In the severe BD group, enriched proteins were predominantly associated with defense response (SERPINA3, ITIH4, COLEC10, FCN3, SERPINA1, TFRC, C1R, CFP, C8B, ORM2, CDH5, C5, PRDX5, C7, TIMP1, MBL2, ANXA1, F12, ADIPOQ, SERPINF2, RNASE4, AGT, ATRN, TF, PROC, MASP1) and protein activation cascade with complement activation (FCN3, C5, COLEC10, C7, C1R, F12, MASP1, C8B, CFP, MBL2) (Figure 3B). Here, ATRN is linked to Behcet disease.