FIGURE 2.

Microglial cytokine responses to S. pneumoniae lysates are significantly smaller than those elicited by intact bacteria and are not dependent on the expression of NOD2. Microglia (2 × 10⁶ cells per well) from wild type (NOD2+/+) (Panels A and C) or NOD2 knockout (NOD2-/-) (Panels B and C) animals were untreated or exposed to either viable S. pneumoniae (MOI, of 25:1, 75:1, 250:1 bacteria to each glial cell) or lysates derived from an equal number of bacteria. At 24 hrs following bacterial challenge culture supernatants were isolated and assayed for the presence of IL-6 and TNF-α by specific capture ELISA. Data are presented as the culture supernatant cytokine concentrations (Panels A and B) and as fold increases over levels in unstimulated cells (Panel C) and are the means of triplicate determinations of samples from three separate experiments +/- SEM. Asterisks indicate statistically significant differences in cytokine production between cells treated with intact bacteria or bacterial lysates (p < 0.05).