The second nucleotide in optimal human CpG motifs was thymidine, while in less active human CpG motifs or optimal murine CpG motifs, it was purines.

• 5′ GTCGTT 3′和 5′ GTCGTC 3′ 2个基序对人B细胞有高度免疫刺激活性 ,第二位碱基均为“T” ,而在小鼠CpG基序中该位碱基为“G”或“A”。