To establish a link between the expression of BCAP and that of type I IFN-stimulated genes in human samples, we measured PIK3AP1 expression in our cohort of subjects with SLE and correlated it with the IFN score (based on the expression of IFI27, IFI44L, IFIT1, ISG15, RSAD2, and SIGLEC1). Here, ISG15 is linked to systemic lupus erythematosus.