In vitro neutrophil migration and platelet-neutrophil rosetting are not affected by serotonin. (A) Migration of isolated murine neutrophils toward serotonin or LTB₄. (B) LTB₄-induced migration of neutrophils that were isolated from WT and Tph1^−/− mice. (C) The capacity to form mixed aggregates was analyzed in isolated neutrophils and a 10-fold excess of thrombin-activated platelets after a 45-minute incubation period. Rosetting was defined as 2 or more platelets binding to 1 neutrophil. N = 4.