SPP1 and lupus nephritis: It is important to note that the six biomarkers in our BPMA-S6 are representative of several major pathogenic pathways of lupus nephritis, including autoantibody production and B-cell activation or migration (anti-dsDNA, VCAM-1, ALCAM) (59–61), T-cell activation (ALCAM, OPN, TNFRSF1B) (48, 62, 63), and complement activation (VSIG4) (55).