Single-born marmosets without hemopoietic chimerism: naturally occurring and induced.

Marmosets have a high frequency of fraternal twinning, and placental vascular anastomoses between the twin fetuses invariably lead to hemopoietic chimerism. The occasional finding of chimerism in single-born marmosets suggested that in a twin pregnancy one fetus had undergone resorption after contributing hemopoietic stem cells to its twin. In this study non-chimeric single-born marmosets were produced by fallopian tube ligation or surgical relocation of one ovary in breeding females. Further, in an examination of hemopoietic cells from over 50 single-born young from nonoperated females, chimerism occurred less frequently than what one would expect if resorption of a co-twin had occurred after a functional anastomosis had been established.