Skip to main content
. 2021 Mar 11;12:644725. doi: 10.3389/fimmu.2021.644725

Figure 4.

Figure 4

Detection of CXCL8 by top down-tandem mass spectrometry proves proteolytic activation in synovial fluids of arthritis patients. Total CXCL8 was extracted from synovial fluids of RA (n = 14) and JIA patients (n = 12) by immunosorbent isolation and subjected to nano-LC-MS/MS analysis. For each sample, two top-down nano-LC-MS/MS runs were performed to examine the presence of eight CXCL8 forms in MRM mode. (A) Extracted ion chromatograms (EIC) show the intensity of m/z values of signature fragment ions (±0.5) generated by fragmentation of a specific precursor ion (indicated between brackets) during protein elution. A representative experiment is shown (RA patient). (B) Representative fragmentation spectra confirm the presence of signature ions of CXCL8(1-77), CXCL8(6-77), CXCL8(7-77), CXCL8(8-77) and CXCL8(9-77) in synovial fluid from a patient with RA. (C) Relative abundance of CXCL8 proteoforms in synovial fluids from RA and JIA patients (represented as mean ± SEM).