Paraformaldehyde fixation of hematopoietic cells for quantitative flow cytometry (FACS) analysis

The objective of this study was to find a simple method to preserve cells for subsequent flow cytometry (FACS) analysis. We determined that fixation in 1% paraformaldehyde—0.85% saline solution did not significantly alter the Coulter volume, light scatter or fluorescence properties of the cells. This method was suitable for all cell types analyzed, including mouse, human and rat lymphoid cells, erythrocytes and transformed cell lines. Furthermore, fixed cells, previously stained with fluorescein conjugated antibodies, could be stored at 4°C in the dark for at least a week prior to FACS analysis. This method should prove useful to those who work with in vivo derived specimens or have limited access to flow cytometry facilities.