Rapid ATP-induced MMP-9 and TIMP-1 release from mononuclear cells of randomly selected healthy individuals (○) and subjects homozygous for the P2X₇ Glu496Ala loss-of-function polymorphism (•). PBMCs (2 × 10⁷/mL) were incubated with or without 1 mM ATP at 37°C in NaCl medium containing 1 mM CaCl₂. Supernatants were collected after 30 minutes, and MMP-9 and TIMP-1 concentrations were measured by ELISA. The genotypes of the P2X7 receptor in those randomly selected healthy donors were unknown at the time of assay.