SAA1(46-112) is not chemotactic for monocytes and neutrophils. (A,C) The chemotactic activity of hu rSAA1α (30-3000 ng/mL) and SAA1(46-112) (10-10 000 ng/mL) was evaluated on human CD14⁺ monocytes (A) and fresh neutrophils (C) in the Boyden microchamber chemotaxis assay. Data are presented as the mean number of migrated cells ± standard error of the mean (SEM) and are pooled from 3 to 14 (A) or 4 to 11 (C) independent experiments. (A,C) Statistically significant migration of leukocytes compared with controls is indicated by asterisks (*P ≤ .05; **P ≤ .01; Mann-Whitney U test). (B) Peripheral blood mononuclear cell (PBMC)–derived adherent monocytes were stimulated with hu rSAA1α (300-3000 ng/mL) or SAA1(46-112) (300-3000 ng/mL). The amount of phosphorylated ERK1/2 in the cell lysate was determined by ELISA. Mean values ± SEM are shown as percentages of control and are derived from 4 to 6 independent experiments. Statistically significant ERK1/2 phosphorylation induced by SAA compared with medium-treated cells is indicated by asterisks (*P ≤ .05; **P ≤ .01; Mann-Whitney U test).