As shown in Fig. 1a and b, CCL1 mRNA was preferentially expressed in HTLV-1-infected human T-cell lines derived from patients with HAM/TSP (4 out of 4 tested), compared with HTLV-1-transformed T-cell lines (1 out of 3) and ATL cell lines (1 out of 4). Here, CCL1 is linked to tropical spastic paraparesis.