Characterization of Cell-free Dna in the Bloodstream of Normal Individuals and Those with Inflammation

Abstract

The presence of DNA in the plasma of humans has been known since 1948. The pathway that leads to the liberation of DNA from the cell still remains open to debate. . Scientists have proposed the following mechanisms underlying the presence of cell-free DNA in plasma: apoptosis, necrosis, terminal differentiation and active secretion. While the exact method of DNA liberation is still unclear, the usefulness of cell-free DNA for diagnostic purposes has not remained in question. The purpose of this study was to determine the link, if any, between the levels of cell-free DNA in patient plasma and their level of inflammation. By measuring the levels of cell-free DNA in healthy patients and patients with elevated levels of C-reactive protein, which is known to be elevated in inflammation, any link between the concentration of cell-free DNA in patient plasma and the level of inflammation could be investigated. Using the Q-TAT method of quantitation, nDNA and mtDNA were quantitated simultaneously. The results indicated a significant difference in cell-free nDNA and mtDNA concentrations in the plasma of the control and test groups (p = 0.0036). There was a slight correlation observed between cell-free nDNA and the amount of CRP present in samples, possibly explained by the role CRP plays in the complement pathway, destroying foreign bodies and damaged cells. The samples from the group with low CRP levels showed a significantly lower ratio of degradation than either the control or normal group (p value = 0.05). This shows that patients that have lower CRP have more degraded nDNA in their plasma than do patients with higher CRP levels. Gender didn't affect the concentration of nDNA or mtDNA in any of the groups.