SAA1(46-112) does not induce CXCL6 in murine peritoneal cells but cooperates with CXCL6 to recruit neutrophils in vivo. (A) Peritoneal lavages (5 mL per mouse) from 2 female NMRI mice were pooled and incubated with different concentrations of LPS (50-5000 ng/mL), hu rSAA1α (10-1000 ng/mL), or SAA1(46-112) (300-10 000 ng/mL) or were left untreated. Cell supernatants were taken 24 hours after stimulation and the mu CXCL6 levels were determined via a sandwich ELISA. Data represent the mean optical density (OD) ± SEM from 8 to 9 experiments. (B) Female NMRI mice [7-16 (Bi) or 13-25 (Bii) mice per group] were injected intraperitoneally with 200 µL PBS, mu CXCL6 (100 ng in 100 µL + 100 µL PBS), hu rSAA1α (100 or 1000 ng in 100 µL + 100 µL PBS; Bi), SAA1(46-112) (3 or 10 µg in 100 µL + 100 µL PBS; Bii), or a combination of CXCL6 (100 ng in 100 µL) and rSAA1α (100 ng in 100 µL; Bi) or SAA1(46-112) (10 µg in 100 µL; Bii). Peritoneal lavages (5 mL) were obtained 2 hours after injection. The percentage neutrophils (CD11b⁺Gr1⁺ cells) migrated into the peritoneal cavity toward the chemotactic agent(s) was evaluated by flow cytometric analysis. The mean percentage neutrophils ± SEM is shown. (A-B) Statistically significant differences compared with controls are indicated by asterisks (*P ≤ .05; **P ≤ .01; ***P ≤ .001; Mann-Whitney U test) and statistically significant increase in the percentage of neutrophils recruited into the peritoneal cavity (compared with the values of mice injected with mu CXCL6 alone) is indicated by daggers (^†P ≤ .05; Mann-Whitney U test).