IMMUNOLOGICAL REACTION AND VIABILITY OF CRYOPRESERVED HOMOGRAFTS

Homograft cell viability after cryopreservation was investigated and c ytoimmunologic monitoring was performed during the early postoperative course to research possible immunologic reactions after allograft aor tic valve replacement. After cryopreservation, morphologic observation s were made, a nonradioactive cell proliferation assay was used, and p rostaglandin I-2 secretion of the remaining endothelial cells was dete rmined. Cytoimmunologic monitoring was performed daily within the firs t 3 weeks postoperatively. An increase of the activation index greater than 1 was rated as an immunologic reaction. Maintained metabolic act ivity of graft endothelial cells after cryopreservation was Confirmed by prostaglandin I-2 release (9.24 +/- 3.48 ng/cm(2) basic release and 20.1 +/- 5.76 ng/cm(2) when stimulated with 25 mu mol/L Na arachidoni c acid). Cell proliferation was indicated after graft incubation with the nonradioactive viability kit (0.27 +/- 0.9 at 450 nm). Cytoimmunol ogic examinations (n = 861) after homograft implantation showed a more intense activation in patients with ABO-incompatible grafts (activati on index 2.1 +/- 1.6, n = 16) than in those with ABO-compatible grafts (activation index 1.3 +/- 0.8, n = 17). In these groups, the duration of activation by cytoimmunologic monitoring was 2.8 +/- 1.5 days and 1.3 +/- 0.6 days, respectively (p < 0.041). No activation was observed in 8 patients after xenograft valve replacement (p < 0.01). Our data indicate that cryopreservation of homograft valves represents a cell- and tissue-protective preservation method. Postoperatively, all homogr aft valves caused immunologic reactions, which were reversible without immunosuppression treatment.