Cryopreservation of human monocytes

Monocytes were isolated from human peripheral blood by Ficoll-Isopaque density-gradient centrifugation and adherence to glass. These cells were then frozen according to an automatically controlled cooling program and stored in liquid nitrogen.After the freezing, thawing and washing, 63% of the cells present before cryopreservation were recovered. Over 95% of the recovered cells excluded trypan blue. Storage at ?196 °C did not alter the percentage of monocytes (70–80%) in the supensions.Although the percentage of cells that formed rosettes with erythrocytes sensitized with IgG antibodies (EAIgG) was unaltered after freezing, formation of EA rosettes was more readily inhibited by free IgG. The capacity of monocytes to lyse EAIgG was not influenced by cryopreservation, in contrast with their potency to phagocytize zymosan particles, which was decreased. The chemotactic response toward casein was also diminished after freezing. There was no significant difference in reactivity between monocytes frozen for a short time (2–15 hr) and those frozen for a longer period (more than 3 months).Electron microscopic examination showed alterations in the mitochondrial structure of the frozen cells.