A common class of receptors for the two types of porcine interleukin-1 on articular chondrocytes.

IL1 causes chondrocyte-dependent degradation of the proteoglycans of the extracellular matrix of cartilage. The two types of porcine IL1 (pI5 and 8) were radiolabelled with 125I by use of the Bolton and Hunter reagent. Both labelled IL1s were fully active on cartilage. IL1/8 bound specifically to porcine articular chondrocytes. From Scatchard analysis there were calculated to be about 7,000 sites per cell with Kd 2.5 X 10(-10). All the bound radiolabelled ligand was displaceable with unlabelled IL1/8 or IL1/5 at similar concentrations. It was concluded that chondrocytes express a receptor site that reacts with either IL1.