The use of polyvinylpyrrolidone as a cryoprotectant in the freezing of human lymphocytes

Polyvinylpyrrolidone (PVP), an extracellular cryophylactic agent, was used as a cryoprotectant for the preservation of human peripheral lymphocytes at ?76 °C. The recovery of lymphocytes after prolonged storage at this temperature was good, giving approximately 80% of the initial number of cells. These cells transformed in vitro, after phytohaemagglutinin (PHA) stimulation. PVP, unlike dimethyl sulphoxide (DMSO), is nontoxic and does not lyse the cells during the preparative procedures prior to the cooling stage.