Figure 3

Pre-fixed platelets but not plastic microbead particles nor lymphocytes mediate regulatory response. (A) Pre-fixed platelets can mediate IgG-bound platelet-induced regulatory response. Paraformaldehyde (PFA)-fixed human platelets and sort-purified monocytes were incubated with an anti-CD61 mAb following LPS stimulation for 24 h. The IL-10 levels in culture supernatants were determined by ELISA. Data are shown as means for triplicate samples ± SEM. The results are representative of more than three independent experiments with similar results. **P < 0.01. (B) Plastic microparticles cannot mimic platelets. Anti-TNP-IgG-coated polystyrene microparticles of different diameters (1, 3, and 4.5 μm) were incubated with mouse bone marrow cells, which were then stimulated with LPS. After 24 h, the IL-10 levels in the supernatants were measured by ELISA. Data are shown as means for triplicate samples ± SEM. The results are representative of more than three independent experiments with similar results. *P < 0.05; **P < 0.01. (C) Sorted lymphocytes cannot mimic platelets. Sort-purified monocytes were subjected to the assaying with sorted lymphocytes or platelets as control in the presence of anti-CD61 mAb and LPS. The IL-10 and IL-12 levels in culture supernatants were determined by ELISA. Data are shown as means for triplicate samples ± SEM. The results are representative of more than three independent experiments with similar results. *P < 0.05; **P < 0.01.