What is Freund's Adjuvant?
Freund’s Adjuvant is perhaps one of the most commonly used adjuvants in research today. It is used in animal research to trigger a humoral antibody inflammatory response for the production of high titer antibodies.
CFA versus IFA
There are two types of Freund’s adjuvant: complete and incomplete. Complete Freund’s Adjuvant, or CFA, is a water in oil emulsion, which also contains inactivated mycobacteria (Mycobacterium tuberculosis is most frequently used). Incomplete Freund’s Adjuvant, or IFA, is the same water in oil emulsion, but does not contain the mycobacteria pathogen.
Being one of the most effective adjuvants currently available, it is essential for antibody production protocols and research. The adjuvant stimulates antibody production through two different mechanisms: the depot effect, and nonspecific immune-potentiation of macrophages.
CFA may be a good adjuvant for certain types of antigens, including antigens that are:
- Difficult to obtain
- Of small molecular weight
- Weakly immunogenic
- Only available in very small quantities
However, there are several serious concerns about the use of CFA. The primary concern is that the adjuvant can cause severe pain at the injection site of the animal being used. It also has the potential to cause serious complications, such as abscesses, chronic granulomas, and ulcerating tissue necrosis. Subcutaneous injections of the emulsion can cause fistulous tracts. If injected intramuscularly, the emulsion can spread to distant muscles or organs in the animal. At a minimum, close observation of the injection site and other general health parameters is essential when using CFA.
Using Freund's Adjuvant
To mitigate some of the concerns of using CFA, its use is generally recommended as only being used for the initial injection. IFA can be used for subsequent injections because the side effects tend to be less severe.
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