Isolation of polymorphonuclear leukocytes (granulocytes) from rat, mouse, guinea pig and rabbit blood
A common approach to the problem of isolating rodent and rabbit polymorphonuclear leukocytes (PMNs) was to use a density barrier of Nycoprep 1.077A ( = 1.077 g/ml, osmolality = 265 mOsm). The method was first published by Bøyum et al .
This customized medium separated the mononuclear cells (MCs), which band at the interface, from the PMNs and the erythrocytes, which sediment through the barrier to form a pellet. To retrieve the PMNs, the erythrocytes may be selectively lysed in isotonic ammonium chloride solution or ice-cold distilled water.
An alternative approach is to remove the erythrocytes from whole blood first by aggregation with dextran [2-4], methylcellulose [5,6] hetastarch  or Plasmagel [8,9] and then layer the resulting leukocyte-rich plasma (LRP) over the Nycoprep 1.077A, so that the PMN pellet contains only a very small percentage of residual erythrocytes.
Nycoprep 1.077A is no longer commercially available but an
iodixanol solution of the same density and osmolality can be easily prepared from OptiPrep and it is
this method that is described in Section 2.