TLR-ligation on human microglia by LPS protected microglial cells from NK cell-mediated cytotoxicity (Fig. 7A), *p=0.02. In contrast, monocyte-derived macrophages were more susceptible to NK cell mediated cell lysis following LPS stimulation (Fig. 7C), **p=0.004, whereas matured DCs were less susceptible (Fig. 7B), ***p<0.001. In addition, LPS stimulation resulted in an up-regulation of MHC class I surface expression on microglial cells and the protective effect of microglia activation could be reversed by MHC class I blockade, *p=0.002, indicating that this effect was primarily MHC class I-mediated (Fig. 7D). At least 3 experiments for each cell-type are summarized.