chim-, chimer- +

(Greek: khimaira, fabled monster; unreal, fantastic, imaginary, fanciful, unrealistic; however, in medical and other scientific fields, characterized by two or more genetically distinct cell types in one organism)

tetraparental chimera
An animal derived or coming from four parents.

This is achieved by fusing two allogeneic early blastocysts (mammalian embryo at the stage when it is implanted in the wall of the womb) and reimplanting the fusion product into the uterus.

Tetraparental chimeras allow the relative effects of genetic constitution and early environment of the development of immunological tolerance and reactivity to be studied.