OPN was reported to be highly expressed in the MLR/lpr mouse (commonly used model of the human SLE) (Iizuka et al. 1998; Lampe et al. 1991; Miyazaki et al. 2005; Weber and Cantor 2001; Wüthrich et al. 1998). Here, SPP1 is linked to systemic lupus erythematosus.