FUT4 and rheumatoid arthritis: Glycans with multiple branches, sialylation, and a consequently induced sialyl Lewis X (SLex) epitope, which involves the structure of outer branch fucosylation and sialylation [18] and is related to leukocyte-endothelial adhesion [19], were reported to increase in various chronic inflammatory diseases, including rheumatoid arthritis [20], Crohn's disease [21], and cancers [21]–[23].