The causes of degenerative changes in allograft cardiac valves are not well known to this day. Today's preserved allografts possess highly viable endothelial cells and degeneration of allografts can be facilitated by immune reaction which may be
mediated by these viable cells. To test the antigenicity of endothelial cells, pieces from aortic wall were obtained from fresh and cryo-preserved rat allograft. Timings of sampling were prior to sterilization, after sterilization, after 1, 2, 7,
14
days of fresh preservation and cryopreservation. Endothelial cells were tested by immunohistochemical methods using monoclonal antibodies to MHC class I(MRC OX-18), class II(MRC OX-6) and ICAM-l antigens. After transplantation of each group of
aortic
allograft at the subcutaneous layers of rats, population of CD4+ T cell and CD8+ T cell were analyzed with monoclonal antibodies after 1, 2, 3, 4, 6 and 8 weeks.
MHC class I expression was 23.95% before preservation and increased to 35.53~48.08% after preservation(p=0.0183). MHC Class II expression was 9.72% before preservation and 10.13~13.30% after preservation(P=0.1599). ICAM-l expression was 15.02%
before
preservation and increased to 19.85~35.33% after preservation(P=0.001).
The proportin of CD4+ T-cell was 42.13% before transplantation. And this was 49.23~36.8% after transplantation in No treat group (p=0.955), decreased to 29.56~32.80% in other group(p=0.0001~0.008). In all the groups, the proportion of CD8+ T-cell
increased from 25.57% before transplantation to 42.32~58.92% after transp'antation(p=0.0001~0.0002). The CD4+/CD8+ ratio decreased from 1.22~2.28 at first week to 0.47~0.95 at eighth week(p=0.0001)
The results revealed that the expression of MHC class I and ICAM-l in aortic allograft endothelium were increased but that of MHC class II were not changed, despite the different method of preservation. During 8 weeks after transplantation of
aortic
allograft, the subpopulations of CD4+ T cell were not changed or only slightly decreased but those of CD8+ T cell were progressively increased.
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