Figure 4

Activating-type FcγRs but not FcγRIIB mediates IgG-bound platelet-induced regulatory response in a mouse monocyte setting in vitro. (A) Mouse bone marrow (BM) cells were incubated with LPS in the presence of human platelets and an anti-human/mouse CD61 mAb (6E4), and then the production of IL-10 and IL-6 was assessed after 24 h. *P < 0.05; **P < 0.01. (B) Mouse BM cells were incubated with LPS in the presence of "mouse" platelets and anti-human/mouse CD61 mAb 6E4 or anti-human but not -mouse CD61 mAb #33 or cIg, and then the production of IL-10 (left) and IL-6 (right) was assessed after 24 h. #33 mAb did not cause the regulatory response in this all-mouse setting. **P < 0.01; n.s., not significant. (C) Neither granulocytes nor lymphocytes mediate regulatory response. Gr1⁺Ly6G⁻ monocytic, Gr1⁺Ly6G⁺ granulocytic and Gr1⁻Ly6G⁻ lymphoid cells were sorted from BM cells of wild-type B6 or FcRγ-deficient mice, and stimulated with LPS in the presence of "human" platelets and 6E4 or cIg. IL-6 was measured 24 h after stimulation by ELISA. **P < 0.01; n.s., not significant. (D) BM-derived cultured macrophages from wild-type, FcRγ-deficient or FcγRIIB-deficient mice were treated with anti-CD61 mAb 6E4 and stimulated with LPS in the presence of human platelets. The IL-10 and IL-6 levels in the culture supernatants were measured after 24 h. Blank (−) indicates cells with no antibody or stimulator for monitoring spontaneous production of cytokines. 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; n.s., not significant.