HUMAN CHIMERISM AND MICROCHIMERISM : FROM PREGNANCY BIOLOGY TO FORENSIC AND CLINICAL CHALLENGES

Abstract

The phenomenon of chimerism, wherein an individual harbors cells from two or more distinct genetic lineages, represents one of the most intriguing frontiers in modern biomedical science. Microchimerism, a specialized form involving small populations of foreign cells, arises primarily through pregnancy-related bidirectional cellular trafficking between mother and fetus. This comprehensive review examines the biological foundations of human chimerism, tracing its discovery from Schmorl's pioneering observations in 1893 through contemporary genomic-era investigations. We explore the diverse clinical implications of microchimerism, including its potential roles in autoimmune disease pathogenesis, cancer immunosurveillance, and maternal tissue regeneration. Additionally, we address the significant challenges that chimerism poses to forensic DNA identification, where mixed genetic lineages can complicate paternity testing and criminal investigations. Emerging detection technologies, from digital droplet PCR to next-generation sequencing, are discussed in the context of advancing both clinical monitoring and forensic accuracy. Understanding chimerism has profound implications for clinical medicine, forensic science, and our fundamental conception of genetic identity.