Figure 4.

Phenotypic analysis of human T lymphotropic virus type 1 (HTLV-1) Env380 –399 –specific CD4⁺ T cells by HLA class II tetramer staining. A, Peripheral blood mononuclear cells from 7 patients with HTLV-1–associated myelopathy/tropical spastic paraparesis (HAM/TSP) were stained with cell-surface markers of memory (CD45RA), lymph node homing (CCR7), and costimulation (CD27 and CD28). One representative result is shown. The expression of CCR7 and CD45RA in DRB1*0101/Env380-394 (DR1/Env) tetramer⁺CD4⁺ T cells indicates that the vast majority of DR1/Env tetramer⁺CD4⁺ T cells were effector memory (EM; CCR7⁻CD45RA⁻) cells. The expression of CD27 and CD28 in DR1/Env tetramer⁺CD4⁺ T cells indicated that the majority of HTLV-1–specific CD4⁺ T cells were skewed to an early (54.59%) to intermediate (IM; 28.06%) memory phenotype. B, Ex vivo phenotypic profile of HTLV-1 Env380 –399 –specific CD4⁺ T cells in 7 patients with HAM/TSP. Each dot represents the percentage of DR1/Env tetramer⁺CD4⁺ T cells that showed the indicated phenotype (early, CD28⁺CD27⁺; IM, CD28⁺CD27⁻; late, CD28⁻CD27⁻; central memory [CM], CCR7⁺CD45RA⁻; EM, CCR7⁻CD45RA⁻; and terminary differentiated effector [TDE], CCR7⁻CD45RA⁺). Means are represented by horizontal lines. C, Interferon (IFN)–γ expression in DRB1*0101/Env380-394 tetramer⁺ cells. IFN-γ was detected in tetramer⁺ cells in all 5 patients with HAM/TSP tested. More than half of DR1/Env tetramer⁺CD4⁺ T cells did not express IFN-γ (for IFN-γ⁺tetramer⁺ cells, mean ± SD of 32.47% ± 12.76% and median of 31.03%). At least 500 DR1/Env tetramer⁺CD4⁺ cells were analyzed for each sample.