To identify serum biomarkers that can be used to monitor GCA activity and could inform on the ongoing vascular inflammation, we determined serum levels of a predefined set of proteins (SAA, IL-6, IL-8, IL-18, IL-23, CHI3L1) in 25 GCA patients who responded to therapy at T0 and at weeks 4, 12, 24, and 48 of follow-up. Here, CHI3L1 is linked to temporal arteritis.