Immunosuppressive microenvironments block the activity of tumoricidal T and NK cells, allowing cancers to avoid immune elimination. Monocytic myeloid-derived suppressor cells (mMDSC) are an important component of these immunosuppressive milieus. Human mMDSC respond to stimulation via their Toll-like receptors by differentiating into macrophage. Agonists targeting TLRs 1/2 (such as PAM3) induce mMDSC to mature into immumosuppressive M2-like macrophage through a process that involves TNF and IL6. Agonists targeting TLRs 7/8 (such as R848) cause the same precursors to mature into tumoricidal M1-like macrophages, a process in which IL12 plays a central role. The immune suppression mediated by mMDSC is reversed by exposure to TLR 7/8 agonists which thus might be useful adjuncts for tumor immunotherapy.
Overall design
In this study we looked at several time points. hMDSC from four different donors were sorted from PBMC then cultured in the presence of R848, Pam 3 or left unstimulated for 30, 75 and 225 minutes. Late time points included samples from seven donors after 3 days in culture with the same TLR ligands. For microarray experiments total RNA was extracted, amplified into aRNA and coupled to Cy5. Similarly amplified RNA from universal RNA was coupled to Cy3 and used as a reference for each array.
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