During a practical exercise on PBMCs cytometry, the PBMCs was not separated in one group's blood sample after centrifugation. What could account for this? Is it possible the PBMCs of some individuals blood cannot be separated? If yes why?
As such there is no disease condition that could affect separation of PBMCs using ficol. There seems to be mechanical problem. Perhaps you should repeat the experiment using a different centrifuge or perhaps repeat the experiment using even the same centrifuge. Good luck.
If on a repeat experiment you found the same results then I will suggest that you get a complete blood Count (CBC) and see if the person has severe leukocytopenia. So if there is leukocytopenia there may be improper or no separation.