Figure 2.

Antigen transfer in the intestine. (A) Intercellular transfer of harmless Ag establishes intestinal homeostasis. Gut-resident CX3CR1⁺ macrophages (Mφ) continuously sample the gut lumen for harmless soluble Ag, including Ag from dietary proteins and commensal bacteria. Subsequently, Mφ captured Ag is transferred to intestinal migratory CD103⁺ DCs, which then migrate back to the dLNs to induce T cell tolerance, establishing intestinal flora homeostasis and preventing food allergy. (B) Intercellular transfer of pathogenic Ag induces pro-inflammatory responses against infection. Upon intestinal invasion of pathogenic bacteria and viruses, CX3CR1⁺ Mφ collect potentially pathogenic Ag from infected intestinal tissue cells or directly from the pathogen, which was further transferred to CD103⁺ DCs through gap junctions and EVs for presentation and T cell activation, inducing specific protective immune responses.