What is the ligand in the given input?
1) Unmethylated CpG oligonucleotides (ODN)
2) Methylated CpG oligonucleotides (ODN)
3) CpG oligonucleotides (ODN)
4) Unmethylated CpG oligonucleotides (ODN) and Methylated CpG oligonucleotides (ODN)