Polymorphprep Application Sheet
The theory of the separation is that the polysaccharide aggregates the erythrocytes and causes them to sediment rapidly through the medium, ahead of the leukocytes. In Figure 1, the column of Polymorphprep is divided hypothetically into three zones.
When the erythrocytes enter the top zone (A), there is a large difference in osmolality across the erythrocyte membrane, which causes water to move from the erythrocytes into the medium (thereby diluting it significantly), while the osmolality inside the erythrocytes increases.
Consequently, when these erythrocytes sediment into the middle zone (B), the difference in osmolality across the erythrocyte membrane is now less pronounced, so the erythrocytes lose less water than they did in the top zone, the medium is consequently diluted less.
In the bottom zone the difference in osmolality across the erythrocyte membrane and consequently the loss of water into the medium, are reduced further (C). In this way, the density of the medium is decreased most in the top zone and least in the bottom zone and a gradient is generated (D).
In reality, the erythrocyte
sedimentation and medium dilution changes occur progressively and smoothly; the gradient is therefore
continuous rather than discontinuous. It is within this continuous gradient that the mononuclear and
PMNs are resolved (see Figure 2). The standard protocol is described on p2.