ABSTRACT: The cause of systemic lupus erythematosus (SLE) is unknown. Interferonα (IFNα) has been suggested as a causative agent of SLE, however, it is not proven, and to what extent and how IFNα contributes to the disease is unknown. We here directly studied the contribution of IFNα to SLE by generating inducible IFNα transgenic mice which showed that conditional up-regulation of IFNα induced a typical manifestation of SLE including serum immune complex (IC), autoantibody against double stranded DNA (anti-dsDNA Ab) and the organ manifestations classical to SLE such as IC-deposited glomerulonephritis, classical splenic onion-skin lesion, and alopecia, epidermal liquefaction, positive lupus-band test of the skin. In the spleen of mice, activated effector CD4 T cells, interferonγ-producing CD8 T cells, B220+CD86+ cells and CD11c+CD86+ cells were increased, and the T cells produced increased amounts of IL-4, IL-6, IL-17 and IFNγ and decreased IL-2. In particular, activated CD3+CD4-CD8- double-negative T (DNT) cells positive for TCRαβ, B220, CD1d-teteramer, PD-1 and Helios, which produced increased amounts of IFNγ, IL-4, IL-17 and TNFα, were significantly expanded. They infiltrated into kidney and induced de novo glomerulonephritis and alopecia when transferred into naïve recipients. Thus, conditional up-regulation of IFNα is sufficient to induce SLE, and the DNT cells as expanded by IFNα are directly responsible for the organ manifestations such as lupus skin disease or nephritis.
