Effect of cryopreservation on expression of Th1 and Th2 cytokines in blood mononuclear cells from patients with different cytokine profiles, analysed with three common assays: an overall decrease of interleukin-4.

Studies on cytokine expression in blood cells are commonly performed on cryopreserved cells. Previous studies show that cryopreservation affects cytokine expression, but the findings are not consistent. This may be due to divergent effects of freezing on different cytokines, different stimuli, and different patient groups or to the use of different assays in the studies. This study was designed to investigate the effect of freezing on spontaneous, auto-antigen, allergen, and mitogen induced cytokine secretion from peripheral blood mononuclear cells from several groups of patients expressing different cytokine profiles; multiple sclerosis, atopic children, non-atopic children, and pregnant women. The expression of IFN-gamma, IL-4, IL-5, IL-9, IL-10, and IL-13 was analysed with ELISA, ELISPOT and/or real time RT-PCR. Our data provide evidence that the process of cryopreservation and thawing does affect the expression of cytokines, both at the protein and the mRNA level. Moreover, the effect varied among different cytokines, different stimuli, and different patient groups, which partly may be explained by differences in optimal freezing conditions for non-activated and activated cells. An increase of allergen and PHA stimulated IFN-gamma secretion in atopic children was found following cryopreservation, but no such increase in auto-antigen induced IFN-gamma was seen in MS-patients. The most consistent finding was that expression of IL-4 was generally decreased in spontaneous and auto-antigen/allergen induced expression in cryopreserved cells. In conclusion, this study points out the importance of investigation of the effects of freezing for each cytokine, stimuli and patient group before using frozen cells in studies of in vitro cytokine secretion.