CD4 and tropical spastic paraparesis: These results indicated that peripheral blood CD4+ T cells of HAM/TSP patients, particularly HTLV-1-infected CD4+ T cells, have heightened transmigrating activity based on the induction of RBM disruption, suggesting that the character of the heightened transmigrating activity of HTLV-1-infected CD4+ T cells through the vascular basement membrane acquires the ability to accumulate in the tissues and is consistent with the findings that HTLV-1 provirus accumulates in CSF in HAM/TSP patients compared to HTLV-1 asymptomatic carriers as earlier described [17,18].