Intestinal reengineering: Scientific advances in intestinal transplantation

Figure 1 The historical development and challenges of intestinal transplantation. TPN: Total parenteral nutrition; ITx: Intestinal transplantation; CR: Chronic rejection; AMR: Antibody-mediated rejection; FMT: Fecal microbiota transplantation; JAK: Janus kinase.

Figure 2 Schematic representation of the multiple pathway activation mechanisms of the anti-graft response in the intestinal transplant host. Pathway 1: Direct pathway [donor antigen-presenting cell (APC) presenting donor MHC]; Pathway 2: Indirect pathway (recipient APC presenting donor MHC acquired by endocitic pathway); Pathway 3: Semi-direct pathway (recipient APC presenting donor MHC acquired by membrane vesicles); Pathway 4: Inverted direct pathway (donor T cells is activated by recipient MHC presented by recipient B cells). Organized lymphoid tissue in the graft significantly enhances the alloimmune response. It should be noted that pathways 1-3 can occur both in the absorptive mucosa and in the organized lymphoid tissue. All four pathways are activated in the early post-transplantation period, whereas only pathways 2 and 3 persist in long-surviving grafts. APC: Antigen-presenting cell.