PRESERVATION OF IMMUNOLOGICAL AND COLONY-FORMING CAPACITIES OF LONG-TERM (15 YEARS) CRYOPRESERVED CORD-BLOOD CELLS

Background, Cryopreserved cord blood may be stored for decades before being used for allogeneic stem cell transplantation. Little is known a bout the effect of long-term cryopreservation in liquid nitrogen on th e viability and function of cord blood cells. We examined the recovery , viability, clonogenic capacity, and T-cell reactivity to HLA alloant igens of cord blood samples cryopreserved up to 15 years. Methods. Pro genitor cell recoveries were studied by (colony-forming unit-granulocy te-macrophage) clonogenic assays from 18 cord blood samples short-term frozen for 2-8 weeks and from 8 samples cryopreserved for 15 years. P roliferative and cytotoxic responses against HLA antigens of thawed co rd blood mononuclear cells after short-term or long-term cryopreservat ion were tested in standard mixed lymphocyte cultures and cell-mediate d lympholysis assays. Results. After thawing, the mononuclear cell rec overy from long-term frozen cord blood low-density fractions averaged 80% (range, 64% to 92%). The presented data show that long-term frozen cord blood cells keep their clonogenic potential. No damaging effect was seen on the proliferative and cytotoxic capacities of long-term fr ozen cord blood T cells. Conclusions. The results support the possibil ity of long-term storage of progenitor cells from umbilical cord blood for future bone marrow reconstitution.