chimerism

Chimerism is a situation when there is one body with two cell populations. A chimera a single organism that is composed of two or more different populations of genetically distinct cells that originated from different zygotes involved in sexual reproduction.

This condition is either inherited, or it is acquired through the infusion of allogeneic hematopoietic cells during transplantation or transfusion. In nonidentical twins, chimerism occurs by means of blood-vessel anastomoses. The likelihood of offspring being a chimera is increased if it is created via in vitro fertilization. Chimeras can often breed, but the fertility and type of offspring depends on which cell line gave rise to the ovaries or testes; varying degrees of intersexuality may result if one set of cells is genetically female and another genetically male.

A special case is microchimerism, which occurs most frequently by colonization of mother body by cells of the body of the child (or vice versa).