chimerism

The state of being a chimera; the presence in an animal of cells of different origin, e.g. XX/XY chimerism.

• blood c. — twins that have a common circulation develop immune tolerance. Each of them is then a chimera. When the twins are of opposite sex, the female twin may be a freemartin. Sterilization of the female is brought about by the transfer of H-Y antigen to the female gonad.