CCL4 and myalgic encephalomeyelitis/chronic fatigue syndrome: Interestingly, in EV samples from the control group, 3 cytokines strongly positively correlated with the 30-130 nm extracellular vesicle population (MIP-1β, MIP-3β and IL-2, Additional file 2: Fig. 2a–c) but not in the ME/CFS group.