The role of the 47-kDa membrane lipoprotein of Treponema pallidum in promoting maturation of peripheral blood monocyte-derived dendritic cells without enhancing C-C chemokine receptor type 7-mediated dendritic cell migration

BACKGROUND: The 47-kDa membrane lipoprotein (Tp47) is the most representative membrane protein of Treponema pallidum (T. pallidum). Dendritic cells (DCs) are the most potent professional antigen-presenting cells (APCs) that connect innate and acquired immunity. The regulatory role of Tp47 on DCs remains unclear. OBJECTIVES: To evaluate the effects of Tp47 on DC maturation and migration, and research the changes of the main chemokine C-C chemokine receptor type 7 (CCR7) involved in DC migration. MATERIAL AND METHODS: A transwell assay was applied to assess the migration of DCs. Cytokines (interleukin (IL)-6, IL-10, IL-12, and tumor necrosis factor alpha (TNF-α)) in the supernatants were measured using enzyme-linked immunosorbent assay (ELISA), and the expression of cell surface markers (CD80, CD86, CD40, and human leukocyte antigen (HLA)-DR) and CCR7 was assessed using flow cytometry. The expression of CCR7 in DCs was analyzed using quantitative real-time polymerase chain reaction (qRT-PCR). RESULTS: The Tp47 promoted DC phenotypic maturation, such as increased CD40, CD80, CD86, and HLA-DR expression, as well as DC functional maturation, thus stimulating DCs to secrete inflammatory cytokines, including IL-6, IL-10, IL-12, and TNF-α. At the same time, Tp47 did not enhance DC migration and did not increase the expression of CCR7. CONCLUSIONS: The Tp47 promoted the maturation of DCs while not enhancing CCR7-mediated DC migration ability. This may be one of the mechanisms by which T. pallidum escapes host immune clearance.