Investigation of type-I interferon regulated gene expression in murine dendritic cells
Dendritic cells (DCs) provide a vital link between the innate and adaptive immune systems, allowing for detection of invading pathogens and the rapid initiation of an appropriate response. Until recently, research on type-I interferons (IFN-I) has focused on their function as viral inhibitors. However, it is now evident that IFN-I also has multiple roles in immune regulation, including the alteration of DC function. IFN-I has been shown to enhance T and B cell responses in vivo through stimulation of DCs, but the mechanisms by which IFN-I acts on DCs to produce these effects are unclear. We have investigated how gene expression is altered in IFN-I treated DCs, with the aim of identifying IFN induced genes which enhance the ability of DCs to initiate and sustain an effective immune response. Murine splenic CD1 lc+ DCs or bone marrow-derived DCs were isolated and cultured either alone or in the presence of IFN-I, and two techniques were employed for discovery of differentially expressed genes: representational difference analysis (RDA) and microarray analysis. We identified IFN-I induced genes involved in diverse aspects of cell function, including transcription factors, signaling molecules, co-stimulatory molecules, cytokines and chemokines. For further study, we selected genes which encode putative cell surface proteins or which share homology with proteins involved in adaptive immune functions. Investigation of a putative chemoattractant receptor, Gpr33, showed that expression of this molecule was upregulated in DCs in response to IFN-I both in vitro and in vivo. We attempted to generate antibodies against Gpr33 and have studied mRNA expression by real time PCR. Gpr33 mRNA expression was shown to be upregulated by IFN-I in all splenic DC subsets, but was expressed in the CD8+ subset at levels more than 40 fold higher than the CD4+ subset, indicating that it may specifically be involved in the migration of this subset.