Retrospective analysis of cross-sectional and longitudinal routine clinical data examining differences in TCA (CD4/CD25, CD4/HLA-DR, CD8/CD25 & CD8/HLA-DR), β2M and neurofilament light (NfL) in plasma in ACs with high or low PVL and patients with HAM. The gene discussed is CD8A; the disease is tropical spastic paraparesis.