These peripheral blood mononuclear cells (PMBC's) are leukocytes isolated from whole blood and comprise of monocytes (macrophage precursors), lymphocytes (both B and T cells), and a small percentage of other immune cells, such as dendritic cells.
PMBC's must be isolated from freshly drawn blood, but can then be cryopreserved at ultra-low temperatures in liquid nitrogen to remain viable for decades with no significant changes to viability or functionality.
After a careful thawing procedure, cryopreserved (c-) PBMCs can be stimulated or treated with various immunomodulatory agents or drugs in vitro.

To preserve PBMCs at ultra-low temperatures in liquid nitrogen, dimethyl sulfoxide (DMSO) is used as a cryoprotectant to reduce the formation of ice crystals and prevent cell damage. However, DMSO is toxic to cells at higher temperature and must be washed off immediately once cells are thawed. To freeze, freshly isolated PBMCs are resuspended to 5-10 x 106 cells/mL in freezing medium containing 10-20% DMSO and 40% fetal bovine serum.