MMP9 and relapsing-remitting multiple sclerosis: Interestingly, considering MMP-9 plasma levels and immunological parameters, in 116 samples from 34 RRMS patients, CD4 T-lymphocyte immune senescence and CD8 immune activation levels were positively correlated to MMP-9 plasma levels (Spearman, ρ = 0.212 and p = 0.023; Spearman, ρ = 0.184 and p = 0.048, respectively) (Fig. 5a,b).