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Figure 4 | Journal of Neuroinflammation

Figure 4

From: Myelin down-regulates myelin phagocytosis by microglia and macrophages through interactions between CD47 on myelin and SIRPα (signal regulatory protein-α) on phagocytes

Figure 4

CD47 on myelin and serum can each promote SIRPα-dependent down-regulation of myelin phagocytosis in microglia with reduced SIRPα levels. (A) Quantitation of SIRPα levels in Balb/C microglia infected with SIRPα-shRNA (SIRPα-KD) or non-target control Luciferase-shRNA (Con-Luc) based on (B) immunoblot analyses in which SIRPα and GAPDH levels were determined. An SIRPα to GAPDH ratio in SIRPα-KD microglia was calculated as a percentage of that ratio in Con-Luc microglia, which was defined as 100%. Values of individual experiments, averages ± SE and levels of significance are given; two tailed p-value of significance is *** p < 0.001. Phagocytosis of CD47+/+ myelin is augmented in SIRPα-KD microglia compared to phagocytosis by Con-Luc microglia in both (C) the presence and (E) the absence of serum. Phagocytosis of CD47-/- myelin is augmented in SIRPα-KD microglia compared to phagocytosis by Con-Luc microglia in (D) the presence but not (F) the absence of serum. Phagocytosis by SIRPα-KD microglia was calculated as a percentage of phagocytosis by Con-Luc microglia, which was defined as 100% (see Methods). Values of individual experiments, each performed in triplicates, averages ± SE and levels of significance are given; two tailed p-value of significance are ** p < 0.01 and *** p < 0.001.

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