Expression and function of TR7/8 in monocytes and macrophages

We have studies the response of Mo subsets to the TLR 7/8 ligand R848 (Resiquimod). Whole blood stimulation demonstrated a 2 fold higher level of TNF protein in the CD14+CD16+ Mo as measured by intracellular cytokine staining (p < 0.001). CD14+CD16+ Mo expressed 2 fold more of TLR7 protein and 1.3 fold less of TLR8 protein than CD14++ Mo. ssRNA that represents the natural ligand for human TLR8 induced lower TNF production in CD14+CD16+ Mo. Taken together, these data raise the possibility that the higher TLR7 protein level is essential in determining higher TNF production induced by R848 in CD14+CD16+ Mo. Little is known about the differentiation of CD14+CD16+ into macrophages (Mf). Therefore, we investigated the ability of Mo subsets cultured with M-CSF in vitro for 3 days to generate monocytes-derived macrophages (MDM). CD14+CD16+ MDM expressed higher levels of HLA-DR and TLR7 protein and lower levels of CD14 and TLR8 protein compared to CD14++ MDM while levels of CD68 and CD16 were similar. R848 induced TNF production in both MDM subsets. We analysed Mo subsets of patients with recurrent warts for TNF expression in response to R848. Compared with the normal donors, Mo subsets from patients with recurrent warts did not respond to R848 at 100ng/ml whereas at 1 mug/ml CD14+CD16+ Mo produced TNF but at a significantly lower level compared to controls (p < 0.005). These data indicate that the failure to respond to TLR7 ligand may contribute to the patients' susceptibility to recurrent warts.