PAMP stimulation results in enhanced microglial phagocytosis. N9 cells (A) or primary cultured microglia from C57BL/6 mice (B) were pre-stimulated with the PAMPs indicated (Poly I:C, 50 μg/mL; LPS, 50 ng/mL; PGN, 50 μg/mL; CpG-DNA, 1 μM) for 6 hours. Cells were rinsed in complete RPMI 1640 media (containing 5% fetal calf serum and 1 mM penicillin/streptomycin) and then cultured for an additional 1 hour at 37°C or at 4°C (control) with yellow-green fluorescent latex beads (1:1000, Sigma). After extensive rinsing, microglia were subjected to fluorescence-activated cell sorter analysis, and mean fluorescence intensity of cells cultured at 4°C was subtracted from values from cells cultured at 37°C. These figures were then normalized to untreated control microglia to obtain percentage of phagocytosis increase over baseline. Unpaired t-test was used to assess statistical significance for each treatment condition compared to control, with n = 3 wells for each condition presented; ** p < 0.001, * p < 0.05. Abbreviations used: Poly (I:C), polyinosinic : polycytidylic acid; LPS, lipopolysaccharide; PGN, peptidoglycan; CpG-DNA, unmetylated DNA containing CpG motifs.