TNFRSF9 and systemic lupus erythematosus: Furthermore, ligand-receptor pairs, such as CCL20_CXCR3, FAM3C_CLEC2D, FAM3C_HLA_C, SPN_ICAM1, and TNFSF9_TNFRSF9, had higher mean expression levels in epidermal cells of DLE patients and SLE patients than in those of HCs.