P. J. Morris

CD40-CD40 ligand-independent activation of CD8+ T cells can trigger allograft rejection.

In experimental transplantation, blockade of CD40-CD40 ligand (CD40L) interactions has proved effective at permitting long-term graft survival and has recently been approved for clinical evaluation. We show that CD4+ T cell-mediated rejection is prevented by anti-CD40L mAb therapy but that CD8+ T cells remain fully functional. Furthermore, blocking CD40L interactions has no effect on CD8+ T cell activation, proliferation, differentiation, homing to the target allograft, or cytokine production. We conclude that CD40L is not an important costimulatory molecule for CD8+ T cell activation and that following transplantation donor APC can activate recipient CD8+ T cells directly without first being primed by CD4+ T cells.

REVERSIBILITY OF CYCLOSPORIN NEPHROTOXICITY AFTER THREE MONTHS' TREATMENT

86 renal allograft recipients were randomly assigned to cyclosporin (Cy) for 90 days followed by azathioprine and prednisolone (Aza and P), or to Aza and P from day 0, as part of the second Oxford trial of short-term Cy use. All 62 patients whose grafts functioned for at least 120 days were included in this study. Serum creatinine was significantly higher in Cy-treated patients than in control patients from day 28 to day 90. Serum uric acid was also significantly higher in Cy-treated patients over the same period. Both creatinine and uric acid fell to the level of the control group after conversion to Aza and P. Serum uric acid was significantly higher for a given level of creatinine during Cy treatment than in either the control patients or the Cy-treated patients after their treatment had been changed to Aza and P. These data imply that Cy affects both the glomerular filtration rate and renal tubular function but that these effects are largely reversible.

POWERFUL EFFECT OF HL-DR MATCHING ON SURVIVAL OF CADAVERIC RENAL ALLOGRAFTS

Matching for HLA-DR antigens seems to be an effective method of improving the survival rate of cadaveric donor renal allografts; this was shown in the analysis of 190 cadaver transplants in one unit. Patients receiving kidneys well-matched for HLA-DR (no incompatibilities) had a significantly better survival rate (85% at 1 year) than patients with 1 or 2 incompatibilities (64% and 56% respectively, at 1 year). This high survival rate of the DR matched grafts was not due to coincidental better matching of the HLA-A and B antigens. DR matching seems to improve graft survival even in patients who have never been transfused or not. Matching for the limited number of DR antigens mostly with a relatively high antigen frequency should simplify the matching procedure for selection of donor-recipient pairs in cadaveric transplantation.

LOW-DOSE ORAL PREDNISOLONE IN RENAL TRANSPLANTATION

Azathioprine and steroids (prednisone or prednisolone) form the basis of conventional immunosuppression after renal transplantation. Most of the morbidity in the early months after transplantation. Most of the attributed to steroids, which are normally give in high doses. The only justification for giving high doses is a historical one. For this reason a randomised controlled trial was carried out to compare the efficacy of high dose (39 patients) and low dose (33 patients) oral prednisolone, both in combination with azathioprine, in patients given cadaveric renal allografts. Patients were followed up for at least two years after the transplantation. Patient and graft survival were identical in the two groups and the morbidity associated with steroids was impressively lower in patients receiving a low steroid dose. Although the optimal dose of steroids is still unknown, there seems little justification for continued use of high doses of oral steroids with azathioprine after cadaveric renal transplantation.

CYCLOSPORIN CONVERSION VERSUS CONVENTIONAL IMMUNOSUPPRESSION: LONG-TERM FOLLOW-UP AND HISTOLOGICAL EVALUATION

129 patients who received a cadaver renal transplant entered a randomised prospective trial of cyclosporin for 3 months with conversion to azathioprine and prednisolone compared with conventional therapy of azathioprine and prednisolone. In the 64 patients who received cyclosporin, actuarial patient survival was 92%, and actuarial graft survival was 72% and 67% at 1 and 4 years after transplantation. Graft survival was significantly better (p less than 0.03) than in the 65 patients who received conventional therapy, in whom actuarial patient survival was 94%, and actuarial graft survival was 59% and 47% at 1 and 4 years. Renal function and other side-effects improved quickly after conversion with the better renal function maintained throughout follow-up. Renal biopsies at 90 days and 1 year in all patients did not show consistent improvement after conversion from cyclosporin in the histological features that might be attributable to cyclosporin toxicity. After conversion, 32% of the patients had acute rejection, generally within 30 days. 1 graft was lost to early acute rejection after conversion and another was lost 3 months later from acute-on-chronic rejection. A total of 8 grafts were lost to chronic rejection in the cyclosporin-treated group and 6 in the conventional group. The improvement in renal function obtained with this protocol of short-term cyclosporin with conversion to azathioprine and prednisolone has to be balanced against the risk of acute rejection and even loss of the graft after conversion.

Mechanisms of Allograft Rejection: The Roles of Cytotoxic T‐Cells and Delayed‐Type Hypersensitivity

Despite studies extending over 4 decades, the mechanisms undelying graft rejection remain poorly understood. This is not to imply that such studies have proved unfruitful, as they have led to the discovery of the major histocompatibility complex (MHC) (Gorer et al. 1948), the clonal deletion theory of self tolerance (Burnett & Fenner 1949, Billingham et al. 1956), and the importance of the lymphocyte in mediating immune reactions (Gowans 1970). A further major advance in understanding the cellular basis of allograft rejection came with the demonstration of the importance of thymus-derived (T) cells in graft rejection (Miller 1962), but because a wide range of effector mechanisms have been shown to depend on the helper or inducer activity of T-cells these may be implicated in allograft rejection in a number of ways (Mason 1983). The formation of alloantibody, the differentiation of cytotoxic T-(Tc)-celIs, the activation of macrophages and at least some natural killer cells (NK) from inactive precursors require the participation of a subset oi T-cells (Th) with helper activity, and recent work has concentrated on trying to identify which of the possible T-celldependent processes are required for graft rejection to occur.

PEROPERATIVE BLOOD-TRANSFUSIONS IMPROVE CADAVERIC RENAL-ALLOGRAFT SURVIVAL IN NON-TRANSFUSED RECIPIENTS: A Prospective Controlled Clinical Trial

Abstract The effect of peroperative transfusion was studied in 27 patients who had never had a blood-transfusion or been pregnant and who were receiving their first cadaver renal allograft. 13 patients in the treatment group were given 2 units of whole stored blood at transplantation, whereas 14 patients in the control group were given no blood. Actuarial analysis after 2 years showed a graft survival of 85% at 1 year in the treated group compared with 34% at 1 year in the control group (p=0.03). Transfusion of non-transfused patients during transplantation may be as effective as pregraft transfusion.

T-cell activation, proliferation, and memory after cardiac transplantation in vivo.

OBJECTIVE To study the response of alloantigen (H2Kb)-specific T cells to a H2b+ cardiac allograft in vivo. SUMMARY BACKGROUND DATA The response of T cells to alloantigen has been well characterized in vitro but has proved more difficult to assess in vivo. The aim of these experiments was to develop a model of T-cell-mediated rejection where the response of T cells after transplantation of a cardiac allograft could be followed in vivo. METHODS Purified CD8+ T cells from H2Kb-specific TCR transgenic mice (BM3; H2k) were adoptively transferred into thymectomized, T-cell-depleted CBA/Ca (H2k) mice. These mice were then transplanted with a H2Kb+ cardiac allograft. Using four-color flow cytometry, the proliferative response, modulation of activation markers, and potential cytokine production of the H2Kb-specific T cells was assessed after transplantation. RESULTS Consistent rejection of H2Kb+ cardiac allografts required the transfer of at least 6 x 10(6) CD8+ H2Kb-specific T cells. Short-term analyses revealed that the transgenic-TCR+/ CD8+ T cells proliferated and became activated after transplantation of an H2Kb+ cardiac allograft. Fifty days after transplantation, the transgenic-TCR+/CD8+ T cells remained readily detectable, bore a predominantly memory phenotype (CD44hi), and rapidly produced interleukin 2 and interferon-gamma on in vitro restimulation. CONCLUSIONS These data show that the activation of alloantigen-specific T cells can be followed in vivo in short-term and long-term experiments, thereby providing a unique opportunity to study the mechanisms by which T cells respond to allografts in vivo.

Studies of HLA-DR with Relevance to Renal Transplantation*

The serological determination of leukocyte antigens in man which began some 20 years ago, and their subsequent recognition as histocompatibility antigens, led to immediate interest in the possible application of leukocyte typing for matching of donors and recipients of organ grafts. As the genetic control of these antigens gradually was elucidated, it was apparent that the antigens detected in the late sixties could be divided into two series of allelic antigens. The two series of the major histocompatibility complex (MHC) in man, first designated HL-A, but later to become HLA, were shown to be genetically controlled by two loci on chromosome 6. Over the next 10 years extensive studies of matching for HLA, both in living related and in cadaver transplantation, were performed in an attempt to improve the success of renal transplantation. There is no question that within a family genotyping for HLA allows a precise determination of HLA identity, or otherwise, of the potential donor and recipient. Furthermore the outcome of intrafamilial renal allografts is very much in accord with the genetic disparity in HLA between donor and recipient. However, in cadaver renal transplantation after initial encouraging reports of a correlation between matching for a limited number of HLA antigens and cadaveric graft outcome (Morris et al. 1968, Patel et al. 1968) reports began to appear showing little or no correlation, especially from the pioneer laboratory in the field, that of Terasaki (Mickey et al. 1971). Controversy about the role of matching for HLA-A,B in cadaver transplantation raged over the next 8 years or so, but by the mid-seventies some degree of consensus was reached, namely that grafts well matched for HLA-A,B showed about a 10-20% better graft survival at I year than poorly matched grafts. (Morris et al. 1978a).

Intragraft interleukin-4 mRNA expression after short-term CD154 blockade may trigger delayed development of transplant arteriosclerosis in the absence of CD8+ T cells

Background. It has recently been shown that, although anti-CD154 induces CD4+ T-cell tolerance, it is unable to prevent allograft rejection mediated by CD8+ T cells. We have also shown that anti-CD154 monotherapy does not protect the graft from the development of transplant arteriosclerosis even in the absence of CD8+ T cells. This study was designed to investigate and characterize possible mechanisms responsible for the development of transplant arteriosclerosis after CD154 blockade in the absence of CD8+ T cells. Methods. C57BL/6 (H2b) recipients received a fully MHC-mismatched BALB/c donor aorta (H2d). Animals were either treated with anti-CD154 monoclonal antibody (mAb) in the presence or absence of CD8 T cells. Histology, morphometric measurements, immunohistochemistry, and the production of alloantibodies (IgM, IgG1, IgG2a) were analyzed on days 14, 30, and 50 after transplantation. Cytokine production within the graft was investigated by competitive reverse transcription-polymerase chain reaction on day 14. Results. Combined treatment with anti-CD154 and a depleting CD8 mAb resulted in a delay in the development of transplant arteriosclerosis (intimal proliferation: 33±10% vs. 67±11% untreated control, day 30) but ultimately did not prevent its progression (intimal proliferation: 55±10% vs. 78±9% untreated control, day 50). Although there was a significant decrease in the number of CD4+, CD11b+, and CD40+ graft-infiltrating cells and a reduction in the formation of donor-specific IgG1 alloantibodies in recipients treated with anti-CD154 and anti-CD8 mAbs, mRNA for interleukin (IL)-4 was increased, suggesting a shift in the intragraft cytokine profile towards a Th2-like pattern. Conclusions. Our data provide evidence that short-term CD154 blockade is insufficient to prevent transplant arteriosclerosis, even in combination with CD8+ T-cell depletion. Moreover, the increased expression of the Th2 cytokine interleukin-4 within the graft may be responsible for the development of transplant arteriosclerosis in the long term.