Mouse type IIFN-producing cells are immature APCs with plasmacytoid morphology

dWe show here that mouse interferon-alpha (IFN-alpha)-producing cells (mIPCs) are a unique subset of immature antigen-presenting cells (APCs) that secrete IFN-alpha upon stimulation with viruses.. mIPCs have a plasmacytoid morphology, can be stained with an antibody to Ly6G and Ly6C (anti-Ly6G/C) and are Ly6C(+)B220(+)CDIIc(10)CD4(+); unlike other dendritic cell subsets, however, they do not express CD8 alpha or CDIIb. Although mIPCs undergo apoptosis in vitro, stimulation with viruses, IFN-alpha or CpG oligonucleotides enhanced their survival and T cell stimulatory activity. In vivo, mIPCs were the main producers of IFN-alpha in cytomegalovirus-infected mice, as depletion of Ly6G(+)/C+ cells abrogated IFN-alpha production. mIPCs produced interleukin 12 (IL-12) in response to viruses and CpG oligodeoxynucleotides, but not bacterial products. Although different pathogens can selectively engage various APC subsets for IL-12 production, IFN-alpha production is restricted to mIPCs' response to viral infection.