Test for cryopreservation efficiency of human acute myelogenous leukaemia cells relevant to clinical requirements

Cryopreserved AML cells from eight patients when thawed retained radioactive chromium better when they were labelled with the chromium after they had first been grown in short-term in vitro culture to establish proliferative cell populations. Such labelled cells are required for immunological studies of patients with acute leukaemia, so the ability to proliferate is a new test, more relevant to immunology than other available methods, for designing optimum cryopreservation conditions for these AML cells.Fifty-six populations of cryopreserved AML cells (from 53 patients) were cultured in vitro, and the growth pattern of the cell populations fell into three classes: (i) rapid death of some of the cells followed by proliferative growth and an increase in cell number (14 populations); (ii) cultures in which the cell number remained constant after an initial fall (6 populations), and (iii) rapid death of all the cells (36 populations). Although morphological studies showed maturation of some of the leukaemia blast cells into polymorphs during proliferative culture, leukaemia cells persisted in all cultures. In addition, in two cases it was shown that cells from the cultures had the same karyo-type abnormalities as those found in the donor's bone marrow and so it was concluded that the proliferating cells were of leukaemic origin rather than from normal cells.Using the proliferative capacity of AML cells from nine patients as a test of factors influencing cryopreservation efficiency, it was shown that the longer AML cells were kept in DMSO (5, 7.5, and 10%) for periods of up to 120 min prior to controlled slow freezing (+4 to ?30 °C at l °C/min), the poorer was their capacity to grow.