GDF15 and common variable immunodeficiency: Although detecting differences in serum markers between CVID patients and HCs was not the primary aim of this study, we also observed that CVID patients overall had significantly higher levels of Cathepsin S, S100A8A9, PARC, and GDF15, as well as significantly lower levels of MMP-9, periostin, Angiopoietin 2, and PAI-1 compared to 40 sex- and age-matched healthy controls (Supplemental Table S2).