Depot effect (adjuvant mechanism)

The depot effect is a classical immunological concept describing how certain adjuvants (such as mineral salts—e.g., alum—or oil emulsions like incomplete Freund's adjuvant) enhance the immune response by retaining antigen at the injection site, prolonging antigen exposure and release. This sustained presence recruits and activates innate immune cells, facilitates antigen uptake by APCs, and promotes efficient antigen transport to draining lymph nodes for adaptive immune activation. The depot effect is considered one of several mechanisms by which adjuvants enhance vaccine immunogenicity, alongside direct immune stimulation via pattern-recognition receptors, cytokine induction, and immune polarization. It is not a molecular target but a phenomenon arising from how adjuvant formulations interact with the immune system.

Other names

depot effectadjuvancyimmune potentiation by adjuvantvaccine adjuvant effect

Prolonged antigen retention at the site of injection, local immune cell recruitment and activation, enhancement of antigen uptake by antigen-presenting cells (APCs), induction of cytokine/chemokine production