Heat shock up-regulates TLR9 expression in human B cells through activation of ERK and NF-κB signal pathways

Toll-like receptors (TLRs) play a critical role in innate immunity and TLR9 is essential for CpG ODN signaling. As “dangerous signal”, heat shock may regulate immune response. However, little is known about TLRs expression and signaling after heat shock. In this study, we investigated regulation of TLR9 expression and function in human B cell line RPMI8226 by heat shock. We demonstrated that TLR9 expression was up-regulated remarkably following heat shock. Coincidently, CpG ODN stimulation significantly increased IL-6 production and up-regulated expressions of MHC I, MHC II and CD86 by heat-shocked B cells. Heat shock activated ERK and NF-κB signal pathways, and pretreatment of B cells with specific inhibitors of ERK or NF-κB signal pathways inhibited heat shock-induced up-regulation of TLR9 expression. These results demonstrated that heat shock promotes TLR9 expression and signaling through activation of ERK and NF-κB signal pathways in B cells, suggesting that heat shock might modulate host immune response by regulating TLR expression.