Production of PF4/heparin-specific antibodies in wild-type mice by in vivo CpG challenge and spontaneous production of PF4/heparin-specific antibodies in PKCδ-deficient mice. (A) Production of PF4/heparin-specific antibodies in wild-type mice by in vivo CpG challenge. Wild-type mice were intraperitoneally injected with CpG. At the indicated time points following CpG treatment, sera were collected and tested for mPF4/heparin-specific (left) IgM or (right) IgG production by ELISA. Specificity of the antibodies toward mPF4, mPF4/heparin, and mPF4 in the presence of excess heparin was examined. Each dot represents a mouse, and the horizontal lines indicate the mean values. Data shown are obtained from 8 wild-type mice. (B-E) Spontaneous production of PF4/heparin-specific antibodies in PKCδ-deficient mice. Sera were collected from unmanipulated wild-type (PKCδ^+/+) or PKCδ-deficient (PKCδ^−/−) mice and tested for mPF4/heparin-specific (B) IgM or (C) IgG production by ELISA. Specificity of the (D) IgMs or (E) IgGs toward mPF4, mPF4/heparin, and mPF4 in the presence of excess heparin was examined. Each dot represents a mouse, and the horizontal lines indicate the mean values. Data shown are obtained from 24 wild-type and 17 PKCδ-deficient mice. Statistical analysis was performed with (B-C) the Mann-Whitney test for unpaired data and (D-E) the Wilcoxon signed-rank test for paired data.