The Presence of Immune Stimulatory Cells in Fresh and Cryopreserved Donor Aortic and Pulmonary Valve Allografts
Frans B. S. Oei MD, Alexander P. A. Stegmann PhD, Frieda van der Ham BSc, Pieter E. Zondervan MD, Len M. B. Vaessen PhD, Carla C. Baan PhD, Willem Weimar MD, Ad J. J. C. Bogers MD

Implantation of human donor valves has been associated with a donor-specific humoral and cellular immune response. However, the cellular basis of the immunogenicity of the aortic and pulmonary valve allograft is unclear. By using immunohistochemical staining, the presence and distribution of cells with known immune stimulatory capacity was investigated in valve allografts obtained from two different donor populations. The effect of cryopreservation was studied by symmetric division of valve tissue. Endothelial cells were equally present in the aortic and pulmonary valves, while mononuclear cells were more often found in aortic grafts. No difference in cellular distribution was observed between the donor groups. Cryopreservation reduced the cellularity in the valve matrix, but the endothelial lining in the vasa vasorum was not affected. Dendritic, natural killer and B cells were absent from the grafts. In conclusion, fresh and cryopreserved valve allografts contains cells with proven immune stimulatory capacity.