Antigenicity of fresh and cryopreserved rat valve allografts

Aortic valve allografts have demonstrated excellent clinical performance, but the importance of antigenic differences between donor and recipient is largely unknown. To determine the antigenicity of aortic valve grafts, rat aortic valves with a short portion of thoracic aorta were transplanted into the abdominal aorta of recipient rats. Valves were used immediately after harvest (fresh) or following cryopreservation. Three weeks after this procedure, the recipient rats received a skin graft from a rat of a strain syngeneic to that of the aortic valve donor. Additional groups of rats were subjected to sham operation (sham) followed three weeks later by skin grafting. Recipient rats were of the Lewis strain. Donor rats were of the Lewis, F344 (weakly allogeneic, RT1-compatible, non-RT1-incompatible), LBN F1 (moderately allogeneic, one-haplotype-identical and one-haplotype-incompatible at both the RT1 and non-RT1 loci), or BN (strongly allogeneic, RT1 and non-RT1-incompatible) strain. Time to skin graft rejection was measured. Among rats receiving the F344 grafts, the time to skin graft rejection (mean +/- SD) was sham: 9.1 +/- 1.0 days, fresh: 7.1 +/- 1.2 days, cryopreserved: 6.9 +/- 0.7 days. Among rats receiving the LBN F1 grafts, the corresponding times were sham: 7.8 +/- 0.8 days, fresh: 5.6 +/- 0.5 days, cryopreserved: 5.4 +/- 0.5 days. Among rats receiving the BN grafts, the corresponding times were sham: 7.1 +/- 0.3, fresh: 4.5 +/- 1.0 days, and cryopreserved: 4.3 +/- 0.7 days. Significant differences (P less than 0.05) existed between sham and fresh and between sham and cryopreserved, but not between fresh and cryopreserved. Significant differences (P less than 0.05) also existed between each histocompatibility grouping. It is concluded that aortic valve allografts in rats are antigenic and produce recipient sensitization. Cryopreservation does not diminish this sensitization. The degree of antigenicity is related to the degree of histoincompatibility between donor and recipient. Both RT1 and non-RT1 antigens appear to play a role in this process.