Freund’s Adjuvant was first developed in the 1940s by Jules Freund. It is largely used in immune research, particularly in animal immune research. It is an aqueous solution of antigens, which is used by mixing an equal proportion of water and oil, usually paraffin oil or vegetable oil. It becomes an antigen emulsion when an emulsifier, such as lanolin or leaf tween 80, is added to the mixture. While Complete Freund’s Adjuvant contains slaughtered Mycobacterium tuberculosis, the incomplete version of Freund’s adjuvant does not include the bacteria.
Incomplete Freund’s adjuvant is usually prepared with a mixture of 2 parts of liquid paraffin and one part of lanolin, but the ratio may be 1-5:1, according to the need. An incomplete adjuvant can be transformed into a complete Freund’s adjuvant with the final concentration of 2-20 mg/ml of BCG or killed Mycobacterium tuberculosis. Usually, during the first injection, emulsification is used with 1/2 volume of FCA and antigen, and no adjuvant is used for the subsequent second and third inoculation. The antigen volume can be increased by 10 to 20 times without adding an adjuvant.
The purpose of using Freund’s Adjuvant is to get antigens continuously, which are essential for inspiring a strong, persistent immune response. It is because the mycobacteria in Complete Freund’s adjuvant are capable of attracting macrophages and other cells to the inoculation spot, thus improving the immune response. It makes Complete Freund’s Adjuvant appropriate to use for the first immune response, as it works as a booster and reduces side effects.
Although there are several types of adjuvants available on the market, Freund’s Adjuvant stands separate from them. This is for the reason that it offers unique benefits to users. Freund’s Adjuvant is considered one of the most effectual adjuvants, making it indispensable for antibody manufacture protocols and study. Additionally, the adjuvant is capable of stimulating antibody production through two effective different mechanisms, such as the unfocused immune potentiation of macrophages and the depot effect. Both types of Freund’s Adjuvant have been used for over 70 years in the research fields. These adjuvants are mostly used for enhancing the immune response of the animal such as mouse and rabbit to an antigen.