DNA Damage Repair Pathways Play a Critical Role in Myeloid Differentiation

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PROJECT SUMMARY Differentiation of myeloid progenitor cells produces a wide variety of downstream effector cells that are integral components of the innate immune system. During hematopoiesis, monocytes are produced as surveillance units, waiting to receive signals from cytokines identifying regions of inflammation or infection. Induction of differentiation may produce dendritic cells or macrophages, dependent on the signals received, and inflammatory conditions are associated with the release of DNA damaging agents that could potentially impact the function of immune cells. But the mechanisms involved in protecting the differentiated effector cells from DNA damage is relatively under-investigated, particularly for dendritic cells. Therefore, in this proposal we investigate how DNA damage and repair affect the differentiation and activation of dendritic cells. Our preliminary data indicate a major deficiency in the nucleotide excision repair (NER) pathway in dendritic cells, whereas other pathways, including non-homologous end joining and base excision repair remain proficient. Since these pathways specialize in the repair of different types of DNA damage, these data suggest that dendritic cells may be more sensitive to some DNA damaging agents than others. The goals of this proposal are to determine the role of DNA repair during the differentiation and activation of dendritic cells and to determine the effect of dysregulation of the NER pathway on the ability to mount an inflammatory response in the lung. I hypothesize that DNA repair plays a critical role in the differentiation and the function of dendritic cells and that dysregulation of DNA repair diminishes the ability of dendritic cells to activate T cells. In order to study this, I will first determine the effect of DNA damage on the differentiation and activation of dendritic cells. By first isolating human monocytes and then challenging them with a panel of DNA damaging agents during differentiation, I will determine how specific types of DNA damage affect the differentiation of dendritic cells and their ability of to activate T cells in vitro. To determine how inefficient DNA repair affects dendritic cell differentiation and function in vivo, I will investigate the ability of mice deficient in the NER gene, XPC, to induce an inflammatory response after exposure to the immunogenic agent poly(I:C). Analysis of cytokines and cell infiltrates into the bronchoalveolar lavage fluid and intact lung tissue will be utilized in order to determine the change in dendritic cell and T cell activation compared to WT controls. Completion of this project will yield new insights into the roles of DNA damage and repair in dendritic cell differentiation and function, and will provide a foundation for understanding and possibly controlling immune responses in patients, particularly under conditions that promote DNA damage including cancer therapy, inflammation, and inhaled toxicants.