Aberrant detection of phenotypic markers in chronic lymphocytic leukemia (CLL) lymphocytes following cryopreservation
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The cryopreservation of peripheral blood mononuclear cells (PBMCs) is a routine research laboratory process, enabling long-term storage of primary patient blood samples. Retrospective analysis of these samples has the potential to identify markers which may associate with prognosis and response to treatment. In order to draw valid biological conclusions from this type of analysis, it is essential to ensure that any observed changes are directly related to the pathology of the disease rather than the preservation process itself. Therefore, we have investigated 15 cell surface markers which are relevant to chronic lymphocytic leukemia (CLL) on matched fresh and thawed samples to determine the effect of cryopreservation on their detection. We found that the number of CLL cells positive for the markers CD22, CD40, CD49d, CD54, CD69 and CXCR3 was significantly decreased following cryopreservation. In addition, the MFI of 10 of the 15 markers significantly changed following cryopreservation. These findings demonstrate that care must be taken when interpreting this type of analysis on thawed samples.