[57] A polypeptide obtainable by a process comprising stimulating THP-1 cells with phorbol myristate acetate (PMA) for about 30 min, washing the cells free of PMA, harvesting culture medium from the washed cells, and then substantially purifying the polypeptide from the culture medium, wherein the polypeptide has enzymatic activity for cleaving and releasing tumor necrosis factor (TNF) receptors expressed on the surface of cells.