IFNB1 and systemic lupus erythematosus: In addition, an increase in the serum concentration of IFN-I (IFN-β) has also been described in this lupus-like mouse model [18], and this cytokine could induce the expression of Ifnb1 and Tlr9 [51,52,53], which were also found here to be over-expressed in the NK1.1+, CD4+ T cells from mice that produce IgG anti-NPA antibodies.