Adjuvants
See also main article on adjuvants in immunology.
The use of simple molecules such as toxoids for immunization tends to produce a low response by the immune system, and thus poor immune memory. However, adding certain substances to the mixture, for example adsorbing tetanus toxoid onto alum, greatly enhances the immune response. These substances are known as adjuvants. Several different adjuvants have been used in vaccine preparation. Adjuvants are also used in other ways in researching the immune system.
A more contemporary approach for "boosting" the immune response to simpler immunogenic molecules (known as antigens) is to conjugate the antigens. Conjugation is the attachment to the antigen of another substance which also generates an immune response, thus amplifying the overall response and causing a more robust immune memory to the antigen. For example, a toxoid might be attached to a polysaccharide from the capsule of the bacteria responsible for most lobar pneumonia.
Read more about this topic: Artificial Induction Of Immunity