IL-4 and IL-10 promotes phagocytic activity of microglia by up-regulation of TREM2.

Triggering receptor expressed on myeloid cells-2 (TREM2) is an innate immune receptor that promotes phagocytosis by microglia. However, whether TREM2 is related to the stimulus-dependent phagocytic activity of microglia is unclear. In this study, the primary cultured microglia were stimulated with interferon (IFN)-γ, interleukin (IL)-4, and interleukin (IL)-10, respectively, and their phagocytic activity against microbeads and apoptotic neural stem cells (NSCs) was measured. TREM2 of microglia was detected by qPCR and western blotting. The TREM2 signal was blocked in microglia using the siRNA technique. The results showed that IL-4 or IL-10 treatment significantly increased the number of microglia gathered around the apoptotic neurosphere. IL-4 and IL-10 treatment also promoted phagocytosis of microbeads and apoptotic NSCs by primary cultured microglia. The TREM2 expression was up-regulated in IL-4- or IL-10- treated microglia. TREM2 siRNA treatment blocked the phagocytic activity of IL-4- or IL-10-treated microglia. In conclusion, these results indicated that IL-4 and IL-10 promote the phagocytic activity of microglia by the up-regulation of TREM2, which suggested a new potential therapeutic target for neurodegenerative disease.