The immunogenicity of human cardiac valve allografts in vitro and in vivo

Allogeneic transplantation has become an accepted method for the replacement of diseased organs and tissues. The concept of cardiac valve transplantation for the replacement of semilunar valves was introduced by Lam et al in 1952'. In about 1960 the first human cardiac valve allografts were implanted,,3, Human donor valves have become a good alternative for other valve substitutes (porcine valve prostheses and mechanical valves) because of their superior hemodynamic performance and the absence of post-operative thrombosis and thromboembolism. Further, these valves are relatively resistant to endocarditis and recipients of human donor valves do not require anticoagulant therapy. At this moment, the valve allografts are stored at heart valve banks. In 1995, 68 heart valve banks were known world-wide'. Before the introduction of cryopreservation techniques, human valve allografts were stored at 4"C in a nutrient medium containing an antibiotic solution, with a maximum storage time of 6 weeks5 ". These antibiotic-sterilized, "fresh wet-stored" allografts showed a better medium-term (7-10 years) clinical performance than glutaraldehyde-treated human valves"'. Alternative storage techniques (freeze-drying, irradiation) resulted in a shorter long-term graft survival compared to mechanical valves"" and a higher incidence of cusp rupture". The introduction of cryopreservation procedures offered long-term storage and improved the availability of the valves.

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