[Critical role of rate previous freezing on the liberation of heat of fusion the preservation of hematopoietic cell lines].

71 bags of bone marrow cryopreserved and stored for periods up to 2 years, were thawed and CFUc recoveries were studied in relation to the rate of freezing following the heat of fusion. Excellent CFUc recoveries (greater than 50%) were obtained in all cases (11/11) for freezing rates smaller than 5 dgC/mn, whereas freezing rates greater than 10 dgC/mn produced poor recoveries in 78% of the cases (4/18). Intermediate freezing rates (5 less than 0 less than 10) resulted in intermediate yields of CFUc, with good recoveries in only 45% of the cases (19/42). These results indicate that CFUc recoveries and subsequently the kinetics of autologous engraftment following the infusion of cryopreserved marrow, which are already known to be related both to the freezing rate before the heat of fusion and the duration of the phase transition period, are also related to this new parameter, which should be carefully monitored during the freezing procedure.