A Chick Embryo Model for the Study of Allograft Rejection 1

Discussion and Summary The data presented here indicate that fragments of heart tissue from outbred chick embryo donors of 5–14 days of incubation may be successfully grafted to the CAM of chick embryos which are 8 days of incubation or older. The cardiac tissue becomes vascularized, continues to grow and continues contractions which rhythmically expel blood from the vascular channels. The CAM of embryos younger than 13 days of incubation do not accept the grafts. Rejection of the grafts in more than 90% of the embryos can be effected by administration of peripheral blood lymphoid cells from outbred chickens. Washed cells obtained from the spleens of chickens can also bring about graft rejection but experiments comparing lymphoid cells from the spleen and the blood of the same chicken showed that the blood lymphoid cells are consistrntly more effective in producing rejection The incidence of rejection reactions is directly related to the cell dosage. Conversely the number of surviving. rhythmically contracting grafts is indirectly related to the cell dosage. Histological studies showed that massive cellular ac:cumulations occur in the celltreated grafts. These are associated with destruction of most or all of the cardiac fibers by day 10 following administration of the cells.