Fig. 5.

IL-1β mediates induction of IL-6 upon infection with S. aureus. (A) HEK293T cells were transfected with expression plasmids for NOD2, pro-IL-1β, and caspase-1 and were incubated for 8 h with WT or α-hemolysin-deficient (Δ) S. aureus at a MOI of 5. Secretion of IL-1β into the supernatants was determined by ELISA. Data are mean (SD) from 1 representative of 3 independent experiments. (B and C) Nod2^−/−, Il-1R^−/−, Caspase-1^−/−, and WT mice were infected s.c. with 5 × 10⁷ cfu of WT S. aureus. IL-1β mRNA levels (normalized to GAPDH) in the infected skin were determined by real-time PCR and are expressed relative to the levels in uninfected WT mice (n = 5 mice/group). IL-1β and IL-6 levels were assayed by ELISA in skin homogenates (n ≥ 5/group) or serum (n ≥ 5/group). All data are mean (SE); *, P < 0.05.