Surface KKO binding on monocytes compared with macrophages. (A) Human (left) and mouse (right) studies of relative KKO binding as in Figure 1A to cultured unstimulated monocytes (□) and concurrently studied LPS-stimulated monocytes (♦). The murine cells were isolated from a mPF4^KO mouse. N ≥ 3, each in duplicate. Mean ± 1 SE are shown. *P < .05 for relative binding to stimulated cells versus resting cells. (B) mPF4^KO mice cultured, unstimulated monocyte (○), and concurrently studied LPS-stimulated monocytes (♦) at 2 different PF4 concentrations and different heparin concentrations as in Figure 1B. N ≥ 3, each in duplicate. Mean ± 1 SE are shown. *P < .05 for relative binding to stimulated cells versus unstimulated cells.