Background: Since the development of techniques to cultivate DC from peripheral blood, there has been a great deal of interest in the use of these cells in immunotherapeutic strategies. In a clinical setting, delays often occur between when blood is drawn and when it is processed. We therefore investigated the effect of overnight storage on the yield, morphology and phenotype of DC cultured from the peripheral blood of healthy volunteers.
Method: Blood was processed either immediately, or after storage for 24 h in the fridge (4 degrees C) or at room temperature (RT, 20 degrees C). Samples were compared for starting cell number, DC yield and characteristics (morphology and phenotype).
Results: The number of PBMC that could be obtained was significantly lower from the refrigerated samples compared with both the freshly processed sample and that stored at RT. Samples processed after overnight storage at RT yielded cells morphologically identical to DC cultured from freshly processed samples. Only when samples were both stored and processed cold did the cultured cells not have typical DC morphology. DC cultured from the refrigerated samples showed a significant reduction in MHC II expression compared with samples processed fresh or stored at RT. This expression increased slightly when the sample was first warmed. Total DC yield and the percentage yield of cultured DC was not significantly different for any of the groups.
Discussion: We conclude that, if immediate processing of blood for in vitro generation of DC is not possible, samples should be stored at room temperature (approximately 20 degrees C).