Vaccines require the use of an adjuvant, or booster, to achieve maximum effects. The most common type of adjuvant in human vaccination is alum (pictured left), but despite its wide use for the past 90 years, its mechanism of action was not understood. Yan Shi and his colleagues from the University of Calgary have now remedied that situation. It turns out that alum binds to and activates dendritic (D) cells.
During an immune response, it’s the job of D cells to engulf antigens and transfer them to the D cell surface. The antigens are thus presented to the other immune cells, including those involved in antibody manufacture. Without an adjuvant, the antigens in vaccines are only poorly uptaken by the D cells. By using a new technique called single cell force spectroscopy, the team was able to show that alum binds very strongly to the D cell membrane. This binding alters the D cell plasma membrane so that it now readily absorbs antigens.
This new data may lead to even more effective vaccines.