JAK1 and systemic lupus erythematosus: Figs. 1A, 1C and 2A, 2C, show the results of WB analysis with anti-Jak1 and STAT2 antisera of SLE or healthy control PBMC cell lysates. Basal levels of Jak1 and STAT2 were slightly but significantly higher in SLE patients. As several of the Jak1 and STAT2 WB turned out with two bands, for these studies both bands were used for densitometric quantification. Therefore, values given in Figs. 1 and 2 correspond to the sum of both bands. We assumed that the upper band corresponds to the phosphorylated forms of Jak1 and STAT2 as described [37], which increases in intensity after culture with IFNβ.