Immunotolerance of liver allotransplantation induced by intrathymic inoculation of donor soluble liver specific antigen

Immunological Tolerance in Liver Transplant Recipients: Putative Involvement of Neuroendocrine-Immune Interactions

The transplantation world changed significantly following the introduction of immunosuppressants, with millions of people saved. Several physicians have noted that liver recipients that do not take their medication for different reasons became tolerant regarding kidney, heart, and lung transplantations at higher frequencies. Most studies have attempted to explain this phenomenon through unique immunological mechanisms and the fact that the hepatic environment is continuously exposed to high levels of pathogen-associated molecular patterns (PAMPs) or non-pathogenic microorganism-associated molecular patterns (MAMPs) from commensal flora. These components are highly inflammatory in the periphery but tolerated in the liver as part of the normal components that arrive via the hepatic portal vein. These immunological mechanisms are discussed herein based on current evidence, although we hypothesize the participation of neuroendocrine-immune pathways, which have played a relevant role in autoimmune diseases. Cells found in the liver present receptors for several cytokines, hormones, peptides, and neurotransmitters that would allow for system crosstalk. Furthermore, the liver is innervated by the autonomic system and may, thus, be influenced by the parasympathetic and sympathetic systems. This review therefore seeks to discuss classical immunological hepatic tolerance mechanisms and hypothesizes the possible participation of the neuroendocrine-immune system based on the current literature.

[Thymus function and autoimmunity]

PURPOSE

Thymus is the site of T-cell development and is essential for the induction of self-tolerance, by deletion of autoreactive T lymphocytes (negative selection) and by generation of regulatory T cells. Defect of the selection mechanism of both types of lymphocytes lead to autoimmune diseases.

CURRENT KNOWLEDGE AND KEY POINTS

Elimination of potentially self-reactive T cells in the thymus requires the intrathymic expression of ubiquitous and "tissue-specific" antigens. Some thymic antigen expressions are dependent on AIRE expression. Mutations in the AIRE gene that are associated with the absence of autoantigen expression in the thymus, defects in the peptide presentation or in apoptosis can allow autoreactive T cells to escape negative selection, and are associated with autoimmune diseases. Recent data are now available concerning the thymic selection of autoreactive regulatory T cells. The Foxp3 gene was recently shown to be predominantly expressed in regulatory T cells and could be a more specific marker of regulatory T cells than phenotypic markers.

FUTURE PROSPECTS AND PROJECTS

Animal models show that regulatory T cells injection or intrathymic inoculation of antigen lead to immunological tolerance in autoimmunity and transplantation. These novel strategies could be used in human.

Involvement of NF-kappa B activation in P-glycoprotein expression in vincristine-resistant human gastric cancer cells

AIM: To investigate the effect of vincristine on activation of nuclear factor-kappa B (NF-κB) and expression of p-glycoprotein (P-gp) in vincristine-resistant human gastric cancer SGC7901 cells (SGC7901/VCR) and the parent sensitive clone (SGC7901).

METHODS: NF-κB-DNA binding activity was determined by electrophoretic mobility shift assay (EMSA). Levels of inhibitory B (IB-) and P-gp were measured by cellular-ELISA. And immunocytochemistry was used to detect the translocation of P65.

RESULTS: IN comparison with the parent SGC7901 cells, the basal and vincristine-induced NF-κB-DNA binding activity at various concentrations were all higher in the SGC7901/VCR cells. Concurrent with the NF-κB activation, vincristine-induced IB- degradation and P-gp upregulation were also found to be highly enhanced in the SGC7901/VCR cells than that in the sensitive SGC7901 cells. In the SGC7901/VCR cells, the activation of NF-κB induced by vincristine showed a positive relation with the level of P-gp expression (r = 0.977, P < 0.01). And nuclear translocation of P65 occurred concomitantly with NF-κB activation. Furthermore, the inhibition of NF-κB by MG-132, a proteasome inhibitor, could reduce NF-κB activation, IB- degradation and P-gp upregulation.

CONCLUSION: The enhancement of NF-κB activation correlates with vincristine resistance and NF-κB may play an important role in the regulation of the P-gp expression.

Influence of liver nonparenchymal cell infusion combined with cyclosporin A on rejection of rat small bowel transplantation

AIM: To investigate the effect of liver nonparenchymal cell infusion combined with cyclosporin A (CsA) on rejection of heterostrain rat small bowel transplantation.

METHODS: The liver nonparenchymal cell suspension was prepared by density gradient centrifugation method with Percoll centrifugal solution. Heterotopic small bowel transplantation was performed. Then the rats were divided into four groups. Group one: homogenic transplantation (F344/N→F344/N), group two: allotransplantation (F344/N →Wistar), group three: allotransplantation (F344/N→Wistar) + CsA, with CsA 10 mg·kg^-1·d^-1 after transplantation, group four: allotransplantation + CsA (F344/N→Wistar) + liver nonparenchymal cell infusion + CsA (F344/N→Wistar), in which recipient Wistar rats had been injected with 2 × 10⁸ F344/N liver nonparenchymal cells 20 days before transplantation, and treated with CsA after transplantation. Finally, the survival time after small bowel transplantation, gross and histopathological examination, and IL-2 levels in serum were observed.

RESULTS: The survival time after small bowel transplantation was 7.14 ± 0.33 d, 16.32 ± 0.41 d and 31.41 ± 0.74 d in group 2, 3, and 4, respectively. The survival time was significant longer (P < 0.01) in group 4. The gross and histopathological examination showed that the rejection degree in group 4 was lower than those in groups 2 and 3. Serum IL-2 level in group 4 was also lower than those in groups 2 and 3 (P < 0.01).

CONCLUSION: Liver nonparenchymal cell infusion combined with CsA can prolong the survival time of rat small bowel transplantation, and the anti-rejection effect is good.