Fig.7.

TREM2 protein is involved in phagocytosis and is required for myeloid cells survival. In human bone marrow, TREM2 (green) protein was expressed in myeloid progenitor cells and co-localized with mesenchymal cell markers anti-CD42b (a). Similarly, to human mesenchymal stem cells (MSC), both TREM2 (red) and CD42b (green) were present (b), and showed some co-localization in monocytic cell line THP1 (c). A bright field image of normal THP1 cells (d) and after 24-h post-treatment with rat RBCs showed total phagocytosis of RBCs inside the THP1 cells (e-f) and co-localization with CD42b (g). RBC-treated THP1 cells were stained with TREM2 and found to be co-localized with EEA1 (green) (an early endosome marker) (h) and LAMP1 (a late endosomal marker) (i), suggesting that TREM2 protein participates in endocytosis and phagocytosis. WB analysis was performed with rat-RBC treated and untreated THP1 cell lysate. TREM2 protein levels increased at least four-fold post-RBC treatment (m & n, p < 0.0001). THP1 cells were transfected with human TREM2 anti-sense oligonucleotides, cells were stained with anti-TREM2 and anti-DAP12 antibodies. Very faint TREM2 expression was visible (j-l). Cells were collected and a WB analysis was performed with an anti-TREM2 antibody. TREM2 expression was visible in the control cells but not in the siRNA treated cells (o & p, p < 0.0001). Error bars indicate SEM. ^***p < 0.0001. The scale bar in a-c and g-i = 25μm, d-f and j-l = 50μm.