Microchimerism in F1 backcross offspring. (A) The left panel shows a representative PCR curve showing standard and negative controls. The right panel shows H2D^d standard curve. Each data point is shown as mean ± range of values. qPCR was performed with BDF₁ DNA diluted into B6 DNA in different concentrations. B6 DNA and blank (DNAase-free water) were used as negative controls. Primers and probe specific for maternal H2D^d were used to detect maternal DNA. A standard curve was made from 15 independent experiments. (B) Histogram showing variability in the levels of Mc in NIMA^d-exposed versus control F1 backcross mice (standard breeding), plotted by percentage of offspring with indicated number of organs positive by H2D^d qPCR. (C) Top panel shows tissue distribution of Mc in different organs of NIMA^d-exposed (n = 41 [*n = 12 for blood only]) and NIPA^d (n = 16) control mice expressed as H2D^d gene equivalents (GEq) per 10⁵ cells. The y-axis shows estimated GEq per 10⁵ cells. Bottom panel shows GFP Mc in different organs of NIMA^d NIMA^GFP-exposed (n = 11) and NIPA^d NIPA^GFP control (n = 6) mice. (D) Summary of tissue distribution data in panel C expressed as a percentage of NIMA-exposed mice with detectable levels of Mc in each organ.