Chinnappan, Baskaran, Kempuraj, Duraisamy, Aenlle, Kristina K et al. · Frontiers in immunology · 2026 · DOI
Researchers measured two immune proteins (IL-11 and MMP-9) in the blood of 40 ME/CFS patients and compared them to healthy controls, finding higher levels in the ME/CFS group. In the laboratory, they also showed that immune cells called mast cells release MMP-9 when exposed to a protein from Epstein-Barr virus. These are preliminary observations in one study that suggest these proteins may be associated with ME/CFS, but this does not yet establish their role in the disease.
Blood biomarkers remain scarce in ME/CFS, hindering diagnosis and research. If these proteins are eventually validated across larger populations and longitudinal studies, IL-11 and MMP-9 could become clinically useful tools. The in vitro mast cell data offers one testable hypothesis linking EBV to immune activation in ME/CFS.
This cross-sectional design does not establish that IL-11 or MMP-9 cause ME/CFS or are responsible for symptoms. It does not show whether these proteins change over time, respond to treatment, or predict disease severity. The in vitro EBV-mast cell findings are not yet replicated in patient-derived cells and do not confirm a mechanism in living patients. Small sample sizes and unknown case definition quality limit generalisability.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
The first block is for the primary paper and is the citation you should use in research work. The atlas-snapshot line only applies if you are specifically referring to this atlas’s reading of the paper on the date shown.
Primary citation
Chinnappan, Baskaran, Kempuraj, Duraisamy, Aenlle, Kristina K, Middleton, Ashley, Day, Katie S, Kothuru, Sai Puneeth, et al. (2026). Elevated serum levels of interleukin-11 and matrix metalloproteinase-9 in myalgic encephalomyelitis/chronic fatigue syndrome.. Frontiers in immunology. https://doi.org/10.3389/fimmu.2026.1827700
BibTeX
@article{mecfsatlas-chinnappan-2026-elevated-serum,
author = {Chinnappan, Baskaran and Kempuraj, Duraisamy and Aenlle, Kristina K and Middleton, Ashley and Day, Katie S and Kothuru, Sai Puneeth and Joshi, Rhitik Samir and Klimas, Nancy G and Theoharides, Theoharis C},
title = {Elevated serum levels of interleukin-11 and matrix metalloproteinase-9 in myalgic encephalomyelitis/chronic fatigue syndrome.},
journal = {Frontiers in immunology},
year = {2026},
doi = {10.3389/fimmu.2026.1827700},
note = {PubMed: 42327760},
url = {https://www.mecfsatlas.com/evidence/chinnappan-2026-elevated-serum},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-06-23. https://www.mecfsatlas.com/evidence/chinnappan-2026-elevated-serum
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