Expression of four canine leukocyte adhesion factors in fresh and stored whole blood samples evaluated using a no-lyse, no-wash method

Expression of four leukocyte adhesion factors on canine leukocytes was studied by flow cytometry using a no-lyse, no-wash method. The effect of fixation and storage for up to 14 days in 1% paraformaldehyde on labelled samples and within assay variation was evaluated. Monoclonal antibodies directed to monocyte marker CD14, and to adhesion molecules CD11a, CD18, CD32 and CD49d were used. Cell surface marker, cell population, time, and the interactions between time and cell marker significantly affected expression of cell adhesion factors. For CD18, there was a significant difference in mean fluorescence intensity (MFI) between fresh and stored samples (P < 0.001), but no significant difference between stored samples. The MFIs of CD11a and CD49d were not significantly affected by fixation and storage. The CVs differed significantly depending on cell marker (P < 0.001) and cell population (P = 0.005). Fixation and storage did not significantly affect the CV. In conclusion, a no-lyse, no-wash method can be applied to canine leukocytes. The effect of fixation and storage on the resulting MFI differs between monoclonal antibodies, and should be evaluated for each antibody before use. The coefficient of variation was generally acceptable, and high CVs were related to a low MFIs or low numbers of analysed cells.