Chimeras are organisms that coexist genetically different cell or tissue. Owen (R. Owen) showed that dizygotic cow twins red blood cells represent a mixture of cells both of the individual. It was shown that "erythrocyte mosaic" is a consequence of the establishment of common placental circulation in developing embryos. Cell chimerism saved all his life and is accompanied by mutual immunological tolerance. Skin flaps, transplanted from one calf-chimeras another, prizivaut.
In experimental conditions cell chimerism most successfully reproduced in irradiated animals. Ionizing radiation, suppressing transplantation immunity successful transplant of genetically alien blood-forming tissue. Successful engraftment of these tissues prevents the death of the recipient of radiation illness and leads to radiation of chimeras. Hematopoietic tissue and blood radiation chimeras presents lashes two genotypes donor and recipient. They have successfully prizivaut skin, kidneys, and other organs of the donor. Unfortunately, most of radiation chimeras nonviable due to the development of immunological conflict due to reactions "to the transplant against the host and host versus graft" (see Radiation immunology).