Figure 2.

Effect of maturation and priming with low and high LPS dosages on anti-inflammatory responses of murine brain microglia. Microglia isolated from newborn (orange dots, open columns), adult (green dots, hatched columns), and aged (blue dots, gray columns) mice were primed initially by ultra-low (ULP, 1 fg/ml) or high (HP, 100 ng/ml) doses of LPS, followed by a second stimulation (day 6) with 100 ng/ml LPS. The data were normalized and compared to unprimed microglia (UP Group without any stimulation at day 1 with stimulation at day 6 with a fixed dose of LPS 100 ng/ml). Unstimulated microglia served as negative control (US Group without LPS stimulation neither at day 1 nor at day 6). RNA samples (6 h) and supernatants (24 h) were collected after the 2nd stimulation and analyzed for gene expression of IL-10 (A, n = 4–5), Arg-1 (C, n = 3–5), TGF-β (D, n = 3–5), and IL-4 (E, n = 3–5) (unprimed cells assigned as 1.0) and cytokine production of IL-10 (B, n = 5–6) by ELISA (normalized to total protein concentration). Data shown in scatter dot plots represent means + SEM, ^#p < 0.05 vs. unprimed conditions within each age group (naïve or mature), ^§p < 0.05 vs. adult microglia within each stimulation condition (US, UP, ULP, HP).