Cell-free DNA as a Clinical Indicator in Maternal Blood

I. Thehistoryof cell-freeDNA(cfDNA)discovery Cell-free DNA (cfDNA) was discovered in 1948 by Mandel and Mëtais, who observed the existence of free nucleic acids in plasma (1). They found free DNA and RNA in the plasma of healthy as well as unhealthy people. In 1965, Bendich et al. suggested that cfDNA from cancer tissue could be involved in cancer metastasis. In 1966, Tan et al. found an enormous amount of cfDNA in the blood of patients with systemic lupus erythematosus (2). Technological limitations delayed the confirmation of use of cfDNA as an indicator of diseases. Figure 1 shows the presence of cfDNA in blood (3). II. Definition of cfDNA cfDNA means DNA fragments present outside the nucleus of a cell. cfDNA is mainly produced by an apoptotic or necrotic process. The fragments are also present in body fluids, so they can be considered as biological markers of pathological states (4). cfDNA has also been discovered in human seminal fluid (5).