Cross-species bone marrow transplantation: evidence for recognition of skin-specific antigens across a species barrier (rat----mouse).

We have developed a model to study cross-species bone marrow transplantation and the associated donor-specific transplantation tolerance induced using fully xenogeneic chimeras. Reconstitution of lethally irradiated B10 mice with untreated F344 rat bone marrow cells results in fully xenogeneic chimerism (F344 rat----B10 mouse). Survival of recipients is excellent (greater than 80% at 100 days) and stable rat lymphoid and multilineage chimerism are present throughout the life of the chimeras. Recipients are specifically tolerant to donor-type skin xenografts yet are competent to reject major histocompatibility complex (MHC)--disparate third party strain rat xenografts. Although prolonged, donor-specific skin xenografts underwent chronic rejection which had its onset at approximately 40 days following skin graft placement. We have now examined these chimeras by serial flow cytometry typing to determine whether this is due to skin-specific antigens expressed on skin, but not on the bone marrow elements to which the chimeras were rendered tolerant. In all animals examined, lymphopoietic chimerism persisted unchanged even after the onset of inflammation in the grafts, suggesting the presence of skin specific antigens. This model may provide a method to study tissue and organ specific antigens recognized across a species barrier.