CXCL8 and rheumatoid arthritis: Strikingly, the shortest CXCL8 proteins, i.e., CXCL8(8-77) and CXCL8(9-77) which are known to possess up to 30-fold enhanced activity as compared to full-length CXCL8(1-77), were the most abundant CXCL8 proteoforms in synovial fluids from RA patients, representing 23.0 ± 3.0% (mean ± SEM) and 34.6 ± 3.6% (mean ± SEM) of total synovial CXCL8, respectively (Figure 4; Supplementary Table 1).