Characterization of mononuclear phagocytes in patients with HAM/TSP. (A) Representative dot plots of CX3CR1 and HLA-DR expression in CD14low CD16+ cells of a ND and a HAM/TSP patient. (B) Comparison of frequencies of CX3CR1+ HLA-DR+ cells in CD14low CD16+ mononuclear phagocytes of NDs, ACs and HAM/TSP patients. The data were obtained from ten NDs, six ACs and twelve HAM/TSP patients. The CD14lowCD16+ subset of HAM/TSP patients had significantly higher levels of both CX3CR1 and HLA-DR expression, compared to NDs (p = 0.0001) and ACs (p = 0.0076) by Mann-Whitney test. The horizontal line represents the mean. (C) The frequency of CX3CR1+HLA-DR+ cells was shown to be significantly correlated with spontaneous degranulation/IFN-γ expressions in CD8+ T cells of HTLV-I-infected patients, including ACs (n = 6, opened circle) and patients with HAM/TSP (n = 12, closed circle) by simple linear regression analysis (P = 0.0004, R2 = 0.5520). (D) Localization of CX3CR1+ cells in the spinal cord of a HAM/TSP patient. Parenchyma (i) and meninges (ii) were stained with antibodies for CX3CR1 (brown). Parenchyma was stained with antibody for CX3CR1 (brown in iii), and double-stained with CX3CR1 and CD68 (red in iv). CX3CR1+ cells were positive for CD68. Magnifications, ×20. Black bar = 40 μm.