CNTN2 and tropical spastic paraparesis: It appears that the decrease in apoptosis in HAM/TSP patients compared to ACs may be due to the continued stimulation of HTLV-1-induced cell proliferation, migration of polymorphonuclear neutrophils (PMNs) to the spinal cord, and expression of HTLV-1 virulence factors such as Tax and HBZ. In general, it appears that the decrease in apoptosis and cytotoxicity in HAM/TSP patients is due to the expression of HTLV-1 virulence factors and the continuous stimulation of PMN migration by chemokines produced by astrocytes, neurons and oligodendrocytes.