Cohn process

A method for fractionating blood plasma

The Cohn process is a method used for the fractionation of blood plasma into its component proteins. This process was developed by Edwin J. Cohn and his colleagues in the 1940s and has been instrumental in the production of various plasma-derived products used in medicine.

Overview

The Cohn process involves the use of cold ethanol fractionation to separate plasma proteins based on their solubility at different concentrations of ethanol, pH levels, and temperatures. This method allows for the isolation of specific proteins such as albumin, immunoglobulins, and fibrinogen, which are essential for various therapeutic applications.

Process Steps

The Cohn process is typically divided into several steps, each designed to precipitate different proteins:

Fraction I

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Fraction I precipitation

In the first step, the plasma is cooled and mixed with ethanol to a concentration of about 8%. This results in the precipitation of fibrinogen, which is then removed by centrifugation.

Fraction II and III

The ethanol concentration is increased to about 25%, and the temperature is adjusted to precipitate the immunoglobulins, primarily IgG. This fraction is crucial for the production of intravenous immunoglobulin (IVIG) products.

Fraction IV

Further adjustment of ethanol concentration and pH leads to the precipitation of various other proteins, including some alpha globulins and beta globulins.

Fraction V

The final step involves increasing the ethanol concentration to about 40%, which precipitates albumin. Albumin is a major plasma protein used in the treatment of shock and burns.

Applications

The Cohn process is used to produce several important plasma-derived products:

• Albumin: Used in the treatment of shock, burns, and hypoalbuminemia.
• Immunoglobulins: Used for immune deficiencies and autoimmune diseases.
• Coagulation factors: Used in the treatment of bleeding disorders such as hemophilia.

Advantages and Limitations

The Cohn process is advantageous because it allows for the efficient separation of plasma proteins with high purity. However, it requires careful control of temperature, pH, and ethanol concentration, and the process can be labor-intensive and time-consuming.

Related pages

• Blood plasma
• Edwin J. Cohn
• Plasma protein
• Fractionation