Cluster analysis of genes upregulated by interferons. (a) A subset of genes identified by unbiased clustering analysis were responsive to both IFN and IFN, but not IL-4. On average, the expression of these genes was upregulated by 36.3% in SLE. (b) Ten focus genes identified as being upregulated in four cell types in SLE were examined in the cytokine-treated cells. These genes also exhibited increased expression after IFN and IFN treatment but not IL-4 treatment.