Suppression of hepatic allograft rejection in the rat by mitomycin C-treated donor splenocytes: in situ splenic distribution of donor class I major histocompatibility complex antigen-positive cells in the recipient

Mitomycin C treatment improves pancreatic islet graft longevity in intraportal islet transplantation by suppressing proinflammatory response

The in vitro culture period prior to cell transplantation (i.e. pancreatic islet transplantation) enables cell modification and is thus advantageous. However, the islet preconditioning method has not been fully explored. Here we present a simple approach for islet preconditioning that uses the antibiotic mitomycin C (MMC), which has antitumor activity, to reduce islet immunogenicity and prevent proinflammatory events in an intraportal islet transplantation model. Freshly isolated mice islets were treated for 30 min with 10 μg/mL MMC or not, cultured for 20 h and transplanted into the livers of syngeneic or allogeneic diabetic mouse recipients. In the allogeneic model, MMC preconditioning significantly prolonged graft survival without requiring immunosuppressants. In vitro, MMC treatment suppressed the expression of proinflammatory cytokines in islet allografts, while immunohistochemical studies revealed the suppression of inflammatory cell infiltration into MMC-treated allografts relative to untreated allografts. Furthermore, MMC preconditioning significantly suppressed the mRNA expression of proinflammatory cytokines into the transplant site and induced the differentiation of regulatory T cells with the ability to suppress CD4⁺ T cell-mediated immune responses. In conclusion, islet preconditioning with MMC prolonged graft survival in an intraportal islet transplantation model by suppressing proinflammatory events and inducing potentially regulatory lymphocytes.

Splenectomy during whole liver transplantation: a morbid procedure which does not adversely impact long-term survival

BACKGROUND

Indications for splenectomy (SP) during whole liver transplantation (LT) remain controversial and SP is often avoided because of common complications. We aimed to evaluate specific complications of these combined procedures.

METHODS

Data were retrospectively analysed. Splenectomy was performed in patients with splenorenal shunt and/or splenic artery aneurysms or hypersplenism. Patients undergoing simultaneous transplantation and splenectomy (LTSP group) were matched to a non-splenectomy group (LT group).

RESULTS

Between 1994 and 2013, we included 47 and 94 patients in LTSP and LT groups, respectively. The LTSP patients had a higher rate of pre-LT portal vein thrombosis (PVT). The LTSP group had a longer operative time and greater blood loss. Mean follow-up was 101 months and 5-year survivals were identical (LTSP 85% vs LT 88%, p = 0.831). Hospital morbidity and rejection incidence were comparable, whereas de novo PVT (34% vs 2%, p < 0.0001) and infection (47% vs 25%, p = 0.014) rates were higher after SP.

CONCLUSION

Splenectomy during LT is technically demanding and exposes recipients to a higher thrombosis rate, therefore portal vein patency must be specifically assessed postoperatively. In selected recipients, SP can be performed without increased mortality but at the price of worsening outcome as evidenced by greater risk of infection and PVT.

Specific immunosuppression by postoperative infusion of allogeneic spleen cells: requirement of donor major histocompatibility complex expression and graft-versus-host reactivity

BACKGROUND

Donor leukocytes may exert positive immunoregulatory effects on allograft acceptance. Most recent studies have focused on pretreatment protocols. In this study, the effect of postoperative infusion of donor leukocytes on graft survival and the phenotypic and functional requirements for infused cells were investigated in fully major histocompatibility complex (MHC)-mismatched rat heart transplant models.

METHODS

LEW (RT1l) heart grafts were implanted heterotopically into abdomens of LEW.1W (RT1u), and different types of cells were infused postoperatively. Immunohistochemistry was used to evaluate histopathological changes of grafts.

RESULTS

In the absence of any immunosuppressive agents, a single dose of viable donor spleen cells (SC), but not bone marrow cells, was able to prolong heart allograft survival to about 21 days, while they were rejected promptly at day 7 in controls. Infusion of T cell-depleted donor SC, irradiated donor SC or third-party (BN) SC showed no effect on graft survival. Compared with resting cells, neither in vitro nor in vivo prestimulation of infused donor SC improved graft survival. Clinical signs of graft-versus-host reaction were not observed in all above groups. Histology showed remarkable reduction in the severity of graft infiltrate and interleukin-2 receptor-positive cells in grafts of cell-treated animals. Postoperative infusion of SC of F1 generation between different strain combinations showed two requirements for infused cells to be effective: (1) expression of donor-type MHC antigens and (2) strong alloreactivity against the host MHC antigens.

CONCLUSION

Postoperative infusion of viable donor SC can lead to allospecific down-regulation of alloreactivity by a graft-versus-host-associated effect.

Phenotype and localization of macrophages expressing inducible nitric oxide synthase in rat hepatic allograft rejection

BACKGROUND

We investigated the phenotype and localization of macrophages expressing inducible nitric oxide synthase (iNOS) in rat hepatic allografts, using double immunostaining with anti-macrophage iNOS (macNOS) and rat anti-macrophage (ED1 or ED2) monoclonal antibodies.

METHODS

The animals were divided into three experimental groups: group 1, isografts; group 2, untreated hepatic allografts; and group 3, hepatic allografts treated with FK506.

RESULTS

Plasma nitrite/nitrate concentrations in group 2 increased on day 3, peaked on day 5, and decreased thereafter. In contrast, the plasma nitrite/nitrate concentrations in group 1 increased slightly on day 3, but decreased gradually thereafter. The plasma concentrations of nitrite/nitrate did not vary in group 3. The peak nitrite/nitrate values in group 2 were significantly greater than those in groups 1 and 3. The number of macNOS+ cells peaked on day 5 in group 2. In contrast, a few macNOS+ cells were seen in the liver grafts of groups 1 and 3. Double immunostaining revealed that the macNOS+ cells consisted of macNOS+ ED1+ (80%) and macNOS+ ED2+ (40%) in the untreated hepatic allografts on day 5. In addition, a number of macNOS+ cells also were seen in the red pulp of the recipient spleen in the untreated hepatic allografts.

CONCLUSIONS

These results suggest that the intense iNOS expression by the monocyte/macrophage lineage among the hepatic infiltrates and by the splenic macrophages after transplantation supports a role for nitric oxide in the immunomodulation of allogeneic responses in local and remote organs, and possibly serves as a mediator of cytotoxic graft damage.