Neutralization of HMGB1 decreases Fas-induced pro-inflammatory cytokine production by mϕ. Primary murine peritoneal mϕ were pretreated with anti-HMGB1 mAb (0.25 μg/ml) or isotype control IgG2b (0.25 μg/ml) for 1 hr, prior to stimulation with mFasL (0.25 μg/ml) for the times indicated (0 - 18 hr) as described in Materials and Methods. Pro-inflammatory cytokine production was determined by measurement of (A) TNF-α (4A) and (B) MIP-2 (4B) in culture supernatants by cytokine-specific ELISAs as described in Materials and Methods. Data are presented as mean ± SD of 3 independent experiments, n = 3/group. * P ≤ 0.05; **P ≤ 0.01.