Induction of high levels of GM-CSF Secretion in Human Peripheral Blood Mononuclear Cells by non-CpG Immunostimulatory Oligonucleotides

RODRÍGUEZ JM, MARCHISIO J, LÓPEZ SALÓN M, ELÍAS F, MONTANER A, FLÓ J, LÓPEZ RA AND ZORZOPULOS J

San Diego, CA. USA

Congreso; Experimental Biology. XXXV International Congress of Physiological Sciences; 2005

American Association of Immunologists

During a study aimed at investigating which cytokines were secreted by human PBMC upon incubation with immunostimulatory ODNs, It was observed that some non-CpG ODNs induced the secretion of small amounts of GM-CSF. Since GM-CSF is a key hematopoietic and immune regulatory cytokine it was of interest to investigate what kind of ODNs were able to induce the secretion of GM-CSF, its structural requirements and its target cells. The study showed that the amount of secreted GM-CSF could be greatly increased upon incubation of human PBMC with the inducer ODNs plus IL2. Structural requirements were: a) the most active ODNs have a high content of Ts b) most of the efficient ODNs are included within the family of PyNTTTTGT immunostimulatory ODNs, which were previously described by our group and c) ODNs containing CpG dinucleotides were inactive or poorly active We also found that IFN á inhibited GM-CSF secretion induced by PyNTTTTGT ODNs and that some CpG ODNs were unable to induce GM-CSF due to the concomitant induction of INFá . GM-CSF quantification from supernatant of purified cells types and intracellular flow cytometric analysis showed that NK and NKT cells were the main ODN stimulated GM-CSF secreting cells. Finally, this GM-CSF stimulation pathway was not affected by chloroquine but heavily depressed by dexamethasone.