Figure 5.

Proposed model of microchimerism-induced tolerance to alloantigens. During fetal life, maternal stem cells can cross placenta and engraft into different organs of offspring. They are immune-privileged and lack MHC expression. Thus they can avoid immune mediated rejection. However, the lineage⁺ cells differentiated from the stem cells can express MHC class I/II and can be detected and killed by NIMA-specific T cells of the offspring. These effector T cells can be blocked by NIMA-specific regulatory T cells generated via oral exposure to NIMA and liver MMc engraftment during nursing.