Figure 7.

ApoD alters the phagocytosis of myelin by cultured peritoneal macrophages. (A) Myelin phagocytosis by TG-elicited macrophages measured with flow cytometry after different times of exposure to myelin of WT or ApoD-KO mouse brains. Histograms of a representative experiment in WT macrophages are shown. The histogram of control macrophages without myelin defines the fluorescence threshold to classify an event as a DiI-positive macrophage. (B) Flow cytometry evaluation of myelin phagocytosis by TG-elicited macrophages (WT macrophages, upper panel; KO macrophages, lower panel). Dots in graphs represent average ± SD of 3–4 independent experiments (with 3 macrophage samples per experiment) performed with two myelin preparations/genotype, each purified from 1 to 2 mouse brains. Curve fitting was performed following a single exponential and setting a maximal phagocytosis at 5 h following (Slobodov et al., 2001). ApoD-KO myelin delays macrophage phagocytosis independently of the macrophage genotype. (C) Slope of data shown in B for WT and ApoD-KO macrophages, representing the accumulation rate of DiI-positive macrophages. (D) The exogenous addition of purified human ApoD to ApoD-KO TG-elicited macrophages rescues the WT levels of myelin phagocytosis in a concentration dependent manner. Statistical differences were assayed by ANOVA followed by a Multiple Comparison Holm-Sidak test (B), and Student's t-Test (C,D). Asterisks show statistically significant differences (P < 0.05).