PLAU and rheumatoid arthritis: Accordingly, these lesions express markedly elevated levels of both uPA and uPAR by infiltrating neutrophils, macrophages, and fibroblast-like cells in the inflamed RA synovium (Almholt et al., 2018) and increased plasma levels of soluble uPAR correlate to disease activity (Slot et al., 1999; Enocsson et al., 2021).