Evidence from cultured leucocytes of blood cell chimerism in ex-parabiotic frogs.

Postmetamorphic diploid and triploid frogs that had earlier been joined in parabiotic union from embryonic life until metamorphosis were each found to be chimeric with respect to their blood cells, as revealed in chromosome preparations of cultured leucocytes. Blood cells precursorsmost likely were interchanged when the ex-parabionts shared a common circulation in embryonic life,and the exchanged precursor cells apparently homed in the hematopoietic tissues of the hosts. The tolerance which exparabiotic pairs of frogs exhibit toward grafts of each other's skin is attributable to the blood cell chimerism.