Selected phosphorothioate oligodeoxynucleotides containing CpG (CpG-ODN) ac
tivate immune responses, including B-cell proliferation and cytokine produc
tion. The mechanism by which cells detect CpG-motifs is not known. There ar
e conflicting reports in the literature concerning the ability of CpG-ODN l
inked to solid supports to stimulate immunity. We prepared a fluorescent, b
iotinylated CpG-ODN, a reagent that will support the growth of 7TD1 cells,
a murine B-cell hybridoma line that requires CpG-ODN or interleukin-6 (HL-6
) for survival. Stimulation of 7TD1 cell growth was not reduced by complexi
ng biotinylated CpG-ODN to streptavidin, but cell growth was not supported
by CpG-ODN coupled to streptavidin-coated latex, magnetic, gold, or agarose
beads, A fluorescent CpG-ODN was also covalently attached to cyanogen brom
ide-activated Sepharose beads via a 5'-amine group. These derivatized Sepha
rose beads did support 7TD1 cell growth, but incubation of the beads with 7
TD1 cells resulted in the appearance of fluorescence within the cells, sugg
esting that growth stimulation may be due to CpG-ODN leached from the beads
. Our results are consistent with the need for CpG-ODN to be internalized i
nto cells to be immunostimulatory.