Expression of TLR4 in dental pulp cells. Immunohistochemistry for TLR4 gene expression analysis (A, C, E, G) using a non-specific IgG as control (B, D, F, H). TLR4 was observed in the dental pulp stem cells (DPSC), human dental pulp fibroblasts (HDPF), rat odontoblast-like cells (MDPC-23), and mouse macrophages (control).