Fetal-maternal microchimerism in normal parous females and parous female cancer patients

Objective The prevalence of male microchimerism (MC) in parous females, nonparous females, and parous female cancer patients was examined. Materials and Methods DNA extracted from peripheral blood leukocytes and male Y-chromosomal DNA was amplified using a sensitive two-stage polymerase chain reaction technique. Controls prepared by mixing human male and female cell lines demonstrated the sensitivity of the technique to be in the range of 1 male cell per 1 million female cells. Results Findings of this study showed that the percentage of MC-positive females was highly dependent on the amount of DNA analyzed; 57% of normal parous females who bore at least one son were found to have male cells in their blood when 25 μg DNA or more from the samples was analyzed. This frequency is much higher than previous reports indicating a prevalence of 33% for normal parous females. Analysis of samples obtained from 200 parous female cancer patients revealed an incidence of 34% MC+; 7.4% of normal nonparous female controls had evidence of MC. Conclusion The long-term persistence of male cells in the maternal circulation could indicate maternal immune tolerance of paternally inherited fetal antigens. This maternal tolerance might be exploited in female patients with malignant disease to deliver immune cellular therapy from their sons.