO mice and mAbs directed against JAM molecules, as well as sophisticated in vivo imaging technology. PhD. Candidate 1 will generate DC lines of different subsets and different transduced and KO cell lines and follow their infection; DC activation induced by different Leishmania strains will be assessed by cytokine production and induction of cell surface markers. Many newly produced mAbs directed against DC lines will be screened for their effect on T helper differentiation, first in vitro and then in vivo. PhD. Candidate 2 will analyze the cross talks between neutrophils and DC in the draining lymph nodes, following infection with Leishmania and its impact on the developing immune response, first in vitro, using DC lines representative of specific subsets, as well as ex vivo-derived DC, and then in vivo using susceptible or resistant strains of mice depleted or not of neutrophils, and injected or not with DC cell lines. PhD Candidate 3 will test the role of JAM molecules on the recruitment of inflammatory cells first in vitro and then in vivo to the site of infection