Figure 2.

T cell priming in different mucosal sites following mucosal vaccination. Mucosal vaccination targets the epithelium that covers mucosal surfaces. (A) In many mucosal sites, such as the gastro-intestinal and respiratory tracts, underneath the epithelium barrier inductive sites are present, constituted by organized lymphoid tissue. Following vaccination, antigen is sampled by local DCs and transported into the inductive site where antigen-specific T cell priming occurs. Activated T cells migrate from the inductive site toward the regional draining LNs and then enter into the circulatory torrent through the lymphatic system. (B) Vaginal mucosa is devoid of histologically demonstrable organized mucosa-associated lymphoid tissue, therefore after immunization, the antigen is sampled by tissue-resident DCs and transported into the draining iliac LNs that constitute the inductive site. Primed T cells exit the LNs and migrate through the lymphatic system into the blood. (C) A fraction of mucosally primed T cells transiently circulates through the blood into the spleen and disseminates into non-draining LNs; the entry into peripheral LNs is CD62L-dependent, while into mesenteric LNs depends on both CD62L and α4β7 expression.