A, effects of three synthesized siRNAs for knocking down MyD88 expression were analyzed after transfection from 24 h to 96 h by semiquantitative RT-PCR. Results of the effective siRNAs 1 and 3 are shown. B, semi-quantative RT-PCR showed increased Ig µ expression after stimulation by CpG 2006, CpG 2078 and GpC (upper panel). This was abolished by MyD88 knockdown with siRNA1 and siRNA3 (lower panel). GAPDH, internal control. C, flow cytometry analysis showed that the cytoplasmic IgM level was decreased after stimulation with CpG 2006, CpG 2078 and GpC, and that this was abolished by MyD88 knockdown with siRNA1 and siRNA3. **P<0.01 vs. vehicle control. D, Western blot analysis showed that the cytoplasmic IgM level was decreased after stimulation with CpG 2006, CpG 2078 and GpC, and that this was abolished by MyD88 knockdown with siRNA1 and siRNA3.