Figure 1. Proposed model of adaptive immune system activation by inflammasome stimulation with the adjuvant aluminium hydroxide.

Alum and antigen are phagocytosed by an APC and, through an unknown mechanism, activate the Nlrp3 inflammasome, resulting in secretion of the pro-inflammatory cytokines IL-1β, IL-18 and IL-33 and potentially other immune modulatory molecules. In conjunction with antigen recognition on the APC by the T-cell receptor (TCR), IL-1 receptor (IL-1R) stimulation (or another inflammasome-dependent signal) provides ‘signal 2’ for CD4⁺ T-cell priming, the first step in generation of adaptive immunity.