Lymphocyte migration between mutually tolerant parabiotic rats

Lymphocytes exchanged rapidly and extensively between mutually tolerant, allogeneic rats following surgical parabiosis. Tolerated allogeneic cells persisted for an extended period in parabiotic partners after separation. A rapid exchange of cells was also observed between parabiosed syngeneic pairs of normal and allograft tolerant rats. This was accompanied by early termination of the tolerant state manifested by skin graft rejection and return of specific lymphocyte alloreactivity.