Fletcher, Mary A, Zeng, Xiao R, Maher, Kevin et al. · PloS one · 2010 · DOI
This study tested whether two immune system markers could reliably identify ME/CFS patients. Researchers measured natural killer (NK) cell function—a type of immune cell that fights infections—and CD26, a protein found on immune cells. They found that ME/CFS patients had lower NK cell function and different patterns of CD26 compared to healthy people, suggesting these markers could potentially help diagnose the condition.
Identifying reliable biomarkers for ME/CFS could improve diagnosis and help researchers understand the disease's biological mechanisms, particularly regarding immune dysfunction and possible infectious triggers. This work supports the hypothesis that immune dysregulation—specifically abnormal NK cell function and CD26 expression—plays a central role in ME/CFS pathophysiology.
This study does not prove that these biomarkers cause ME/CFS or that correcting them will cure the disease. The findings do not establish diagnostic cutoffs suitable for clinical practice, nor do they demonstrate prognostic value or predictive utility for treatment response. The lack of correlation between NKCC and CD26 does not clarify whether these represent independent disease mechanisms or parallel consequences of an unmeasured underlying cause.
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 →
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Primary citation
Fletcher, Mary A, Zeng, Xiao R, Maher, Kevin, Levis, Silvina, Hurwitz, Barry, Antoni, Michael, et al. (2010). Biomarkers in chronic fatigue syndrome: evaluation of natural killer cell function and dipeptidyl peptidase IV/CD26.. PloS one. https://doi.org/10.1371/journal.pone.0010817
BibTeX
@article{mecfsatlas-fletcher-2010-biomarkers-chronic,
author = {Fletcher, Mary A and Zeng, Xiao R and Maher, Kevin and Levis, Silvina and Hurwitz, Barry and Antoni, Michael and Broderick, Gordon and Klimas, Nancy G},
title = {Biomarkers in chronic fatigue syndrome: evaluation of natural killer cell function and dipeptidyl peptidase IV/CD26.},
journal = {PloS one},
year = {2010},
doi = {10.1371/journal.pone.0010817},
note = {PubMed: 20520837},
url = {https://www.mecfsatlas.com/evidence/fletcher-2010-biomarkers-chronic},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-26. https://www.mecfsatlas.com/evidence/fletcher-2010-biomarkers-chronic
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