These peripheral blood mononuclear cells (PBMC'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.
PBMC's can be cryopreserved in order 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.

Lifelines isolated PMBC's from freshly drawn blood from the first 23.000 participants during 1A Visit 2.
Freshly isolated PBMCs were resuspended to 5-10 x 10^6 cells/mL in freezing medium containing 10-20% dimethyl sulfoxide (DMSO) and 40% fetal bovine serum, and were cryopreserved at ultra-low temperatures in liquid nitrogen.
Note that DMSO, used as a cryoprotectant to reduce the formation of ice crystals and prevent cell damage, is toxic to cells at higher temperature and must be washed off immediately once cells are thawed.