Figure 3.

Innate immune memory response of human monocytes primed with NP alone or together with LPS. Human monocytes isolated from blood of four individual donors (red, green, blue, and yellow symbols) were cultured for 24 h in culture medium alone or containing serum-precoated NP: 5.7 µg/ml AuNP SPH, 1.4 µg/ml AuNP ROD, 2 µg/ml FeOxNP 17 and 2.7 µg/ml FeOxNP 22 alone (light blue columns) or together with 1 ng/ml LPS (orange columns) (line priming in abscissa). Cells were then washed and rested for 6 days in the absence of stimuli, then challenged for 24 h in fresh medium alone or containing 5 ng/mL LPS (m and LPS in the abscissa line challenge). The production of TNFα (upper left), IL-6 (upper right), IL-10 (lower left) and IL-1Ra (lower right) was measured in the 24 h supernatants by ELISA. Data are presented as individual donors’ values (coloured symbols) ± SD and as mean of the individual values (dotted columns). The basal response of control cells (CTR), i.e., primed or unprimed cells rested for 6 days and then exposed for 24 h to medium alone, is shown at the extreme left in each panel (empty columns).