Long-term results of solid organ transplantation. Report from the Eurotransplant International Foundation

Graft survival of cadaveric kidney-only, liver-only and heart-only transplants, performed in the Eurotransplant area between 1987-1990, was analysed, up to 5 years after transplantation. 1. HLA-A,-B,-DR mismatches had a statistically significant adverse influence on renal graft survival. 2. Kidney retransplantation was not found to be associated with a higher risk of graft loss, in contrast to liver and heart retransplantation. 3. The use of non-ideal donors (aged under 16 or over 55, non-head trauma donors) in renal transplantation should be re-evaluated, while elderly donors as well as elderly recipients jeopardized liver and heart transplant success rates. 4. A learning phase in liver and heart transplantation was evident from 1987-1990. 5. Time-effect studies can be used to adopt individual monitoring schemes. A persistent risk of graft loss in renal transplantation was observed for transplants from older donors and transplants in older recipients; these grafts constituted a very vulnerable group. For liver and heart retransplants it was noted that once patients had survived the first postoperative month, their relative risk of graft failure was no longer significantly different from patients with a first transplant. A well-considered long-term monitoring scheme for heart allograft recipients who are over age 55 is justified, as these patients had a higher risk of failure compared with younger patients. The same would be advantageous for liver transplants that are performed because of underlying liver malignancies.

Different patterns in donor-specific production of T-helper 1 and 2 cytokines by cells infiltrating the rejecting cardiac allograft

BACKGROUND

Cytokines play an important role in allograft rejection. The local production of cytokines by T-helper 2 cells within an allograft could influence the induction of graft rejection.

METHODS

Therefore we studied the in vitro production of cytokines by cells infiltrating the graft. graft-infiltrating cell cultures derived from human endomyocardial biopsy specimens more often produced interleukin-2 (p < 0.001), interferon-gamma (p < 0.001), interleukin-4 (p = 0.02), and interleukin-6 (p = 0.04) after stimulation with a B-cell line obtained from the heart donor than after stimulation with a third-party B-cell line. Furthermore, the levels of these cytokines were significantly higher after donor stimulation than after third-party stimulation (p < 0.001).

RESULTS

Within the first 90 days after heart transplantation, significantly higher levels of interleukin-2 (p = 0.050 and interferon-gamma (p = 0.02) were produced by donor-stimulated lymphocyte cultures derived from biopsy specimens taken during a rejection episode compared with cultures from biopsy specimens taken during a period without rejection. After 90 days, the levels of T-helper 1 cytokine (interleukin-2 and interferon-gamma) production were, irrespective of the rejection grade, comparable with those found in the cultures from rejection biopsy specimens taken early after transplantation. With regard to T-helper 2 cytokines (interleukin-4 and interleukin-6), no relation was found with the presence of rejection at any time after transplantation.

CONCLUSIONS

These data suggest that in the first 3 months after heart transplantation, acute rejection is associated with the production of increased levels of T-helper 1 cytokines but not of T-helper 1 cytokines but not of T-helper 2 cytokines by donor stimulated graft-infiltrating lymphocytes. Thereafter, the T-helper 1 cytokine production of graft-infiltrating lymphocytes remained high, suggesting a continuous state of immunologic activity even in the absence of rejection.

The action spectra for UV-induced suppression of MLR and MECLR show that immunosuppression is mediated by DNA damage

Ultraviolet-B (UVB, 280-320 nm) radiation can promote the induction of skin cancer by two mechanisms: damage of epidermal DNA and suppression of the immune system, allowing the developing tumor to escape immune surveillance. The mixed lymphocyte reaction (MLR) and the mixed epidermal cell lymphocyte reaction (MECLR) are commonly used methods to study the immunosuppressive effects of UVB radiation. To obtain a better understanding of the mechanism by which UVB radiation decreases the alloactivating capacity of in vitro-irradiated cells, action spectra for the MLR and MECLR were determined. Suspensions of peripheral blood mononuclear cells or epidermal cells were irradiated with monochromatic light of 254, 297, 302 or 312 nm and used as stimulator cells in the MLR or MECLR. Using dose-response curves for each wavelength, the action spectra were calculated. Both MLR and MECLR action spectra had a maximum at 254 nm and a relative sensitivity at 312 nm that was a thousand times lower than at 254 nm. Strikingly, the action spectra corresponded very closely to the action spectra that were found by Matsunaga et al. (Photochem. Photobiol. 54, 403-410, 1991) for the induction of thymine dimers and (6-4)photoproducts in irradiated calf thymus DNA solutions, strongly suggesting that the UV-induced abrogation of the MLR and MECLR responses is mediated by UV-induced DNA damage. Furthermore, the action spectra for the MLR and MECLR were similar, suggesting that they share a common mechanism for UV-induced suppression.

UVB-induced suppression of the mixed epidermal cell lymphocyte reaction is critically dependent on irradiance

The mixed epidermal cell lymphocyte reaction (MECLR) is a commonly used method to study the effects of ultraviolet B (UVB) radiation on the skin immune system. In UVB experiments dosimetry is very important. The influence of irradiance on the MECLR was studied in vitro using Philips FS40 lamps with variable UV intensities. Irradiation of isolated epidermal cells with high irradiance impaired the alloactivating capacity more than irradiation with low irradiance. In vivo, the influence of long-term UVB exposure on the MECLR was studied by treating normal healthy volunteers with suberythemagenic doses of UVB thrice weekly during 4 weeks. The first set of experiments, using low irradiance Sylvania UV-21 F75/85 W lamps, resulted in a decrease of MECLR responses of 83.1%. In the second set of experiments performed a year later, employing an identical protocol except for the use of high irradiance Waldmann UV-21 F85/100 W lamps, an increase of MECLR responses of 99.7% was observed. Volunteers of both sets of experiments received equal doses of UVB. In conclusion, this study shows that in vitro UVB-induced suppression of the MECLR is critically dependent on irradiance and therefore might explain contradictory results described in the literature. The in vivo data suggest that, comparable to the in vitro experiments, irradiance may influence the effects of UVB irradiation in vivo. Further experiments should prove whether this is indeed the case.

No evidence of an influence of the noninherited maternal HLA antigens on the alloreactive T cell repertoire in healthy individuals

In order to test whether a selective T cell nonresponsiveness to noninherited maternal human leukocyte antigens (NIM) exists, we measured the frequencies of alloreactive T cells of healthy individuals to their NIM HLA antigens and to their noninherited paternal (NIP) HLA antigens by limiting dilution assays. Both the frequencies of cytotoxic T cell precursors (CTLp) and IL-2-producing helper T cell precursors (HTLp) were determined. Similar frequencies were observed for NIM class I-reactive CTLp and NIP class I-reactive CTLp. This was the case when frequencies were determined against total NIM and NIP haplotypes but also when CTLp frequencies against individual NIM and NIP antigens were measured. A positive finding of this study was the confirmation of our earlier observation that CTLp frequencies against individual HLA-A antigens are generally lower than CTLp frequencies against HLA-B. This was found both for the maternal and the paternal HLA-A and -B antigens. Similarly, comparable frequencies of IL-2-producing helper T cell precursors directed against NIM HLA class II antigens and NIP HLA class II antigens were found. When breast-feeding in the neonatal period was considered, no differences in the frequencies of CTLp and HTLp were observed between children who had been breast-fed and children who had not. Therefore the present data do not support the hypothesis that confrontation with noninherited maternal HLA in neonatal life leads to down-regulation of alloreactive T cell responses to the mother.

The presence of activated donor HLA class I-reactive T lymphocytes is associated with rejection of corneal grafts

Although the cornea is considered to be an immunological privileged site, corneal transplantation can result in immunological rejection followed by graft failure, especially in patients with vascularized corneas. Several studies suggest a beneficial effect of matching for the HLA class I antigens on corneal graft survival, although a large study (the Collaborative Corneal Transplantation Study) failed to confirm this. To circumvent an endless discussion on studies either confirming or denying the relevance of HLA matching, we decided to approach this problem in another way. A more direct way to assess the importance of HLA class I antigens in corneal transplantation is to measure whether rejection of an allograft is associated with priming of cytotoxic T lymphocytes recognizing the mismatched HLA antigens of the donor. In the present study, 13 patients with good graft function and 10 with ongoing rejection of their corneal allografts were analyzed for the presence of CTL directed against mismatched donor HLA class I antigens, by limiting dilution assays. CTLs were divided into naive and primed CTLs based on the measurement of their in vitro sensitivity or resistance to anti-CD8 or cyclosporine. Cytotoxic T cell precursor frequencies directed against the mismatched donor HLA class I antigens were similar in nonrejectors and rejectors. However, rejection was strongly associated with the presence of primed, donor-specific CTL, whereas these primed cells were absent in case of good graft function. These data show that HLA antigens of a transplanted cornea are immunogenic and targets for rejection by cytotoxic T cells. Therefore, this study supports the need for HLA-A and -B matching in corneal transplantation in patients with a high probability of rejection.

Relevance of pretransplant donor-specific T cell allorepertoire for human kidney graft survival

In order to determine whether the donor-specific T cell allorepertoire evaluated in patients before transplantation can be predictive for kidney graft survival, a study has been set up in which the number and activation state of donor-specific T lymphocytes before transplantation were correlated to transplant survival time. Limiting dilution analysis assays were carried out to determine precursor frequencies of both T helper and cytotoxic T lymphocytes. The activation state of these cells was studied by evaluating the inhibitory capacity of cyclosporine on helper and cytotoxic T cells and/or a monoclonal antibody directed against CD8 on cytotoxic T cells. This study shows that neither a significant difference in the number nor activation state of donor-directed helper and cytotoxic T cells before transplantation could be detected when patients who acutely rejected their grafts were compared with patients who still had a well-functioning kidney graft after more than 10 years. Moreover, no significant differences in the donor-specific T cell repertoire were found when patients who had been subject to multiple rejection episodes were compared with patients who experienced few complications after transplantation. Therefore, we conclude that in individuals who have not been sensitized to HLA antigens of the donor, the donor-specific peripheral T cell allorepertoire prior to transplantation is not predictive of kidney graft survival.

Human leucocyte antigen phenotypes and gold-induced remissions in patients with rheumatoid arthritis

To assess possible associations between human leucocyte antigens (HLA) and the achievement of remission during gold treatment, HLA typing was performed in 67 rheumatoid arthritis (RA) patients with a gold-induced remission and in 25 control RA patients who discontinued gold therapy because of lack of efficacy. Both groups of RA patients showed a significantly higher frequency of DR4 antigen and lower frequency of DR6 than a control population. There were no significant differences in HLA antigens between remission-responders and non-responders. It is concluded that HLA typing is not helpful in predicting the therapeutic response to parenteral gold therapy.

Occurrence of allogeneic HLA and non-HLA antibodies after transfusion of prestorage filtered platelets and red blood cells: a prospective study

The incidence and consequences of HLA and non-HLA immunization were evaluated in 229 patients with aplastic thrombocytopenia. All patients were transfused with prestorage filtered red blood cells and platelets. On admission, 29 patients presented with HLA antibodies due to prior immunization by pregnancy and/or blood transfusions. Of the 200 patients showing no detectable HLA antibodies on admission, 164 could be evaluated. HLA antibodies developed in 2.7% (3 of 112) of the patients with a negative risk history of prior immunization. The occurrence of HLA antibodies in patients with a history of previous pregnancies or prior non-leukocyte-depleted blood transfusions (risk history positive) was 31% (16 of 52). Of the total of 48 patients who were or became alloimmunized, 92% (44 of 48) had a positive risk history. Ten patients with broad multispecific HLA antibodies with a panel reactivity (PRA) of greater than 70% required transfusions with HLA-matched platelets. Patients with HLA antibodies with lower PRA could be supported by random donor platelets. Two patients developed platelet-specific antibodies, causing transfusion refractoriness that necessitated selecting platelets by the absence of a platelet-specific antigen. Using prestorage leukocyte depletion of red cells and platelets with less than 5 x 10(6) residual leukocytes, 95% of the patients, including patients with a previous risk history or with HLA antibodies with low PRA, can be supported with random donor transfusions for the entire duration of their thrombocytopenic periods.

Leukocyte depletion of random single-donor platelet transfusions does not prevent secondary human leukocyte antigen-alloimmunization and refractoriness: a randomized prospective study

We studied the value of leukocyte depletion of platelet transfusions for the prevention of secondary human leukocyte antigen (HLA)-alloimmunization in patients with a high-risk of prior immunization induced by pregnancies. Seventy-five female patients with hematologic malignancies (mostly acute leukemia) and a history of pregnancy were randomized to receive either standard random single-donor platelet transfusions (mean leukocytes, 430 x 10(6) per transfusion) or leukocyte-depleted random single-donor platelet transfusions. Leukocyte depletion to less than 5 x 10(6) leukocytes per platelet transfusion (mean leukocytes, 2 x 10(6) per transfusion) was achieved by filtration. Of the 62 evaluable patients, refractoriness to random donor platelets occurred in 41% (14 of 34) of the patients in the standard group and in 29% (8 of 28) of the patients in the filtered group (P = .52); anti-HLA antibodies developed in 43% (9 of 21) of individuals in the standard group and 44% (11 of 25) of cases in the filtered group. The time toward refractoriness and development of anti-HLA antibodies was similar for both groups. We conclude that leukocyte depletion of random single-donor platelet products to less than 5 x 10(6) per transfusion does not reduce the incidence of refractoriness to random donor platelet transfusion because of boostering of anti-HLA antibodies.

The development of transplant coronary artery disease after cardiac transplantation is correlated with a predominance of CD8+ T lymphocytes in endomyocardial biopsy derived T cell cultures

Long-term survival of heart transplant recipients is limited by the development of transplant coronary artery disease (TCAD). We analysed whether the development of TCAD is correlated with the incidence of acute rejection episodes, with the formation of anti-HLA antibodies or with the composition and function of T lymphocyte cultures derived from endomyocardial biopsies. TCAD was assessed by visual analysis of annually performed coronary angiograms and defined as the presence of all vascular changes, including minor wall irregularities. One year after transplantation, 31 of the 77 patients studied had TCAD (40%). The median age and mean number of HLA mismatches in patients with or without TCAD were highly comparable. The patient groups did not differ in incidence of acute rejection episodes, nor in percentage of endomyocardial biopsies yielding T cell cultures. At 1 year after transplantation, lymphocyte cultures from 18/31 TCAD+ patients (58%) and 27/46 TCAD- patients (57%) were analysed. The TCAD+ patients had, compared with the TCAD- patients, a higher median percentage of CD8+ T cells (71% versus 25%, P = 0.06) and a lower median percentage of CD4+ T cells (4% versus 40%, P = 0.04). Similar differences were found in a longitudinal analysis of the culture results of endomyocardial biopsies (EMBs) obtained during the first year. The cytotoxic reactivity of the cultures against donor HLA class I or class II antigens was comparable in the two groups, although a difference in recognition of heart specific antigens remains possible. The fact that EMB-derived cultures from TCAD+ and TCAD- patients differed in T cell phenotype populations gives some support to the hypothesis that cellular immunological processes are involved in the development of TCAD. However, while the median values differed, the overlap of the percentages of CD8+ cells in cultures from TCAD- and TCAD+ patients shows that other factors besides CD8+ T cells also play a role.

Prevention of MHC-alloimmunization by UV-B irradiation in a murine model: effects of UV dose and number of transfused cells

The optimal dose of UV-B radiation for prevention of in vivo alloimmunization (AI) against major histocompatibility complex (MHC) antigens was investigated in a murine transfusion model. Two groups with five C57BL/6 mice (H-2b) each were transfused at weekly intervals with 1 x 10(5) or 1 x 10(6) DBA/2 (H-2d) leucocytes. Both suspensions induced anti-H-2d antibodies in all mice after the second transfusion. The minimal UV-B dose required for abolition of alloreactivity in the mixed leucocyte reaction (MLR) was 0.6 J/cm2. This dose completely prevented the onset of MHC-AI in all five mice transfused with six suspensions containing 1 x 10(5) leucocytes. In contrast, suspensions with 1 x 10(6) leucocytes and exposed to 0.6 J/cm2 induced immunization in 4/5 mice. Further increase of the dose to 1.8 or 5.4 J/cm2 did not prevent the onset of MHC-AI. The use of UV radiation for prevention of secondary MHC-AI was investigated in five mice with a primed immune system. Transfusion of suspensions with 1 x 10(5) leucocytes and irradiated at a dose of 1.8 J/cm2 did not prevent booster reactions. We conclude that the number of leucocytes per transfusion determines the efficacy of UV irradiation for the prevention of MHC-AI. For UV irradiation of human platelet concentrates (PCs) we propose to reduce the number of leucocytes by centrifugation prior to UV exposure. UV-B irradiation of PCs with high numbers of leucocytes may not be effective for prevention of alloimmunization.

IgG antibodies against an HLA antigen are associated with activated cytotoxic T cells against this antigen, IgM are not

Pre-existing alloantibodies against the mismatched HLA-A and HLA-B antigens of the donor, when present in current sera, are believed to be detrimental to kidney graft survival. When these antibodies are present only in historical sera, their immunoglobulin class has reported to be important with respect to the expected graft survival, IgG antibodies being associated with poor graft prognosis and IgM with reasonable graft survival. In the present study, we have tested whether the immunoglobulin class of anti-HLA antibodies is reflected in the activation state of CTLs directed against these HLA antigens as measured by their in vitro resistance or sensitivity to CsA. The results indicate that the presence of IgG anti-HLA antibodies is associated with the presence of activated CTLs (CsA resistant), whereas in the case of IgM antibodies, mainly naive CTLs (CsA sensitive) are found. This observation may explain the different prognoses of historical positive crossmatches due to IgG versus IgM alloantibodies.

High-affinity cytotoxic T lymphocytes after non-HLA-sharing blood transfusion--the other side of the coin

Previously, we have shown that pretransplantation blood transfusion modulates the T cell repertoire to a great extent. Patients receiving a BT from a donor sharing one HLA haplotype with the patient (HLA-sharing BT) develop CTL nonresponsiveness against cells of the BT donor and show a selective decrease in the usage of T cell receptor V beta families. The present study has focused on the analysis of the T cell repertoire in patients receiving an HLA mismatched (non-HLA-sharing) BT. CTL precursor frequencies were measured against single class I-mismatched antigens in split-well analysis. In addition, blocking studies of CTL-target cell interaction were performed with anti-CD8 monoclonal antibodies. The results demonstrate that non-HLA-sharing BT immunizes and induces the generation of CD8 independent, high-affinity CTL against immunogenic class I-mismatched antigens. Such HLA class I antigens might become nonacceptable mismatches in subsequent organ transplantation.

Functional and molecular characterization of graft-infiltrating T lymphocytes propagated from different biopsies derived from one heart transplant patient

Alloreactive T lymphocytes play an important role in graft rejection. In the present study, we have analyzed the cytolytic capacity against donor cells of graft infiltrating T lymphocyte cell lines, which were propagated from various endomyocardial biopsies taken at different time points after transplantation, including during a rejection crisis. Also, T cell clones were generated from the rejection biopsy and evaluated for their cytolytic capacity and nucleotide composition of the TCR alpha and beta chains. The results of these studies revealed a strong cytolytic activity against donor cells by T cells derived from the rejection biopsy, whereas from the other biopsies, no cytolytic T cell clones could be established. The T cells that were responsible for this activity, as detected by T cell cloning and TCR gene analysis, could not been identified in earlier biopsies, indicating that these cytolytic cells were recently recruited toward the endomyocardium.

Differential avidity and cyclosporine sensitivity of committed donor-specific graft-infiltrating cytotoxic T cells and their precursors. Relevance for clinical cardiac graft rejection

We have used limiting dilution analysis to study the qualitative and quantitative differences between graft-infiltrating cytotoxic T cell populations propagated from endomyocardial biopsies of heart transplant patients who experienced one or more acute rejection episodes and patients who never showed signs of rejection. Limiting dilution cultures were stimulated with autologous or donor cells both in the absence or in presence of cyclosporine and of CD8 in the cytotoxic phase. Almost all antigen-primed, committed cytotoxic T cells (cCTL) present in the graft of patients with rejections were CsA resistant. In contrast, in most patients of the nonrejector group, a substantial part of the cCTL could be inhibited by CsA. The CTL precursors (pCTL) in both groups were predominantly CsA sensitive. Addition of CD8 mAb during the cytotoxicity phase of the limiting dilution analysis was used to differentiate between CTL populations with high avidity for donor antigens and populations with low avidity. The predominant subpopulation in the graft of rejectors was a CsA-resistant cCTL with high avidity, while in the graft of most nonrejectors, cCTL with low avidity dominated. In most rejectors, CD8 mAb had only a minor influence on the pCTL frequency estimates, and thus on T cells with high avidity. CsA-sensitive pCTL with high avidity might represent an intermediate stage between the naive pCTL and mature, functional, CsA-insensitive cCTL with high avidity for donor antigens.

Characteristics of graft-infiltrating lymphocytes after human heart transplantation. HLA mismatches and the cellular immune response within the transplanted heart

The influence of HLA mismatches between donor and recipient on the phenotypes, function, and specificity of T-lymphocyte cultures derived from endomyocardial biopsies was studied in 118 heart transplant recipients. In case of HLA-DR mismatches, the majority of the EMB-derived cultures were dominated by CD4+ T cells while, in patients with HLA-A and -B mismatches but without DR mismatches, CD8+ T cells comprised the predominant T-cell subset. Cytotoxicity against donor antigens was observed in 75% of the cultures. A significantly (p < 0.005) lower proportion of the cultures showed cytotoxicity against HLA-A antigens (36%) when compared with HLA-B (53%) or HLA-DR (49%). An HLA-A2 mismatch elicited a cytotoxic response that was comparable to that found against HLA-B and -DR antigens: 62% of the cultures from HLA-A2 mismatched donor-recipient combinations was reactive against A2. A higher number of A, B, or DR mismatches resulted in a higher number of cytotoxic cultures directed against these antigens. A higher number of HLA-B and -DR mismatches was associated with a lower freedom from rejection. Our data indicate that, despite the use of adequate immunosuppressive therapy, the degree of HLA matching plays a crucial role in the immune response against a transplanted heart, resulting in a significant effect on freedom from rejection.