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one end separated from the media container by a membrane. Others have capillary

systems formed from membrane running through the cell culture compartment and in

these the media is pumped through the cartridge to facilitate nutrient and gas

exchange. These systems do produce high yields of antibody but can be problematical

to set up and run. They are ideal where large quantities of monoclonal antibody are

needed and space is at a premium. They are however prone to contamination by yeasts

and great care must be exercised when handling them. Cells are grown in bioreactors

for up to 6 weeks so the clone used must be stable and it is advisable to carry out

studies on long-term culture prior to embarking on this form of culture. The major

advantage of bioreactor culture is that the antibody is produced in high concentration

without the presence of media components making it easy to purify. Total quantities

per bioreactor run may be several hundred milligrams to gram quantities.

7.2.9 Antibody purification

The choice of method used for the purification of antibodies depends very much on

the fluid that they are in. Antibody can be purified from serum by the addition of

chaotropic ionsin the form of saturated ammonium sulphate. This preferentially

precipitates the antibody fraction at around 60% saturation and provides a rapid

method for IgG purification. This method does not work well in tissue culture

supernatant as media components such as ferritin are co-precipitated. Ammonium

sulphate precipitation may be used as a preparatory method prior to further

chromatographic purification.

Media vessel Cell growthvessel

Harvesting

port

Air filter

Rotating bioreactor

utilising two

compartments to

separate growth

medium from cells

and antibodies

Hollow fibre

bioreactor utilising

a capillary network

to separate growth

medium from cells

and antibodies

Media flow
through
capillary spaces

Semi permeable membrane

Cell growth around

capillaries

Harvesting port

Fig. 7.8Bioreactors for antibody production.

281 7.2 Making antibodies