CXCL9 and tropical spastic paraparesis: Many types of cells are able to produce chemokines and their levels are variable, even in healthy subjects, therefore future studies performed in vitro and ex vivo should be carried out to understand whether HTLV-1 patients with different dermatological lesions indeed have a distinct chemokine secretion profile and also comparing the chemokine profile of HAM/TSP specially regarding their serum levels of CXCL9.