Hierarchy of DAF-FM–associated fluorescence intensity in human blood cells. (A-C) Blood was separated into platelet-rich plasma, leukocytes, and red blood cell fractions and loaded with DAF-FM diacetate. Blood cell subpopulations within each fraction were identified by flow cytometry on the basis of their FSC/SSC distribution (i) and by surface marker discrimination (not shown). The distribution of the green fluorescence signal measured in each gate is depicted in panel ii. L-lymphocytes, M-macrophages, PLT-platelets, PMN-polymorphonuclear granulocytes, RBC-red blood cells; SSC-side scatter, FSC-forward scatter. (D) Specific intracellular fluorescence of blood cell subpopulations (assessed as ΔMFI = median fluorescence intensity − background fluorescence) plotted in relation to blood composition (ie, relative levels of each cell in blood; right y-axis; n = 4; ANOVA P = .0002: Bonferroni versus monocytes **P < .01; ***P < .001, #t test P < .001).