Concentration-dependent effect of antagonizing IL-1 activity. Healthy human cartilage was cultured for 4 days in the absence (control; dotted line) or presence of 50% blood. During blood exposure, an IL-1βmAb (A, C, E; n = 8) or an IL-1RA (B, D, F; n = 7) was added. Proteoglycan synthesis rate (A, B), release (C, D), and content (E, F) are depicted. #P < .05 compared with control values; *P < .05 compared with blood-exposed cartilage without IL-1βmAb or IL-1RA addition.