Effect of PBMC shipment and storage conditions on ELISpot activity

Abstract

INTRODUCTION: Cellular immune response is often evaluated on frozen Peripheral Blood Mononuclear Cells (PBMC). Here, we evaluate the effect of shipping and storage conditions on PBMC viability and functional response using ELISpot assay.METHODS: Cryopreserved human PBMC were evaluated after overnight placement on dry ice and subsequent storage at −80oC, −20°C, in LN2 and on dry ice for up to 6 months. Cell count and viability was measured at time of thaw and after 24 hour rest. ELISpot assays were performed using huIFN‐γ ELISpot Kit (SeraCare) after stimulation with PHA, CMV and CEF peptide pools.RESULTS: Cells stored overnight on dry ice showed no significant decrease in viability at thaw and post rest. Cells stored at −20°C were not suitable for ELISpot assay. Cells stored on dry ice, at −80°C or in LN2 for 6 month demonstrated 92–93% viability upon thaw and 80–86% after 24 hr rest. The control cells remained 90% viable both post thaw and post rest. ELISpot responses of cells stored at −80°C or in LN2 for 6 month, or cells stored on dry ice for 4 weeks were comparable to control.CONCLUSIONS: The PBMC shipped in dry ice can be stored at −80°C for up to 6 months or on dry ice for 4 weeks with no appreciable loss of viability or functionality. Therefore, the use of PBMC for ELISpot proficiency testing is possible even in laboratories which lack ultra‐cold storage facilities.SUPPORT: This work was supported by NIAID contract NO1‐AI‐85341.