FUT4 and rheumatoid arthritis: Further identification of the most abundant immune cells within synovial tissue expressing the different components of the prostanoid system showed predominantly granulocytes (CD15) and fibroblast-like synoviocytes (P4HB) in JT patients, mainly macrophages (CD68) and fibroblast-like cells (P4HB) in OA patients, and mostly plasma (AB-1), macrophages (CD68), and fibroblast-like-synoviocytes (P4HB) in RA patients.