B7-1/B7-2 Costimulation Regulates Plaque Antigen–Specific T-Cell Responses and Atherogenesis in Low-Density Lipoprotein Receptor–Deficient Mice

Background— Several lines of evidence indicate that T-cell responses influence the progression of atherosclerotic disease. Interferon-γ (IFN-γ)–producing T cells specific for lesional antigens, including oxidized LDLs and heat shock protein 60 (HSP60), may promote lesion development as well as plaque instability. B7-1 and B7-2 are closely related molecules expressed on antigen-presenting cells that provide costimulatory signals for T-cell activation. This study tested the hypothesis that the ability of T cells to influence atherosclerosis depends on B7-1/B7-2 costimulation. Methods and Results— B7-1/B7-2/LDL receptor (LDLR)–deficient mice and LDLR-deficient control mice were fed a 1.25% cholesterol or control diet for 8 and 20 weeks. Total serum cholesterol levels and extent and phenotype of atherosclerosis were analyzed. Splenic and lymph node CD4 + T cells from the animals were cultured with mouse recombinant HSP60 or media and antigen-presenting cells and analyzed for IFN-γ and interleukin-4 production. The absence of B7-1 and B7-2 significantly reduced early cholesterol diet–induced atherosclerotic lesion development in LDLR-deficient mice compared with B7-1/B7-2–expressing control mice. Furthermore, CD4 + T cells from the cholesterol-fed B7-deficient mice secreted a significantly lower amount of IFN-γ in response to mouse HSP60 in vitro than did T cells from B7-expressing control mice. Conclusions— The data show that B7-1 and B7-2 regulated the development of atherosclerotic lesions and the priming of lesional antigen–specific T cells. This study highlights the B7-CD28 pathway as a potentially important target for immunomodulation of atherosclerosis.