A prospective analysis of the immunogenicity of cryopreserved nonvalved allografts used in pediatric heart surgery.

BACKGROUND The purpose of this study was to prospectively determine the immunogenicity of nonvalved allograft tissue used to repair congenital heart defects. METHODS AND RESULTS We prospectively analyzed the immune response of 11 children, 1.4 months to 10 years of age, who required nonvalved allografts to alleviate stenosis during repair of congenital heart defects. In 7 patients, pulmonary arterial grafts were used; in 3 patients, monocusp pulmonary artery grafts were used; and in 1 patient, a section of glutaraldehyde-preserved allograft pericardium was used. We measured the level of HLA panel-reactive antibody (PRA) before surgery, 1 week after, 1 month after, and 3 months after surgery. PRA was determined by the antiglobulin technique and flow cytometry. HLA class I and class II antibodies measured by either technique were negligible before and 1 week after surgery. Nine of 11 patients (82%) exhibited a significant immune response at 1 month after surgery that further increased at 3 months. The measured PRA for class I antibodies with the antiglobulin technique increased to 43+/-36% at 1 month and to 69+/-38% at 3 months after surgery. Flow cytometry class I PRA measurements were similar. Class II PRA increased to 26+/-34% at 1 month and to 41+/-36% at 3 months. Age negatively correlated with the degree of elevation of PRA, but neither allograft area nor the area indexed to patient body surface area correlated with PRA. CONCLUSIONS Cryopreserved nonvalved allografts induce a strong HLA antibody response in the majority of children.