Immunologist's Dirty Little Secret

Table from here at New Scientist.

The "dirty little secret" of immunologists was spilled by immunologist Charlie Janeway back in 1989. He let it be known to the world that most vaccines would not be effective unless a little secret ingredient was added. The secret ingredient is alum (aluminum hydroxide or sodium aluminum sulfate). And this is the only adjuvant approved for human use.

Now it appears we are one step closer to understanding how alum does its job. Alum appears to cause cells at the injection site to produce uric acid. The uric acid, in turn, stimulates the production of several factors that activates antigen-presenting dendritic cells.

The key to a powerful adjuvant is that it must be capable of immitating a
pathogen-associated molecular pattern. Our immune systems have evolved to recogize these PAMPs by having pattern recognition receptors (PRR) on some types of phagocytic cells. Other PRR's, called Toll-like receptors, are found on the surface of macrophages and dendritic cells - cells that are important in kick-starting the immune response.

Effective vaccines against many pathogens will not be developed until a more potent adjuvant that can be safely used in humans is found.