[Organ tolerance and incomplete bone marrow chimera in dogs]

Cyclophosphamide-induced chimeras develop organ tolerance as do radiation chimeras, as long as hemopoietic cells of donor origin are detectable, independent of the degree of chimerism (n = 7). 4 of 7 dogs with reversion of chimerism rejected their kidney grafts within 11 to 29 days. Three of them, however, retained their kidney grafts permanently indicating that a transient chimerism of a few months duration may be sufficient for induction of tolerance to marrow donor organs in Cy-chimeras. The results suggest that the reversion of chimerism in Cy-chimeras may be due to different mechanisms either immunological rejection or a non-immunological substitution of the grafted marrow by the host's own hemopoiesis.