Research ArticleIMMUNODIAGNOSTICS

Epigenetic immune cell counting in human blood samples for immunodiagnostics

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Science Translational Medicine  01 Aug 2018:
Vol. 10, Issue 452, eaan3508
DOI: 10.1126/scitranslmed.aan3508

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Counting by chromatin

Peripheral immune cell counts can be wielded to diagnose a variety of disorders. There are limitations to traditional methods such as flow cytometry, including the type of sample needed for analysis. Baron et al. took advantage of distinct immune cell epigenetic signatures and devised a real-time quantitative polymerase chain reaction (qPCR) method to perform immune cell counting without the requirement of viable cells. They examined different types of samples from healthy adults or those that were infected with HIV (and consequently had fewer CD4+ T cells). The epigenetic qPCR method correlated well with flow cytometry and could also be applied to dried blood spots to identify newborns with primary immunodeficiencies. Although it is not ready to be deployed clinically, the advantages of using epigenetic qPCR make this an intriguing approach to develop further.

Abstract

Immune cell profiles provide valuable diagnostic information for hematologic and immunologic diseases. Although it is the most widely applied analytical approach, flow cytometry is limited to liquid blood. Moreover, either analysis must be performed with fresh samples or cell integrity needs to be guaranteed during storage and transport. We developed epigenetic real-time quantitative polymerase chain reaction (qPCR) assays for analysis of human leukocyte subpopulations. After method establishment, whole blood from 25 healthy donors and 97 HIV+ patients as well as dried spots from 250 healthy newborns and 24 newborns with primary immunodeficiencies were analyzed. Concordance between flow cytometric and epigenetic data for neutrophils and B, natural killer, CD3+ T, CD8+ T, CD4+ T, and FOXP3+ regulatory T cells was evaluated, demonstrating substantial equivalence between epigenetic qPCR analysis and flow cytometry. Epigenetic qPCR achieves both relative and absolute quantifications. Applied to dried blood spots, epigenetic immune cell quantification was shown to identify newborns suffering from various primary immunodeficiencies. Using epigenetic qPCR not only provides a precise means for immune cell counting in fresh-frozen blood but also extends applicability to dried blood spots. This method could expand the ability for screening immune defects and facilitates diagnostics of unobservantly collected samples, for example, in underdeveloped areas, where logistics are major barriers to screening.

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