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 palidum (T. palidum). 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. Materials and methods. A transwell assay was applied to assess the migration of DCs. Cytokines (in-terleukin (IL)-6, IL-10, IL-12, and tumor necrosis factor alpha (TNF-alpha)) 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-alpha. 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. palidum escapes host immune clearance.