Interestingly, the ratio of CD86:CD80 expression in B cells but not in T cells correlated negatively to disease severity in HAM/TSP patients (r = −0.50, n = 18) (Additional file 1: Figure S1), implying a possible antagonism between the two costimulatory molecules, as previously suggested by Genç et al. in MS patients [33]. Here, CD80 is linked to tropical spastic paraparesis.