This is an interesting question because many groups use fresh PBMCs due to concerns about the quality of cryopreserved PBMCs. We routinely use a 10% DMSO with 10% FBS protocol and obtain 50-65% PBMC viability by Trypan Blue exclusion. We use these cells in one way mixed lymphocyte cultures and they behave in a manner similar to fresh PBMCs. The protocol suggested by Andrei incorporates using human serum albumin, a thorough thawing protocol and slow dilution of the cryoprotectant solution. These are all excellent methods suggested by the literature for minimizing damage to cryopreserved PBMCs that are not necessarily needed for most of the relatively hardy cell lines that we work with. We will give this protocol a comparison trial next time we freeze back a batch of PBMCs.

You can use a criopreservation medium that behaves well on CD34 + cells.

5% DMSO or 10% DMSO with either 20% of FBS. Another solution consists in 70% FBS when Iscove's modified Dulbecco's medium consists of not more than 10% of DMSO.