Could you please tell us what you need to do? It is impossible to help at this point.

For example, yes, we use frozen samples every day, as we need to test whether or not the stem cells survived being frozen in the first place...

Without knowing anything about the kind of experiment you want to do, we cannot help.

Since you want to perform flow analysis I assume you are interested in leukocytes from the blood. The best course would be to isolate the leukocytes from your blood sample and then you can freeze them for flow analysis later. We have done that and it does work fine as long as your measurements are intended for those molecules that are not affected by temperature shock.  

If you isolate PBMC an Freeze/thaw them using proper/gentle conditions, it should work fine in most instances. However, some cell types are very sensitive to freeze/thawing.

Some cells can be activated due to freeze/thaw cycle. So be careful if you are interested in this sort of markers. Just remember to analyse a sample of fresh cells to compare with unfrozen ones.

If monocytes are of interest, this paper by Berg et al 2012 has a method from frozen leukocytes.

http://www.ncbi.nlm.nih.gov/pubmed/22238190

Thanks everybody for your suggestions. WE are interested in doing lymphocyte phenotying, NK activity and intracellular cytokine staining. What we are interested in is that we will be getting whole blood samples from patients around the world and it is difficult some to get the blood within 24 h as that is what is required so we were thinking if we can still preserve integrity by freezing them and then isolating leukocytes .As samples will be coming from doctors clinic we cannot ask them to isolate cells and then freeze them...... we will be doing  some comparision study but looking for if anybody else has an experience.........