Hi Pandiarajan,

We have done measurements of monocyte-platelet aggregates in fixed whole blood samples, they can be analysed up to 3 days after fixation. You can use lysing solution to get rid of the red cells, or you can also just use fluorescent triggering (set a threshold on the fluorochrome of the leucocyte-specific antibody) - this way you avoid additional washing steps. If you need more details please let me know, we would be happy to help.

Thank you Dr Dovlatova for your helpful comments. I wish to know how much time you would wait after adding lysing solution. I am worried that time prolongation in this step would lyse the platelets too. 

You can use multiple ways to lyse erythrocytes. The simplest way is to vortex tube and add distilled water drop by drop for 30 S to 1 min depending on erythrocytes population. After that add same amount 2XPBS solution and spin on 1400 rpm for 5 min. You will get erythrocytes encriched population. 

We used FACS lysing solution and it worked  very well. We tried a number of other lysis buffers including those we made ourselves and the results were not great. So we had to use this one though it is not cheap but it works the best. 

Thank you all for the helpful comments. Of course, I have to fix the samples early to prevent in vitro activation of platelets. Also I have to lyse  the RBCs. The dilemma now is whether would I be able to lyse the RBCs after fixing the samples with paraformaldehyde.

Is there any way that I could lyse and fix at the same time so that I would not give time for platelet activation in vitro. 

FACS lysing solution contains formaldehyde. It lyses AND fixes in one step.

Thank you very much for this information.