SAA1(46-112) does not induce chemokines in monocytes but synergizes with CCL3 to chemoattract monocytes. (A) CD14⁺ monocytes were incubated with different concentrations of LPS (500 or 5000 ng/mL), hu rSAA1α (1-1000 ng/mL), bo SAA1(46-112) (1-3000 ng/mL), hu SAA1(47-104) (1-3000 ng/mL), or control buffer (Co). Cell supernatants were taken 2 hours after induction. The amount of CCL3 (Ai) and CXCL8 (Aii) produced by the stimulated cells was measured in a sandwich ELISA. Data represent the mean production ± SEM from 3 (Ai) or 3 to 5 (Aii) independent experiments. A dashed line indicates the detection limit of the ELISA (Ai). Averages below the detection limit are shown without SEM. Statistically significant differences compared with controls are indicated by asterisks (*P ≤ .05; Mann-Whitney U test). (B) The chemotactic potency of CCL3 (0.1-1 ng/mL), SAA1(46-112) (1000 and 3000 ng/mL), hu rSAA1α (3000 ng/mL), or a combination of CCL3 and SAA1(46-112) or rSAA1α was evaluated on CD14⁺ monocytes in the Boyden microchamber assay. Data represent the mean CI from 6 to 7 independent experiments. Statistically significant synergy is indicated by daggers (compared with the sum of the net CI values when both chemotactic agents are tested separately; ^†P ≤ .05; Mann-Whitney U test).