The generation of a B7 conditional knockout mouse (63.27)

Abstract B7.1/B7.2 molecules are ligands for CD28 and CTLA-4, major T cell co-stimulatory and co-inhibitory molecules, respectively. B7.1/B7.2 molecules are essential not only for eliciting normal immune responses through CD28 mediated T cell activation, but also for maintaining immune homeostasis via CTLA-4 mediated negative regulation of T cell function. B7/CD28 interaction is critical for development and maintenance of specific immune cell populations, including iNKT cells and Foxp3+ regulatory T cells. Although many cell types (i.e., TEC, DC, MΦ, B cell and T cell) express B7 molecules in vivo, the precise role of B7 on each cell type for immune cell development and immune response is not well defined. To address these questions, we here report the generation of a B7 conditional KO mouse. Since B7.1 and B7.2 have largely redundant roles in vivo, we generated B7.1flox BAC Tg mouse on B7.1/B7.2 DKO background (designated as B7flox). The pattern of B7.1 expression in the B7flox mouse is comparable to that of WT mouse regarding both expression levels and tissue distribution. Cre-dependent deletion of B7.1 expression appears to be efficient in the B7flox mouse, and studies are in progress to evaluate tissue specific roles of B7 in immune system development, homeostasis, and response by tissue-specific Cre-mediated deletion.