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August 2014


Background The activation of mononuclear phagocytes (MPs), including monocytes, macrophages and dendritic cells, contributes to central nervous system inflammation in various neurological diseases. In HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP), MPs are reservoirs of HTLV-I, and induce proinflammatory cytokines and excess T cell responses. The virus-infected or activated MPs may play a role in immuneregulation and disease progression in patients with HTLV-I-associated neurological diseases.

Results Phenotypic analysis of CD14+ monocytes in HAM/TSP patients demonstrated high expression of CX3CR1 and HLA-DR in CD14lowCD16+ monocytes, compared to healthy normal donors (NDs) and asymptomatic carriers (ACs), and the production of TNF-α and IL-1β in cultured CD14+ cells of HAM/TSP patients. CD14+ cells of HAM/TSP patients also showed acceleration of HTLV-I Tax expression in CD4+ T cells. Minocycline, an inhibitor of activated MPs, decreased TNF-α expression in CD14+ cells and IL-1β release in PBMCs of HAM/TSP patients. Minocycline significantly inhibited spontaneous lymphoproliferation and degranulation/IFN-γ expression in CD8+ T cells of HAM/TSP patients. Treatment of minocycline also inhibited IFN-γ expression in CD8+ T cells of HAM/TSP patients after Tax11-19 stimulation and downregulated MHC class I expression in CD14+ cells.

Conclusion These results demonstrate that minocycline directly inhibits the activated MPs and that the downregulation of MP function can modulate CD8+ T cells function in HAM/TSP patients. It is suggested that activated MPs may be a therapeutic target for clinical intervention in HAM/TSP.


© 2012 Enose-Akahata et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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