ABSTRACT This exploratory/developmental application proposes to interrogate how the divalent cation transporter NRAMP1/SLC11A1 mediates control of Salmonella infection. While the function of this transporter has been studied in macrophages, our studies on the link between vitamin A deficiency and susceptibility to Salmonella bacteremia uncovered an unsuspected role for NRAMP1/SLC11A1 in control of systemic S. Typhimurium infection by neutrophils. This finding goes against the conventional wisdom that SLC11A1-dependent host defenses are associated exclusively with macrophages. If true, this would be a novel concept and would represent a major advance in understanding both the role of SLC11A1 and neutrophil function. The definitive experiment to test this idea would be infection of mice that are conditionally deficient for SLC11A1 only in neutrophils. However, given the reliance of the field on C57BL/6 mouse strains, that express a defective Slc11a1 allele, tools and constructs for generating conditionally defective mice currently do not exist. We propose to fill this gap by generating and utilizing mice carrying a ?floxed? Slc11a1 allele to study cell type-specific roles of SLC11A1 in immunity to bacterial infection. The premise for our proposed approach is strong, as (i) SLC11A1 is critical to controlling intracellular pathogens; (ii) SLC11A1 has been implicated in human autoimmune diseases involving neutrophil function and (iii) we present clear preliminary results supporting a role for SLC11A1 in neutrophil function in vitro. My lab group has enlisted the support of the UC Davis Mouse Biology Program, which is one of the leads in the Knockout Mouse Project (KOMP) consortium and has successfully produced over 950 knockout mouse lines. Further, we have a set of tools and assays established in our lab to successfully complete the proposed studies. Our proposed work is novel and innovative in that the function of SLC11A1 in cell types other than macrophages is not yet known. We will test our hypothesis that SLC11A1 plays a role in neutrophil antimicrobial response in a rigorous manner and with multiple complementary lines of experimentation. This work is significant in that understanding the role of SLC11A1 in the neutrophil will shed light on how neutrophils control disseminated Salmonella infection, and the results are likely to open the door to studies on the role of neutrophils in controlling other pathogens, such as Leishmania and non-tuberculous mycobacteria, in which SLC11A1 function is important. It is our expectation is that the results of this work will advance our fundamental understanding of neutrophil biology as well as providing tools to study the links between SLC11A1 and other infectious and autoimmune pathologies, in which this transporter has been implicated.