To confirm these similarities, the effect of “K” ODN on the upregulation of mRNA encoding IFN-β, IL-6, IL-23A, and TNF-α by both cell types was compared. As seen in Figure 1, the response of CAL-1 cells to CpG ODN followed the same kinetics as primary human pDCs. Although the absolute magnitude of these responses differed, their pattern of cytokine production (including IL-23, a cytokine made abundantly by pDCs) were quite similar, reinforcing the conclusion that CAL-1 cells mimic the response of human pDCs to “K” ODN stimulation. Subsequent studies focused on identifying the signals are involved in the regulation of IFN-β and IL-6 by CAL-1 cells, as those genes are representative
of the dominant antiviral and pro-inflammatory responses induced when human pDCs are stimulated with “K” ODN. Most IRFs are stored in latent form in the cytoplasm and selleck inhibitor translocate to the nucleus when activated and phosphorylated [29]. To evaluate the effect of CpG ODN on the behavior of IRFs, CAL-1 cells were incubated with “K” ODN and cytoplasmic and nuclear lysates were examined by immunoblot (Fig. 2A and B and Supporting Information Fig. 1A). The first change observed was a significant rise in intranuclear IRF-5 levels within 1 h of stimulation. This was followed by a significant rise in nuclear IRF-1
at 3 h. In contrast, no translocation of IRFs 3, 7, or 8 from the cytoplasm to the nucleus was observed (Fig. 2A and B and Supporting Information Fig. 1A). find more CAL-1 cells were stimulated
for 1–9 h with “K” ODN to examine whether the accumulation of IRF-1 and IRF-5 protein in the nucleus was associated with corresponding changes in the level of mRNA expression. As seen in Figure 2C, IRF-1 and IRF-7 (a known IFN-stimulated gene) were upregulated at 6 and 9 h (Fig. 2C). When antibody against the type 1 IFN receptor (anti-IFNR) was added, this upregulation was inhibited, suggesting that the effect was dependent upon feedback by type 1 IFN. By comparison, mRNA encoding IRF-5 and IRF-8 did not vary over time. Together, Thiamine-diphosphate kinase these results suggest that “K” ODN stimulation triggers the translocation of IRF-5 from the cytoplasm to the nucleus while subsequently increasing the expression of mRNA encoding several IRFs. Members of the NF-κB transcription factor family are actively sequestered in the cytoplasm by IκB proteins. IκB proteins are phosphorylated and degraded upon TLR stimulation, resulting in the translocation of NF-κB complexes to the nucleus [30]. Although NF-κB activation has been studied in mice, data on NF-κB behavior in CpG-stimulated human cells is limited. Analysis of nuclear lysates from “K” ODN treated CAL-1 cells showed that both p50 and p65 translocated from the cytoplasm to the nucleus within 1 h (Fig. 2D). The cytoplasmic levels of these proteins did not change (Supporting Information Fig. 1B).