Cryopreservation of whole blood samples collected in the field for a large epidemiologic study

Cryopreserved lymphocytes can be used to measure various cellular functions and are an excellent source of DNA. However, functional studies of lymphocytes have been largely limited to specimens collected in laboratory settings because of the perception that specialized equipment and handling are needed to successfully cryopreserve biospecimens. In this study, we have developed a protocol to successfully cryopreserve blood samples collected in the field as part of a pilot study of Cancer Prevention Study-3. Blood was collected in sodium heparin-containing vacutainers at six outdoor events, transported via courier to one of four different processing labs for cryopreservation, and stored in the vapor phase of liquid nitrogen. After 2 to 6 weeks of storage, the effectiveness of the protocol was evaluated by testing 30 samples for their viability, lymphocyte yield, and ability to be transformed by EBV. Although lymphocyte recovery varied considerably, all samples yielded at least 2 x 10(6) cells with at least 86% of the cells being viable. All samples were successfully transformed by EBV and yielded immortalized cell lines within 15 days of treatment with the virus. These findings indicate that whole blood samples collected in the field can be successfully cryopreserved and that the normal variation in sample handling expected in a large epidemiologic study does not compromise the quality of the cryopreserved specimens.