CBLN1 and rheumatoid arthritis: The concentration of total Cer species was 1.4 nmol/ml in SF from controls, elevated 2-fold in SF from eOA (2.8 nmol/ml; n.s.), 3.9-fold in lOA SF (5.5 nmol/ml; p≤0.01), and 3-fold in SF from RA (4.2 nmol/ml; p≤0.001).