The present invention relates to 3'-OH, 5'-OH polynucleotide sequence compositions and methods for activating an immune response in an individual, and more preferably, for activating antigen presenting cells in the individual. In one embodiment, the antigen presenting cell is a dendritic cell. The present invention also includes compositions and methods for activating dendritic cells in vitro. These dendritic cells may then be administered to an individual. Preferred 3'-OH, 5'-OH polynucleotide sequences comprise six bases wherein at least 50% of the bases are guanine and the 5' base is guanine. The compositions may comprise a phosphodiester or phosphorothioate backbone.