Microchimerism of maternal origin persists into adult life

Recent studies indicate that fetal cells persist in maternal blood for deca des after pregnancy. Maternal cells are known to engraft and persist in inf ants with immunodeficiency, but whether maternal cells persist long-term in immunocompetent offspring has not specifically been investigated. We devel oped sensitive human leukocyte antigen-specific (HLA-specific) PCR assays a nd targeted nonshared maternal HLA genes to test for persistent maternal mi crochimerism in subjects with scleroderma and in healthy normal subjects. N onshared maternal-specific DNA was found in 6 of 9 scleroderma patients. In situ hybridization with double labeling for X and Y chromosome-specific se quences revealed female cells in peripheral blood samples from 2 male scler oderma patients. HLA-specific PCR also frequently revealed persistent mater nal microchimerism in healthy control subjects. The mean age of all subject s with maternal microchimerism was 28 years (range: 9-49 years). With few e xceptions, mothers of subjects with persistent maternal microchimerism were HLA incompatible with subjects for class I and class II alleles. These res ults clearly indicate that HLA-disparate maternal cells can persist in immu nocompetent offspring well into adult life. The biological significance of maternal microchimerism and whether it might contribute to autoimmune disea se requires further investigation.