Mobilization of Ca²⁺ and chemotaxis of monocytes. (A) Cells were incubated for 24 hours in the absence or presence of PGE₂ (10⁻⁵ mol/L) or dBcAMP (10^−-4 mol/L), washed, and loaded with Fura-2 AM; increases in intracellular Ca²⁺ upon addition of MIP-1β (100 ng/mL) were measured with a fluorescence spectrophotometer. (B) Chemotactic activity of MIP-1β in a modified Boyden-chamber chemotaxis assay. Data are expressed as means ± SEM of three or more experiments. Statistically significant differences between control and treated cells are indicated (*P < .05, ** P < .02, unpaired t-test; n = 3 to 6 independent experiments).