https://orcid.org/0000-0001-8365-5552
Figures & data
Figure 1. The mucosal adaptive immune system. Based on anatomical and functional properties, the mucosal adaptive immune system can be divided into inductive and effector sites. B cells and T cells undergo activation and clonal expansion in the inductive site. The differentiated effector cells then migrate through the peripheral lymphatic system to the effector sites present in all parts of the mucosa, where they perform specific functions upon activation, such as antibody production and cell-mediated immune responses. SIgA: secretory immunoglobulin A; pIgR: polymeric immunoglobulin receptor.
Table 1. Licensed mucosal vaccines to date.
Table 2. Recently developed technologies and materials for mucosal delivery of primarily subunit, DNA and mRNA vaccines.
Figure 2. Compartmentalization of the common mucosal immune system. Although different inductive sites can share the location of effector sites where IgA-secreting cells are seeded, the phenomenon of compartmentalization in the common mucosal immune system is evident. Different mucosal vaccination routes can produce an immune response in specific MALT areas, therefore exploitation of compartmentalization within the common mucosal immune system can direct the immune response to a particular site used by the pathogen for invasion, to effectively counter the development of infection.
Figure 3. Tolerance versus immunity at mucosal sites. The nature of the antigen as well as the type of antigen-presenting cell determines the type of immune response induced at the mucosa. In general, protein antigens induce regulatory and/or inhibitory response which by default leads to tolerance. Tregs negatively regulate Th1 and Th2 cells by producing cytokines such as IL-10 and TGF-β, thereby maintaining homeostasis. On the other hand, adjuvanted antigen or natural infection can induce strong cellular and humoral immune responses and prevent mucosal tolerance. Adjuvants support the induction of effectors by triggering innate immunity, which recruits unconditioned DCs from other sites to initiate an antigen-specific immune response or acquired immunity.
