Short communication: Y chromosome microchimerism in female peripheral blood.

Male DNA of recognized fetal origin can be detected in the maternal circulation many years after delivery. It is referred to as fetal microchimerism, and is thus a possible explanation for the existence of low-level Y chromosome mosaicisms. Employing the nested polymerase chain reaction (PCR) technique, Y-specific markers were investigated in 13 cases with abnormal sex chromosome and 31 normal women. Sex-determining region Y (SRY) sequences were detected in normal women with a male child, which reflects the existence of fetal progenitor cells in the maternal circulation. This was completely absent in normal women with a female child. Individuals with the Y chromosome showed amplification for Y-specific markers. Microchimerism of Y was noted in Turner phenotype cytogenetically investigated with marker chromosome, and in an individual with XX karyotype. False positive amplifications are possible in nested PCR reactions, but the same could also be true for routine PCR. However, in the absence of any identifiable factor that could contribute to the recurrence of spurious PCR amplifications, cases of therapeutic importance must be tested at least five times. In such situations, DNA from an additional tissue should also be used for nested PCR.