Effect of inflammatory microcrystals on prostanoid synthesis by human monocytes. (A) Monocytes were incubated for 24 hours with either MSU or CPPD crystals at the indicated concentrations and cell-free supernatants were analyzed for prostanoid (PGE₂and TXB₂) synthesis. Data obtained from 3 donors are presented, and values are the mean ± SD of duplicate determinations. (B) Monocytes were incubated with MSU crystals (0.6 mg/mL) for the indicated times and prostanoid synthesis was measured. Data obtained from 3 donors are presented, and values are the mean ± SD of duplicate determinations. (C) Monocytes were stimulated in the absence (C), or presence of either MSU or CPPD crystals (0.6 mg/mL) for 24 hours and prostanoid synthesis was measured. When compared with control cells, MSU microcrystals induced significant prostanoid synthesis, *P < .01 (by t test). Data presented are the mean ± SD from at least seven experiments.