For examination of lymphocytes and abnormal cells
it was found desirable to remove phagocytic cells
and this was done by mixing the blood sample
with approximately one third its volume of 1%
methyl cellulose (Dow) and incubating this with
carbonyl iron powder (G.A.F. Chemical Division,
Manchester) 100 mg/20 ml blood (Coulson and
Chalmers, 1967). The tube was shaken gently by
repeated inversion on a slow rotator for 30 minutes
at 37°C. The mixture was then placed over a magnet
for 15 minutes and the clumps of iron particles and
most of the phagocytic cells allowed to sediment.
The lymphocyte-enriched supernatant was layered
onto a preliminary gradient of Ficoll-Triosil and
spun at 400 g for 20 minutes (Harris and Ukaejiofo,
1970).