Triazolopyrimidine derivative NK026680 and donor-specific transfusion induces CD4+CD25+Foxp3+ T cells and ameliorates allograft rejection in an antigen-specific manner

We have previously demonstrated the unique properties of a new triazolopyrimidine derivative, NK026680, which exerts immunosuppressive effects in rat heart transplant model and confers tolerogeneic properties on ex vivo-conditioned dendritic cells in mice. We herein demonstrate that NK026680 promotes the expansion of regulatory T cells (Tregs) with potent immunoregulatory effects when used in combination with donor-specific transfusion (DST).BALB/c (H-2^d) heart graft were transplanted into C57BL/6 (H-2^b) mice following intravenous injection of donor splenocytes (DST) and oral administration of NK026680. The NK026680 plus DST treatment markedly prolonged the survival time of the donor-graft, but not that of the 3rd party-graft (C3H; H-2^k). Treg cells in the recipient spleen on day 0 expanded when stimulated with donor-antigens in vivo and in vitro. After heart transplantation, Treg cells accumulated into the graft and increased in the spleen. NK026680 plus DST also decreased activated CD8⁺ T cells in the spleen and inhibited infiltration of CD8⁺ T cells into the graft. Depletion of CD25⁺ cells inhibited the graft prolonging effect of the NK026680 plus DST treatment.NK026680 administration together with DST induces potent immunoregulatory effects in an antigen-specific manner, likely due to the in vivo generation of donor-specific Tregs.     

A novel chemical compound, NK026680, targets dendritic cells to prolong recipient survival after rat liver grafting

BACKGROUND: There is great interest in the recently developed immunosuppressant NK026680, which is a derivative of triazolopyrimidine. Its unique chemical structure and action mechanism are completely different from those of conventional immunosuppressants. METHODS: The present study was designed to investigate the effects of NK026680 on rat bone-marrow-derived dendritic cell (BMDC) differentiation and maturation in an in vitro culture system and its applicability in liver transplantation. RESULTS: NK026680 inhibited T-cell proliferation stimulated by alloantigen in a dose-dependent manner, but did not inhibit concanavalin A. The populations of OX6+CD161a cells and CD86+CD161a cells were suppressed in NK026680-treated dendritic cells (DCs). Exposure of DCs to NK026680 downregulated the interleukin (IL)-12 (p40, p35), interferon-gamma mRNA expression and upregulated IL-10, transforming growth factor-beta, in which impaired the ability of DC to stimulate T cell proliferation. Furthermore, oral administration of NK026680 for 14 days significantly prolonged liver allograft survival and limitation of T-cell responses and polarization toward a Th2 cytokine profile. CONCLUSIONS: These results demonstrate that NK026680 may have therapeutic potential for preventing allo-rejection in organ transplantation, acting at the step of immune response through inhibiting BMDC differentiation and maturation into potent antigen-presenting cells.     

Exercise increases skin graft resistance to rejection

Regular exercise reduces risk of various chronic diseases and can prevent the development and recurrence of cancer, making it a promising nonpharmacological modulator of disease. Yet the effect of regular exercise on solid organ transplant outcome remains uncertain. Using a model of voluntary wheel‐running exercise and skin transplantation in mice, we hypothesized that exercise strengthens the alloimmune response, leading to an increased rate of rejection. Instead, we found that regular exercise in mice resulted in prolonged graft survival, with mean allograft survival time increasing by almost 50%. We observed this graft survival extension in exercised mice despite evidence of a slightly enhanced alloimmune response, comprised of increased proliferation of alloreactive CD4⁺ T cells, as well as increased interferon‐γ production by these cells. Exercise was not associated with significant changes in numbers of conventional CD4⁺ or CD8⁺ T cells, NK cells, or Foxp3⁺ regulatory T cells. In conclusion, our study suggests that exercise increases skin graft resistance to a similar or slightly higher level of alloimmunity and supports regular exercise as an important beneficial pursuit for transplant recipients.     

Immunosuppressive Activity of Adipose Tissue-Derived Mesenchymal Stem Cells in a Rat Model of Hind Limb Allotransplantation

Many reports have shown that bone marrow–derived mesenchymal stem cells exhibit immunosuppressive effects in allogeneic transplantation. However, few reports have evaluated the immunosuppressive properties of adipose tissue–derived mesenchymal stem cells (ASCs) in vitro and in vivo. In this study, we investigated the immunosuppressive characteristics of ASCs, and investigated whether ASCs originating from donor rats prolong allotransplant survival in a rat hind limb allotransplantation model. T-cell proliferation stimulated by allogeneic stimuli or mitogen with or without ASCs originating from the donor was assessed in vitro. The effects of cellular contact or soluble factors on the inhibition of T-cell proliferation were also evaluated. In the in vivo study, cultured ASCs (1 × 10⁵) that originated from the donor were injected into recipient animals intravenously immediately after operation, followed by 1 dose per day for 3 consecutive days post-transplantation. When immune rejection occurred, the survival time of allotransplants was determined and rejected tissue was histologically and immunochemically assessed for determining regulatory T-cell infiltration. ASCs inhibited the T-cell proliferation stimulated by alloantigen or mitogen in a dose-dependent manner, and recipient T cells proliferated less in animals treated with ASCs than in controls. Although ASCs were separated from T cells, ASCs persisted to elicit a suppressive effect. ASC culture supernatants did not inhibit T-cell proliferation; however, supernatants obtained from the mixed lymphocyte reaction in the presence of ASCs suppressed T-cell proliferation. ASCs prolonged allotransplant survival time, reduced inflammatory cell infiltration, and induced regulatory T cells. In conclusion, ASCs can exhibit in vitro immunosuppressive properties and prolong allotransplant survival time in a rat hind limb composite tissue allotransplantation model, possibly through the induction of regulatory T cells.     

Mechanism of the immunosuppressive effect in vivo of novel immunosuppressive drug β-SQAG9, which inhibits the response of the CD62L T-cell subset

Introduction

We synthesized sulfo-glycolipid, β-SQAG9 (designate □ β-SQAG9 liposome, because it efficiently forms a liposome structure) that possessed immunosuppressive effects such as inhibition of T-cell responses in human allogeneic MLR and skin allograft survival in rats, and bound to CD62L (L-selectin) in vitro. In this study, we further investigated the immunosuppressive mechanism in vivo by β-SQAG9 liposome in a skin-allografted rat model.

Methods

ACI rats (RT1^a) were grafted skin of LEW rats (RT1¹) treated with PBS or β-SQAG9 liposome IV once a day for 7 days. Subsequently, we investigated the population of T cells and CD62L⁺ T-cell subset in the spleen, axillary lymph nodes (ALNs), and peripheral blood of skin-allografted rats by two-color flow cytometry.

Results

Five of 11 (45.5%) rats that were treated with 50 mg/kg β-SQAG9 liposome showed graft survival and another showed moderate rejection in graft. The CD62L⁺ T-cell subset population in ALNs of β-SQAG9 liposome-treated rats decreased in a dose-dependent manner. No significant difference in the T-cell population was observed between the β-SQAG9 and control groups. These data suggest that β-SQAG9 could bind to the CD62L⁺ T-cell subset in vivo as well as in vitro and affect T-cell migration, which might lead to T-cell tolerance in vivo.     

Synergistic immunosuppressive effects of rosmarinic acid and rapamycin in vitro and in vivo

BACKGROUND: We previously demonstrated that rosmarinic acid (RosA) inhibits T-cell antigen receptor-induced T-cell activation and proliferation. In this study, we evaluated the ability of RosA alone and in conjunction with currently used immunosuppressive drugs to inhibit in vitro splenic T-cell proliferation and prolong skin graft survival in vivo. METHODS: Mouse splenic T-cell proliferation assays were performed in the presence of RosA alone or in combination with cyclosporine, rapamycin (Rapa), or prednisone (Pred). The in vivo synergistic efficacy of RosA and Rapa was evaluated in the mouse skin allograft model. RESULTS: RosA combined with Rapa or prednisone synergistically inhibited splenic T-cell proliferation, whereas the combination of RosA and cyclosporine additively inhibited T-cell proliferation. The combination of RosA and Rapa synergistically prolonged allograft survival. CONCLUSIONS: We conclude that the combination of RosA and Rapa promotes immunosuppressive effects.     

Distribution of intrahepatic T, NK and CD3(+)CD56(+)NKT cells alters after liver transplantation: Shift from innate to adaptive immunity?

Background

The liver is an immunological organ containing a large number of T, NK and NKT cells, but little is known about intrahepatic immunity after LTx. Here, we investigated whether the distribution of T, NK and CD3⁺CD56⁺NKT cells is altered in transplanted livers under different circumstances.

Methods

Core biopsies of transplanted livers were stained with antibodies against CD3 and CD56. Several cell populations including T (CD3⁺CD56^-), NK (CD3^-CD56⁺) and NKT cells (CD3⁺CD56⁺) were studied by fluorescence microscopy. Cell numbers were analyzed in relation to the time interval after LTx, immunosuppressive therapy and stage of acute graft rejection (measured with the rejection activity index: RAI) compared to tumor free liver tissue from patients after liver resection due to metastatic disease as control.

Results

Recruitment of CD3⁺CD56⁺NKT cells revealed a significant decrease during high RAI scores in comparison to low and middle RAI scores (RAI 7-9: 0.03 ± 0.01/HPF vs. RAI 4-6: 0.1 ± 0.005/HPF). CD3⁺CD56⁺NKT cells were also lower during immunosuppressive therapy with tacrolimus (0.03 ± 0.01/HPF) than with cyclosporine (0.1 ± 0.003/HPF), cyclosporine/MMF (0.1 ± 0.003/HPF) or sirolimus (0.1 ± 0.01/HPF) treatment. Intrahepatic T cell numbers increased significantly 50 days after LTx compared to control liver tissue (4.5 ± 0.2/HPF vs. 1.9 ± 0.1/HPF). In contrast, NK cells (0.3 ± 0.004/HPF) were significantly fewer in all biopsies after LTx compared to the control (0.7 ± 0.04/HPF).

Conclusions

These data indicate significant alterations in the hepatic recruitment of T, NK and CD3⁺CD56⁺NKT cells after LTx. The increase in T cells and the decrease in NK and CD3⁺CD56⁺NKT cells suggest a shift from innate to adaptive hepatic immunity in the liver graft.     

Accumulation of High Levels of Monocytic Myeloid-Derived Suppressor Cells Enhances Graft Survival in Almost-Tolerant Kidney Transplant Recipients

Background

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature cells that suppress immune responses during organ transplantation and participate in mediating long-term graft survival and immune tolerance in animal transplant models. However, their role in regulating transplant tolerance in human subjects is not well understood. In the present study, we investigated the role of MDSCs in mediating long-term graft survival in almost-tolerant kidney transplant recipients (ATKTRs) and the mechanism(s) responsible for increasing MDSC numbers in these recipients.

Changes in blood ketone body ratio with reference to graft viability after liver transplantation in rats

Arterial blood ketone body ratio (acetoacetate/3-hydroxybutyrate; KBR), which reflects hepatic mitochondrial redox potential, was measured during a 2-week period after orthotopic liver transplantation in three groups of rats: group 1, the isogenic combination of LEW (RT1¹) graft to LEW recipient as control; group 2, the allogenic combination of ACI (RT1^a) graft to LEW recipient without immunosuppressive treatment; and group 3, the allogenic combination of ACI to LEW with immunosuppressive treatment using cyclosporin (CyA). Isogenic recipients survived indefinitely. Allogenic recipients in group 2 had severe rejection with a mean survival of 10.3±0.54 days, while 77.8% of the allogenic recipients in group 3 survived more than 30 days. KBR of rats surviving more than 2 weeks in groups 1 and 3 gradually increased post-transplantation and was maintained at a high level. By contrast, though KBR in group 2 was restored at 3 days, it gradually fell and remained at a significantly low level (P<0.001). It is suggested that KBR provides an accurate indicator for evaluating metabolic viability of the critically deteriorating liver graft accompanied by severe rejection.     

A New Look at Blockade of T-cell Costimulation: A Therapeutic Strategy for Long-term Maintenance Immunosuppression

Activated T cells orchestrate the immune response that results in graft rejection; therefore, a common goal among current immunosuppressive therapies is to block T-cell activation, proliferation and function. Current immunosuppressive regimens that inhibit T cells and immune cells have greatly reduced the incidence of acute rejection following solid-organ transplant. However, the expected improvements in long-term outcomes have not been realized. This may be related to the non-immune side effects of current maintenance immunosuppressants, which target ubiquitously expressed molecules. The focus in transplantation research is shifting in search of maintenance immunosuppressive regimens that might offer improved long-term outcomes by providing efficacy in prevention of acute rejection combined with reduced toxicities. An emerging therapeutic strategy involves an immunoselective maintenance immunosuppressant that inhibits full T-cell activation by blocking the interaction between costimulatory receptor–ligand pairs. This review describes costimulatory pathways and the development of molecules, which inhibit them in the context of transplantation research. Recent clinical data using the selective costimulation blocker, belatacept (LEA29Y), as a part of a CNI-free maintenance immunosuppressive regimen in renal transplantation is highlighted.     

Mechanism of the immunosuppressive effect in vivo of novel immunosuppressive drug beta-SQAG9, which inhibits the response of the CD62L+ T-cell subset

INTRODUCTION: We synthesized sulfo-glycolipid, beta-SQAG9 (designate square beta-SQAG9 liposome, because it efficiently forms a liposome structure) that possessed immunosuppressive effects such as inhibition of T-cell responses in human allogeneic MLR and skin allograft survival in rats, and bound to CD62L (L-selectin) in vitro. In this study, we further investigated the immunosuppressive mechanism in vivo by beta-SQAG9 liposome in a skin-allografted rat model. METHODS: ACI rats (RT1(a)) were grafted skin of LEW rats (RT1(1)) treated with PBS or beta-SQAG9 liposome IV once a day for 7 days. Subsequently, we investigated the population of T cells and CD62L(+) T-cell subset in the spleen, axillary lymph nodes (ALNs), and peripheral blood of skin-allografted rats by two-color flow cytometry. RESULTS: Five of 11 (45.5%) rats that were treated with 50 mg/kg beta-SQAG9 liposome showed graft survival and another showed moderate rejection in graft. The CD62L(+) T-cell subset population in ALNs of beta-SQAG9 liposome-treated rats decreased in a dose-dependent manner. No significant difference in the T-cell population was observed between the beta-SQAG9 and control groups. These data suggest that beta-SQAG9 could bind to the CD62L(+) T-cell subset in vivo as well as in vitro and affect T-cell migration, which might lead to T-cell tolerance in vivo.     

Profiles of B-cell subsets in immunologically stable renal allograft recipients and end-stage renal disease patients

BackgroundPost-transplantation pharmacotherapies typically employ combinations of immunosuppressive agents that have been designed for targeted inhibition of T-cells and T-cell subsets. Studies of acute and chronic effects of clinically employed immunosuppressive agents on B-cells and B-cell subsets are significantly fewer in number and warrant further investigation. Accordingly, the goal of the present cross-sectional study is to functionally evaluate differences of B-cell subsets in patients with end-stage renal disease (ESRD) and immunologically stable renal transplant patients.Patients and methodsOf 103 patients who underwent renal transplantation, 73 patients were immunologically stable without rejection or infection. Among them, 34 patients were one-year post-transplantation, and 39 patients were five-year post-transplantation. The study also included 35 ESRD patients and 36 healthy volunteers. Flow cytometry identified B-cell subsets in the study groups.ResultsRenal allograft recipients had reduced percentages of total B-cells (CD19+) and regulatory B-cells (B_reg) (CD38^highCD27 + CD24+) compared with healthy controls. The percentage of transitional B-cells (IgM + CD38^highCD24^high) and marginal zone (MZ) B-cells (IgD-CD27+) was reduced in transplant recipients compared with patients with ESRD and healthy volunteers. The highest percentage of plasma cells (PCs) (CD38^highCD27 + CD24-) was in patients with ESRD. In five-year post-transplantation group, CD38^lowCD21- B-cells increased when compared with the other groups. Healthy volunteers and patients with ESRD had fewer unswitched memory (UM) B-cells (IgM + IgD + CD38^lowCD27+), and increased isotype switched memory (ISM) B-cells (IgM-IgD-CD38^lowCD27+). There was no difference in the percentage of naïve B-cells (IgD + CD27-) among diverse groups.ConclusionsThe percentages of the total, transitional, B_reg, PCs, MZ, and UM B-cell subsets in immunologically stable renal allograft recipients were significantly different from healthy controls. However, B-cell subsets in patients with ESRD were minimally different with immunologically stable renal allograft recipients.     

New insights into the interactions between T-cell costimulatory blockade and conventional immunosuppressive drugs

OBJECTIVE: To determine the precise in vivo interaction between T-cell costimulatory blockade and conventional immunosuppression in transplantation. SUMMARY BACKGROUND DATA: Blocking B7 or CD154 T-cell costimulatory activation pathways prevents allograft rejection in small and large animal transplant models and is considered a promising strategy for clinical organ transplantation. METHODS: A fully MHC-mismatched vascularized mouse cardiac allograft model was used to test the interactions between anti-CD154 or CTLA4Ig monotherapy and conventional immunosuppressive drugs in promoting long-term graft acceptance. The frequency of alloreactive T cell was measured by ELISPOT. Chronic rejection was examined by histology. RESULTS: Cyclosporine, tacrolimus, and anti-IL-2R monoclonal antibody therapy abrogated the effect of a single-dose protocol of anti-CD154 therapy. In contrast, rapamycin acted synergistically with anti-CD154 therapy in promoting long-term allograft survival. The addition of calcineurin inhibitors did not abolish this synergistic effect. Intense CD154-CD40 blockade by a multiple-dose schedule of anti-CD154 resulted in long-term graft survival and profound alloreactive T-cell unresponsiveness and overcame the opposite effects of calcineurin inhibitors. CTLA4Ig induced long-term graft survival, and the effect was not affected by the concomitant use of any immunosuppressive drugs. CONCLUSIONS: The widespread view that calcineurin inhibitors abrogate the effects of T-cell costimulatory blockade should be revisited. Sufficient costimulatory blockade and synergy induced by CD154 blockade and rapamycin promote allograft tolerance and prevent chronic rejection.     

Role of NK and NKT cells in solid organ transplantation

In the context of solid organ transplantation, the exact interactions between the innate and adaptive alloimmune response have not yet been fully explored. In this transplant setting, natural killer (NK) cells have emerged as a particular focus of interest because of their ability to distinguish allogeneic major histocompatibility complex (MHC) antigens and their potent cytolytic activity. Based on this observation and its potential clinical relevance, NK cells have recently been shown to participate in the immune response in both acute and chronic rejection of solid organ allografts. Numerous experimental and clinical studies demonstrate that NK cells determine transplant survival by rejecting an allograft not directly but indirectly by providing bystander effects. In addition, NK cells are influenced by immunosuppressive therapies such as calcineurin inhibitors or steroids. As NK and natural killer T (NKT) cells have also been shown to play a profound role in allograft tolerance induction, this review summarizes the major findings to highlight the functional role of these lymphocyte subsets, which may constitute an underestimated mechanism affecting graft outcome in solid organ transplantation.     

Long-term survival of limb allografts induced by pharmacologically conditioned, donor alloantigen-pulsed dendritic cells without maintenance immunosuppression

BACKGROUND: We showed recently that limb allograft survival could be enhanced by administration of alloantigen (Ag)-pulsed immature dendritic cells (DC) after transplantation. Since indefinite graft survival was not achieved, we have further modified the DC by pharmacologic (rapamycin; Rapa) conditioning and ascertained their influence on graft survival, without continued immunosuppressive therapy. METHODS: We compared the ability of donor Ag-pulsed, Rapa-conditioned rat myeloid DC (Rapa DC) and control DC (CTR DC) to inhibit alloreactive T-cell responses after limb transplantation in antilymphocyte serum (ALS)-treated recipients given a short postoperative course of cyclosporine (CsA). RESULTS: Both DC populations expressed similar levels of major histocompatibility complex (MHC) II, CD40 and CD54, but Rapa DC expressed lower CD86. After toll-like receptor activation, both populations produced minimal interleukin (IL)-12p70, but Rapa DC secreted lower levels of IL-6 and IL-10. The capacity of DCs to stimulate T-cell proliferation in mixed leukocyte reactions was very low. Pulsing of the DC with donor Ag did not alter their phenotype or function. Interestingly, posttransplant administration of donor Ag-pulsed Rapa DC to rats given perioperative ALS and 21 days CsA significantly delayed graft rejection and promoted long-term (>125 days) graft survival. AlloAg-pulsed Rapa DC induced T-cell hyporesponsiveness and promoted the generation of IL-10-secreting CD4 T cells upon ex vivo challenge. CONCLUSIONS: Infusion of donor Ag-pulsed, Rapa-conditioned DC after composite tissue transplantation can prevent rejection of the grafts, including skin, across a full MHC mismatch and in the absence of continued immunosuppressive therapy.     

Transplant immunology

The immune response to an allogeneic transplanted organ is T-cell dependent. It is governed partially by the context in which the T-cell encounters the antigen and can range from apoptosis, anergy, and neglect to full activation. The current armamentarium of immunosuppressive agents acts to inhibit the various steps of this T-cell activation pathway; at the level of the T-cell receptor (monoclonal antibodies such as OKT3), intracellular signally (calcineurine-inhibitors), DNA synthesis (azathioprine), or to cause lymphocyte depletion (ATG, ALG). Most protocols use a combination of agents for induction and maintenance immunosuppression. Although successful in preventing and treating allograft rejection, they are not without side effects. With improved patient and graft survival rates, adverse events such as hypertension, nephrotoxicity, hyperglycaemia, and lymphoproliferative disease become increasingly important issues. Newer drugs (IL-2 receptor antagonists, mycophenolate mofetil, rapamycin) have been introduced in an attempt to spare or avoid these adverse effects. Inducing graft tolerance and long-term drug-free survival is the goal of transplant immunologists. Postulated mechanisms include clonal deletion, anergy, and immunoredirection. Although a number of methods have been tested experimentally, none has been proven to induce tolerance for routine clinical use. Immunosuppression remains the cornerstone of the success of organ transplantation. Until investigators are able to induce tolerance in their transplant recipients or develop a tolerance assay, they would need to continue to tailor their immunosuppressive therapy according to the risk profile of the individual recipient.     

Age‐Dependent Metabolic and Immunosuppressive Effects of Tacrolimus

Immunosuppression in elderly recipients has been underappreciated in clinical trials. Here, we assessed age‐specific effects of the calcineurin inhibitor tacrolimus (TAC) in a murine transplant model and assessed its clinical relevance on human T cells. Old recipient mice exhibited prolonged skin graft survival compared with young animals after TAC administration. More important, half of the TAC dose was sufficient in old mice to achieve comparable systemic trough levels. TAC administration was able to reduce proinflammatory interferon‐γ cytokine production and promote interleukin‐10 production in old CD4⁺ T cells. In addition, TAC administration decreased interleukin‐2 secretion in old CD4⁺ T cells more effectively while inhibiting the proliferation of CD4⁺ T cells in old mice. Both TAC‐treated murine and human CD4⁺ T cells demonstrated an age‐specific suppression of intracellular calcineurin levels and Ca²⁺ influx, two critical pathways in T cell activation. Of note, depletion of CD8⁺ T cells did not alter allograft survival outcome in old TAC‐treated mice, suggesting that TAC age‐specific effects were mainly CD4⁺ T cell mediated. Collectively, our study demonstrates age‐specific immunosuppressive capacities of TAC that are CD4⁺ T cell mediated. The suppression of calcineurin levels and Ca²⁺ influx in both old murine and human T cells emphasizes the clinical relevance of age‐specific effects when using TAC.     

Anti-integrin (LFA-1, VLA-4, and Mac-1) antibody treatment and acute cardiac graft rejection in the rat

Cell adhesion molecules mediate interactions with other cells and extracellular matrix, control cell infiltration in sites of inflammation, and regulate cell activation. Previous studies have shown that treatment of rat cardiac transplant recipients with a combination of antibodies against the T-cell integrins LFA-1 and VLA-4 gave a modest prolongation of graft survival. Current experiments were designed to examine the effect of blocking Mac-1, an important monocyte adhesion receptor and mediator of monocyte migration, together with anti-LFA-1 and anti-VLA-4 antibodies on cardiac graft survival and on the graft rejection pattern. The anti-Mac-1, CD11b-specific antibody OX-42 did not affect graft survival time although it did decrease the graft infiltration by rounded, ED-2-positive macrophages.     

LFA‐1 Antagonism Inhibits Early Infiltration of Endogenous Memory CD8 T Cells into Cardiac Allografts and Donor‐Reactive T Cell Priming

Alloreactive memory T cells are present in virtually all transplant recipients due to prior sensitization or heterologous immunity and mediate injury undermining graft outcome. In mouse models, endogenous memory CD8 T cells infiltrate MHC‐mismatched cardiac allografts and produce IFN‐γ in response to donor class I MHC within 24 h posttransplant. The current studies analyzed the efficacy of anti‐LFA‐1 mAb to inhibit early CD8 T cell cardiac allograft infiltration and activation. Anti‐LFA‐1 mAb given to C57BL/6 6 (H‐2^b) recipients of A/J (H‐2^a) heart grafts on days –1 and 0 completely inhibited CD8 T cell allograft infiltration, markedly decreased neutrophil infiltration and significantly reduced intragraft expression levels of IFN‐γ‐induced genes. Donor‐specific T cells producing IFN‐γ were at low/undetectable numbers in spleens of anti‐LFA‐1 mAb treated recipients until day 21. These effects combined to promote substantial prolongation (from day 8 to 27) in allograft survival. Delaying anti‐LFA‐1 mAb treatment until days 3 and 4 posttransplant did not inhibit early memory CD8 T cell infiltration and proliferation within the allograft. These data indicate that peritransplant anti‐LFA‐1 mAb inhibits early donor‐reactive memory CD8 T cell allograft infiltration and inflammation suggesting an effective strategy to attenuate the negative effects of heterologous immunity in transplant recipients.     

Immunophenotypic Pattern of De Novo Malignancy After Liver Transplantation

Long-term survival after liver transplantation is affected by de novo neoplasia. The incidence of this type of malignancy is increased in the setting of immunosuppressive therapy. The aim of this study was to characterize the immunologic pattern of liver transplant recipients with de novo malignancies. Fifty-one liver recipients were studied, 19 of whom had a history of de novo neoplasia. Immunophenotypic patterns among patients with/without tumors were compared. The subpopulations of CD4⁺ T lymphocytes and CD8⁺ T lymphocytes differed between the 2 types of patients studied. In patients with tumor, activation membrane markers in CD4⁺ T lymphocytes and CD8⁺ T-lymphocytes, such as CD56 or CD25, were expressed in a greater proportion, whereas activation markers CD314 and CD16 were reduced in CD56^bright natural killer (NK) cells. We concluded that cytotoxic response seems to be more activated in de novo neoplasia patients, which highlights the still unknown malignancy risk effect on these immune cells.