Elevated serum levels of interleukin-11 and matrix metalloproteinase-9 in myalgic encephalomyelitis/chronic fatigue syndrome.

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a disease of unknown etiology associated with chronic severe fatigue and neurological symptoms, including dizziness, sleep disturbances, cognitive impairment and pain. There are no reliable blood biomarkers available for ME/CFS, possibly due to the lack of specific pathogenesis, even though Epstein-Barr Virus (EBV) has been suspected. We quantified the levels of interleukin-11 (IL-11) in the serum of female ME/CFS patients (n = 40; mean age 51 years) and age- and gender-matched healthy control subjects (n = 38; mean age 43), as well as matrix metalloproteinase-9 (MMP-9) in ME/CFS patients (n = 18; mean age 57 years old) and healthy control subjects (n = 18; mean age 53 years old), using an enzyme-linked immunosorbent assay (ELISA). We hypothesized that mast cells (MC) stimulated by EBV may be involved. MC are unique tissue immune cells that have been implicated in ME/CFS. MC were grown from human umbilical cord blood CD34+ stem cells in vitro and incubated with recombinant (rEBV) protein, following which the release of MMP-9 was assayed in the cell culture supernatant media by ELISA. There was a significant increase in serum levels of IL-11 and MMP-9 in ME/CFS patients compared to control subjects. MCs stimulated by rEBV protein released a high amount of MMP-9 compared to control cells. In conclusion, IL-11, MMP-9 and MCs may be involved in ME/CFS individuals.