THE EFFECT OF STORAGE ON IMMUNOPHENOTYPING OF SHEEP PERIPHERAL-BLOOD LYMPHOCYTES BY FLOW-CYTOMETRY

We have shown that when a whole blood method of cell staining is used for flow cytometric analysis of sheep lymphocytes (i.e. red cell lysis after addition of antibody), staining may be delayed for up to 48 h a fter blood collection without significant effect on expression of CD4, CD5, CD8 or B cell markers. If cells were stained immediately after b lood collection, using the same whole blood method, and then fixed wit h paraformaldehyde, cell samples could be stored for 24 h without chan ge in marker expression. However, by 7 days there was a significant de crease in the percentage of cells expressing CD8, T19 and B cell marke rs, Cryopreservation prior to staining was found to markedly affect th e expression of all cell surface markers investigated, These results i ndicate that storage of sheep blood prior to flow cytometric analysis is feasible but may affect the results obtained. Thus is it important to standardise the handling of samples, especially when comparative st udies are being undertaken.