Influence of PF4 on the arrest of chemokine-activated monocytes under flow conditions. Monocytic MM6 cells (A) or isolated human blood monocytes (B) were left untreated (control) or stimulated with indicated chemokines (200 ng/mL) (A-B). The relevance of intact GAGs on the cell surface was tested using proteoglycan-degrading enzymes. MM6 cells were preincubated with chondroitinase ABC (0.5 U/mL) for one hour (empty bars in C) and perfused on activated HUVECs. The number of firmly adherent monocytes was determined after accumulation for 5 minutes. Data represent mean ± SEM of at least 3 experiments (*P < .05 as indicated).