Intracytoplasmic IL-10 was increased in CD4+CADM1+ T cells of HAM/TSP patients compared with CD4+CADM1- T cells of HAM/TSP patients and CD4+ T cells of healthy donors after activation (Fig 4E, S5 Fig), suggesting that IL-10 production was enhanced in HTLV-1 infected T cells. This evidence concerns the gene CADM1 and tropical spastic paraparesis.