1. Put 3 ml of Ficoll-Paque* into a sterile centrifuge tube.
2. Carefully overlay 4 ml of a 50:50 mix of defibrinated blood and balanced salts solution
3. Centrifuge at 400xG for 30-40 minutes at room temperature.
   (Don't spin faster or the cells will be killed - be patient and take the 30-40 minutes!)
4. Draw off the clear serum and save.
5. Transfer lymphocyte layer and bottom of tube to a clean centrifuge tube
   Take a minimal amount of serum or FP-layers
6. Add 3 volumes of balanced salts solution
7. Suspend cells gently
8. Centrifuge at 60-100xG for 10 minutes at room temperature
9. Decant and suspend lymphocyte pellet in balanced salts solution.
10. Lymphocyte concentration can be assayed via hematocrit.

* Ficoll-Paque is from Pharmacia