DNA methylation is an epigenetic mechanism that ensures specific gene expression in different cell types.
In 2007, scientists at Epiontis GmbH (Berlin, Germany) identified genomic regions that are specifically de-methylated (i.e. no DNA methylation) in FOXP3+ regulatory T cells (Treg)1).
Regulatory T cells play important roles in fine-tuning the immune system to keep a balance between defending "foreign" and tolerating "own" cells in the body.
Epiontis scientists then developed quantitative real-time PCR (qPCR) assays to enumerate Treg cells by extracting DNA from human samples and subjecting the isolated DNA to epigenetic qPCR2).
Enumeration of Treg (and other immune cells) is important for clinicians to determine the immune status of patients with e.g. autoimmune diseases or inherited disorders of the immune system3).
Different to the current standard in clinical practice, epigenetic immune cell quantification does not require a fresh blood draw but only a drop of blood that can be dried on a filter paper or frozen and sent to a central laboratory for analysis.
Meanwhile, more than 20 immune cell type-specific epigenetic qPCR assays were established and successfully applied in more than 100 clinical studies with pharmaceutical companies.
It was successfully shown that the results obtained by epigenetic qPCR are equivalent to the results generated by flow cytometry - the current standard for enumeration of immune cells in human samples4).
Baron U, Floess S, Wieczorek G, Baumann K, Grützkau A, Dong J, Thiel A, Boeld TJ, Hoffmann P, Edinger M, Türbachova I, Hamann A, Olek S, Huehn J. DNA demethylation in the human FOXP3 locus discriminates regulatory T cells from activated FOXP3(+) conventional T cells. Eur J Immunol. 2007 Sep;37(9):2378-89. PubMed PMID: 17694575
Wieczorek G, Asemissen A, Model F, Turbachova I, Floess S, Liebenberg V, Baron U, Stauch D, Kotsch K, Pratschke J, Hamann A, Loddenkemper C, Stein H, Volk HD, Hoffmüller U, Grützkau A, Mustea A, Huehn J, Scheibenbogen C, Olek S. Quantitative DNA methylation analysis of FOXP3 as a new method for counting regulatory T cells in peripheral blood and solid tissue. Cancer Res. 2009 Jan 15;69(2):599-608. doi: 10.1158/0008-5472.CAN-08-2361. PubMed PMID: 19147574
Cepika AM, Sato Y, Liu JM, Uyeda MJ, Bacchetta R, Roncarolo MG. Tregopathies: Monogenic diseases resulting in regulatory T-cell deficiency. J Allergy Clin Immunol. 2018 Dec;142(6):1679-1695. doi: 10.1016/j.jaci.2018.10.026. Review. PubMed PMID: 30527062
Baron U, Werner J, Schildknecht K, Schulze JJ, Mulu A, Liebert UG, Sack U, Speckmann C, Gossen M, Wong RJ, Stevenson DK, Babel N, Schürmann D, Baldinger T, Bacchetta R, Grützkau A, Borte S, Olek S. Epigenetic immune cell counting in human blood samples for immunodiagnostics. Sci Transl Med. 2018 Aug 1;10(452). pii: eaan3508. doi: 10.1126/scitranslmed.aan3508. PubMed PMID: 30068569
Comprehensive list of publications describing epigenetic immune cell quantification and its applications: