Abstract Plasmacytoid dendritic cells [pDC], also known as type I interferon [IFN] producing cells, play a significant role in the pathogenesis of systemic lupus erythematosus [SLE]. The current study was undertaken to identify novel SLE autoantibody specificities associated with interferon-inducing activity in human pDCs. We found that immune complex mixtures from some Interferon signature negative [IFN−] and all interferon signature positive [IFN+] SLE patients could trigger type I IFN production by pDCs. IgGs from IFN− and IFN+ SLE patients were subsequently screened via a high throughput protein microarray to identify novel auto-antibody specifities that mediate type I IFN production by pDCs. This approach identified five novel autoantibodies that may contribute to type I IFN production by pDCs via a nucleic acid dependent mechanism. The newly identified autoantibody specificities function in a myriad of cell processess and, to date, have not been implicated in SLE pathogenesis.