Increased responsiveness to TLR2 and TLR4 ligands during dimethylsulfoxide-induced neutrophil-like differentiation of HL-60 myeloid leukemia cells

Neutrophils express functional toll-like receptor2 (TLR2) and 4 (TLR4) that are crucial for the production of inflammatory cytokines. Here, we show that dimethylsulfoxide-induced neutrophil-like differentiation of promyelocytic HL-60 cells (dHL-60) results in cells that respond to TLR2 and TLR4 ligands similarly to primary neutrophils. Consistent with the increased responsiveness of the cells to TLR2 ligand, the TLR2 gene was strongly up-regulated in dHL-60 cells. On the other hand, increased surface expression of LPS receptor complex, TLR4/MD2/CD14, was observed without affecting TLR4 gene expression. Thus, the data demonstrate a higher responsiveness of dHL-60 cells to TLR2 and TLR4 ligands because of increased TLR2 and MD2/CD14 gene expression.