Feto–Maternal Microchimerism and the Brain: Mechanisms, Neurological Implications, and Translational Perspectives

Achoimre

ABSTRACT Problem Microchimerism in the brain is a common phenomenon, where in cells cross between mother and fetus during pregnancy, and persist for decades. It has been studied primarily within reproductive immunology and transplantation medicine. The relevance of microchimerism to central nervous system biology, neurological disease, and experimental chimeric modelling has received comparatively little systematic attention. This review sought evidence across the biology of feto–maternal microchimerism, its association with neurological disease, and the emerging field of experimental chimeric brain modelling, to extrapolate a cohesive mechanistic framework. Method Research articles in reproductive immunology, neurodevelopment, and neurodegeneration were gathered to assess the potential roles of fetal microchimeric cells (FMc) in brain health and disease. By combining natural microchimerism with experimental chimeric models, a framework for understanding how nonself cells influence the maternal brain was extrapolated and critical mechanisms identified. Searches were conducted across PubMed/MEDLINE, Scopus, and Google Scholar using a dual‐concept Boolean. Results The literature reviews show that microchimeric cells cross the blood‐brain barrier (BBB), adopt neural and glial phenotypes in the maternal brain parenchyma, and exhibit injury‐responsive recruitment in preclinical models. Reciprocally, maternal microchimeric cells (MMc) are present in the offspring brain, where they have been found adopting neural and immune‐lineage phenotypes in experimental models. These findings raise the possibility that bidirectional microchimerism influences susceptibility to neurological disease, modulates neuroimmune signaling, and contributes to endogenous repair, although causal mechanisms remain unresolved. Experimental chimeric brain models have extended these principles into therapeutic contexts. Establishing the functional mechanism and directionality requires more prospective longitudinal cohort studies and transcriptional profiling at single‐cell resolution in microchimeric brain‐resident populations.