Figure 1. Mrp8 dose- and time-dependently induces self-tolerance and cross-tolerance in murine macrophages.

Peritoneal macrophages (A) and BMMs (B) isolated from C3H/HeN mice were pre-stimulated with increasing doses of mMrp8 for 18 h and re-stimulated with 5 μg/ml mMrp8 for 6 h. Naïve murine macrophages stimulated with 100 ng/ml LPS (A,B) for 6 h were used as the positive control. (C,D) Murine BMMs were pre-stimulated with 1 μg/ml mMrp8 for the indicated time periods and re-stimulated with 5 μg/ml mMrp8 for 6 h. Murine peritoneal macrophages (E) and BMMs (F) were pre-incubated with either culture medium (naive) or 1 μg/ml mMrp8 (Mrp8-pretreated) for 18 h and re-stimulated with 100 ng/ml LPS, 100 ng/ml BLP, 5 × 10⁴ CFU/ml heat-killed S. typhimurium (S. typhi) or 7.5 × 10⁴ CFU/ml heat-killed S. aureus for 6 h. TNF-α and IL-6 concentrations in the culture supernatants were assessed by ELISA. Data are presented as mean ± SD of three independent experiments and each experiment was carried out in triplicate. *p < 0.05, **p < 0.01 compared with either naive cells stimulated with 5 μg/ml mMrp8 (A–D) or naive cells (E,F).