Mechanism of portal venous tolerant long-term MHC Class I L(d)-specific skin graft survival in transgenic 2CF1 mice

[Proteasomes on thyroid tissue allotransplantation under induction of donor specific tolerance in rats]

The proteasomes in the liver of August rats (RT1C) were investigated 30 days after the allotransplantation of Wistar rat (RT1u) thyroid tissue under renal capsule with/without induction of donor specific tolerance by donor splenocyte intraportal administration. The level of the total proteasome pool, immune proteasomes containing the LMP2 and/or LMP7 subunits, proteasome 19S- and 11S-regulators was defined. The intact and sham-operated August rats were used as control groups. The level of all immune proteasome forms and 11S regulator increased while the level of the total proteasome pool and 19S regulator decreased in the liver of experimental animals compared to the control groups that indicated changes of liver functional state after transplantation. The 19S/11S ratio increased in the liver of non-tolerated rats compared to tolerated animals. In the liver of tolerated rats with survived transplants, the quantity of mononuclear cells, expressing the immune subunit LMP2, greatly increased in comparison with control and non-tolerated animals. Study of the survived transplants showed the increase of the ratio of LMP2/LMP7 immune subunits and 19S/11S regulators in them compared to the tissue replacing the rejected transplants. In the control intact thyroid tissue, the immune proteasomes were almost not revealed, while 19S/11S ratio was maximal. Thus, the development of the immune reaction or its suppression is accompanied by change of the balance between different proteasome forms. The immune subunit LMP7 and 11S regulator are connected with the response against donor tissue. On the contrary, the immune subunit LMP2 and 19S regulator are likely to be important for the immune tolerance development and survived tissue functioning. The low content of the immune proteasomes in the follicle cells was found by immunofluorescence assay. The formation of antigens for major histocompatibility complex class I molecules was impaired by low immune proteasome content that led to immunological tolerance to hormone-producing follicle cells.

Increased CD4+CD25+Foxp3+ regulatory T cells in tolerance induced by portal venous injection

BACKGROUND

A portal vein injection (PVI) of allogeneic donor antigen is known to prolong the survival of a subsequently transplanted allograft; however, the underlying mechanism remains to be clarified.

METHODS

Irradiated C57BL/6 (B6) splenocytes were injected into BALB/c mice via the portal vein. Seven days after injection, the proportions of CD4(+)CD25(+)Foxp3(+) regulatory T (Treg) cells were determined in the blood, liver, and spleen. CD4(+) and CD8(+) T cells were isolated from BALB/c mice that received PVI of B6 splenocytes (PVI mice), adoptively transferred into recipient BALB/c mice 1 day before B6 or third-party C3H heart transplantation, and graft survival was compared. B6 or C3H heart allografts were implanted into anti-CD25 monoclonal antibody (mAb)-treated PVI and untreated PVI mice, and graft survivals were compared. The percentages of CD4(+)CD25(+)Foxp3(+) Treg, cytokine profiles, and ratios of apoptosis were determined in anti-CD25 mAb-treated PVI and untreated PVI mice.

RESULTS

PVI of allogeneic cells induced antigen-specific tolerance and increased the percentage of CD4(+)CD25(+)Foxp3(+) Treg. Adoptive transfer of CD4(+) T cells, but not CD8(+) T cells, from PVI mice prolonged B6 heart allograft survival. Depletion of CD4(+)CD25(+) T cells prevented the induction of tolerance and decreased the percentage of CD4(+)CD25(+)Foxp3(+) Treg in the CD3(+) T-cell pool, and thus was associated with decreased production of interleukin (IL)-4 and apoptosis of T cells.

CONCLUSION

Increased CD4(+)CD25(+)Foxp3(+) Treg play an important role in portal vein tolerance induction, at least partly via increasing the production of IL-4 and decreasing apoptosis of T cells.

Short-term cyclosporine therapy and cotransplantation of donor splenocytes: effects on graft rejection and survival rates in pigs subjected to renal transplantation

BACKGROUND

Donor-specific allogeneic loading can prolong the survival of solid organ transplants by inducing a state known as acceptance. Several populations of cells are known to be involved in this process, but their exact roles have yet to be defined. The aim of this study was to assess the effects of portal-vein transfusion of donor-specific splenocytes (DST) after short-term cyclosporine A (CyA) therapy in pigs subjected to renal transplantation.

METHODS

Four groups of unrelated swine underwent renal transplantation with removal of the native kidneys. Antirejection protocols consisted in portal-vein DST (3 x 10(8) cells/kg) (Group 2, n = 7); intravenous CyA (9 mg/kg/d) on postoperative days 1-12 (Group 3, n = 14); and DST + CyA (as described above) (Group 4, n = 13). Results (through postoperative day 90) were compared with those obtained in untreated control recipients (Group 1, n = 7).

RESULTS

Compared with animals of Groups 1, 2, and 3, Group 4 recipients presented significantly longer survival (mean: 90 days, P < 0.01 in Kaplan-Meier analysis) and better renal function (P < 0.05). Graft histology revealed preserved parenchyma.

CONCLUSION

The role of spleen cells in the immune response has probably been underestimated. Cotransplantation of donor splenocytes seems to induce a certain degree of acceptance toward the renal allograft. The route of administration (portal-vein infusion in this study) may be crucial for developing favorable mechanisms of recognition.

Liver sinusoidal endothelial cells that endocytose allogeneic cells suppress T cells with indirect allospecificity

A portal venous injection of allogeneic donor cells is known to prolong the survival of subsequently transplanted allografts. In this study, we investigated the role of liver sinusoidal endothelial cells (LSECs) in immunosuppressive effects induced by a portal injection of allogeneic cells on T cells with indirect allospecificity. To eliminate the direct CD4+ T cell response, C57BL/6 (B6) MHC class II-deficient C2tatm1Ccum (C2D) mice were used as donors. After portal injection of irradiated B6 C2D splenocytes into BALB/c mice, the host LSECs that endocytosed the irradiated allogeneic splenocytes showed enhanced expression of MHC class II molecules, CD80, and Fas ligand (FasL). Due to transmigration across the LSECs from BALB/c mice treated with a portal injection of B6 C2D splenocytes, the naive BALB/c CD4+ T cells lost their responsiveness to stimulus of BALB/c splenic APCs that endocytose donor-type B6 C2D alloantigens, while maintaining a normal response to stimulus of BALB/c splenic APCs that endocytose third-party C3H alloantigens. Similar results were not observed for naive BALB/c CD4+ T cells that transmigrated across the LSECs from BALB/c FasL-deficient mice treated with a portal injection of B6 C2D splenocytes. Adaptive transfer of BALB/c LSECs that had endocytosed B6 C2D splenocytes into BALB/c mice via the portal vein prolonged the survival of subsequently transplanted B6 C2D hearts; however, a similar effect was not observed for BALB/c FasL-deficient LSECs. These findings indicate that LSECs that had endocytosed allogeneic splenocytes have immunosuppressive effects on T cells with indirect allospecificity, at least partially via the Fas/FasL pathway.

Alloantigen affinity and CD4 help determine severity of graft-versus-host disease mediated by CD8 donor T cells

TCR affinity dictates T cell selection in the thymus and also has a high impact on the fate of peripheral T cells. Graft-vs-host disease (GVHD) is a pathological process initiated by activation of donor T cells after adoptive transfer into an allogeneic recipient. How TCR affinity affects the potential of alloreactive T cells to induce GVHD is unclear. Using alloreactive CD4+ and CD8+ TCR transgenic (Tg) T cells, GVHD models are presented that allow for the visualization of how CD8+ alloreactive T cells behave in response to alloantigens with different TCR affinity in the absence or presence of CD4 help. In a nonmyeloablative transplant model where GVHD lethality is due to marrow aplasia, alloreactive CD8+ TCR Tg T cells induced significantly more severe GVHD in the recipients that express an intermediate-affinity alloantigen than in the recipients that express a high-affinity alloantigen. In a myeloablative transplant model where GVHD lethality is due to epithelium injury, CD8+ TCR Tg cells were also more pathogenic in the recipients with an intermediate-affinity alloantigen than in those with a high-affinity alloantigen. The presence of alloreactive CD4+ TCR Tg cells enhanced the potential of CD8+ TCR Tg cells to cause GVHD in recipients with an intermediate-, but not with a high-, affinity alloantigen. These findings underscore that alloantigen affinity and CD4 help control the fate and pathogenicity of alloreactive CD8+ T cells in vivo.

Regional oral tolerance in transgenic 2C mice

BACKGROUND

Antigen injected subcutaneously (SQ) results in a strong systemic immune response, whereas antigen infused orally or by the portal vein tends to induce tolerance. Nontransgenic C57BL/6J (H-2(b)), or B6, mice and transgenic 2C mice (that express a cytotoxic T cell receptor against major histocompatibility complex Class I L(d)) were used to investigate the regional and systemic responses to oral antigen.

METHODS

B6 (H-2(b)) and 2C (H-2(b)) mice were given either saline or BALB/cByJ (H-2(d), L(d+)) (BALB/c) spleen cells (SCs) (25 x 10(6)) by oral gavage (PO) on day 0. Injection of 10 x 10(6) BALB/c SCs SQ was performed after 7 days, followed by a footpad injection of 10 x 10(6) BALB/c SC on day 14. Specific footpad swelling was measured 24 hours later by means of a micrometer. Mixed lymphocyte culture was performed on splenic and mesenteric lymph node (MLN) lymphocytes. The percentage of splenic and MLN CD4+ and CD8+ T cells was quantitated by fluorescence activated cell sorter. Cytokine messenger RNA (mRNA) and protein was measured by reverse transcriptase-polymerase chain reaction and enzyme-linked immunosorbent assay.

RESULTS

Whereas B6 mice were shown to have specifically decreased responsiveness to Balb/c cells in vivo and in vitro after oral Balb/c, 2C mice did not demonstrate any downregulation in delayed-type hypersensitivity responsiveness or splenic lymphocyte proliferation. However, MLN lymphocytes from 2C mice did demonstrate decreased proliferation against Balb/c after oral Balb/c gavage (P < .01). Subset percentages of naïve B6 (n=8) spleen and MLN lymphocytes were 50% to 52% for CD4+ and 46% to 47% for CD8+ T cells. These percentages were unchanged in B6 mice after PO Balb/c. Subset percentages of naïve 2C (n=6) spleen and MLN lymphocytes were 2% to 5% for CD4+ and 61% to 64% for CD8+ T cells. After PO Balb/c, MLN CD4+ and CD8+ T cells were unchanged, whereas splenic CD8+ T cells decreased to 44% to 48% and CD4+ T cells increased to 32% to 33% (P < .05, P < .05 vs naïve 2C spleen). After PO Balb/c, inflammatory interleukin (IL)-2 and interferon gamma mRNA and protein were increased in 2C spleen cells, whereas they were decreased in 2C MLN. Anti-inflammatory cytokine IL-4 and IL-10 mRNA and protein were increased in 2C MLN after PO Balb/c, whereas they were not detectable in 2C spleen cells.

CONCLUSIONS

Systemic oral tolerance can be induced in B6 mice, whereas only regional mesenteric lymph node tolerance develops in transgenic 2C mice. The inability to induce systemic oral tolerance in 2C mice appears to be due to a significant increase in peripheral (splenic) CD4+ T cells.

Influence of gadolinium-induced kupffer cell blockade on portal venous tolerance in rat skin allograft transplantation

BACKGROUND

Intraportal injection of donor antigens delays rejection of allografts (portal venous tolerance). The study aimed to investigate the possible influence of prior gadolinium chloride (Gd)-induced Kupffer cell blockade on tolerance to non-vascularized skin allografts induced by means of donor-specific intraportal blood transfusion.

MATERIALS AND METHODS

Wistar rats (n = 10) were used as donors and Sprague-Dawley rats (n = 70) as recipients of a non-vascularized skin graft. Recipients were divided into groups according to the manipulations prior to transplantation, as follows: (1) no manipulation; (2) donor-specific intrajugular blood transfusion; (3) donor-specific intraportal blood transfusion; (4) Gd administration and donor-specific intrajugular blood transfusion; (5) Gd administration and donor-specific intraportal blood transfusion; (6) Gd administration, and (7) intraportal saline infusion. In a first set of experiments, these manipulations were performed once. In a second set of experiments, the same manipulations were performed twice. Skin allograft was performed 7 days after the last manipulation in all groups.

RESULTS

Group 3 showed the highest skin graft survival, particularly after repeated blood transfusion. Graft survival in this group was significantly higher than in any other group. Conversely, group 5 showed the lowest graft survival, particularly after repeated blood transfusion. Graft survival in this group was significantly lower than that of groups 1, 2, 3 and 7.

CONCLUSIONS

In this model of skin allograft transplantation, Gd administration abrogates and can even reverse the tolerogenic effect of repeated donor-specific intraportal blood transfusion.

Liver sinusoidal endothelial cells are insufficient to activate T cells

Liver sinusoidal endothelial cells (LSEC) have been reported to express MHC class II, CD80, CD86, and CD11c and effectively stimulate naive T cells. Because dendritic cells (DC) are known to possess these characteristics, we sought to directly compare the phenotype and function of murine LSEC and DC. Nonparenchymal cells from C57BL/6 mice were obtained by collagenase digestion of the liver followed by density gradient centrifugation. From the enriched nonparenchymal cell fraction, LSEC (CD45(-)) were then isolated to 99% purity using immunomagnetic beads. Flow cytometric analysis of LSEC demonstrated high expression of CD31, von Willebrand factor, and FcgammaRs. However, unlike DC, LSEC had low or absent expression of MHC class II, CD86, and CD11c. LSEC demonstrated a high capacity for Ag uptake in vitro and in vivo. Although acetylated low-density lipoprotein uptake has been purported to be a specific function of LSEC, we found DC captured acetylated low-density lipoprotein to a similar extent in vivo. Consistent with their phenotype, LSEC were poor stimulators of allogeneic T cells. Furthermore, in the absence of exogenous costimulation, LSEC induced negligible proliferation of CD4(+) or CD8(+) TCR-transgenic T cells. Thus, contrary to previous reports, our data indicate that LSEC alone are insufficient to activate naive T cells.