Adjuvants and antibody production: dispelling the myths associated with Freund's complete and other adjuvants

Adjuvants have been used for more than 70 yr to enhance the immune response of the host animal to an antigen. Among the mechanisms that adjuvants use to enhance the immune response are the "depot" effect, antigen presentation, antigen targeting, immune activation/modulation, and cytotoxic lymphocyte induction. The immunostimulatory properties of adjuvants result in inflammation, tissue destruction, and the potential for resulting pain and distress in the host animal. The inflammatory lesions produced by adjuvants such as Freund's complete adjuvant (FCA) have led some to conclude that pain and distress are present, even in cases where the scientific evidence fails to support this conclusion. Recommendations and regulations in the literature, based on available scientific evidence, provide guidance on total adjuvant volumes, volumes per site, routes of injection, booster injections, and adjuvants used for antibody production. Among the numerous adjuvants that are used for experimental antibody production reviewed in this article, many claim to be less inflammatory, tissue destructive, and painful than FCA while producing equal or superior antibody responses. Although no adjuvant surpasses FCA for experimental antibody production against a wide range of antigenic molecules, many produce excellent antibody responses with less inflammation and tissue destruction. Balancing the requisite degree of immuno-stimulation and the extent of inflammation, necrosis, and potential pain and distress requires consideration of the nature of the antigen, the host immune responsiveness, the adjuvant's mechanisms of action, and the desired end-product. In cases where the antigen is a weak immunogen or has a very limited availability, the type and role of adjuvant becomes a critical component in producing an acceptable immune response and humoral antibody response.