Unsensitized Recipients Research Articles

Endogenous memory T cells with donor-reactivity: early post-transplant mediators of acute graft injury in unsensitized recipients.

The pretransplant presence of endogenous donor-reactive memory T cells is an established risk factor for acute rejection and poorer transplant outcomes. A major source of these memory T cells in unsensitized recipients is heterologously generated memory T cells expressing reactivity to donor allogeneic MHC molecules. Multiple clinical studies have shown that the pretransplant presence of high numbers of circulating endogenous donor-reactive memory T cells correlates with higher incidence of acute rejection and decreased graft function during the first-year post-transplant. These findings have spurred investigation in preclinical models to better understand mechanisms underlying endogenous donor-reactive memory T-cell-mediated allograft injury in unsensitized graft recipients. These studies have led to the identification of unique mechanisms underlying the activation of these memory T cells within allografts at early times after transplant. In particular, optimal activation to mediate acute allograft injury is dependent on the intensity of ischaemia-reperfusion injury. Therapeutic strategies directed at the recruitment and activation of endogenous donor-reactive memory T cells are effective in attenuating acute injury in allografts experiencing increased ischaemia-reperfusion injury in preclinical models and should be translatable to clinical transplantation.

Pancreas.

Even though pancreas transplant numbers have steadily declined over the past decade, new listings increased in 2014 compared with the previous year, notably for pancreas transplant alone (PTA) and simultaneous pancreas-kidney transplant. The number of new PTAs also increased over the past two years. Whether this is a sustainable trend remains to be seen. Significant events in 2014 included implementation of a new pancreas allocation system and development of a proposed uniform definition of pancreas graft failure. Meanwhile, overall pancreas transplant rates and outcomes continued to improve. Substantial decline in pancreas after kidney transplants remains a serious concern. SRTR has not published pancreas graft failure data in the program-specific reports for the past two years. While this will not change in the near future, the acceptance of a uniform definition of graft failure is a crucial first step toward resuming graft failure reporting. Continued improvements and innovation, both surgical and immunological, will be critical to keep pancreas transplant as a viable option for treatment of insulin-dependent diabetes. As alternative therapies for diabetes such as islet transplant and artificial pancreas are evolving, improved outcomes with minimizations of complications are more important than ever.

Survival in Sensitized Lung Transplant Recipients With Perioperative Desensitization

Donor-specific HLA antibodies (DSA) have an adverse effect on short-term and long-term lung transplant outcomes. We implemented a perioperative strategy to treat DSA-positive recipients, leading to equivalent rejection and graft survival outcomes. Pretransplant DSA were identified to HLA-A, B, C, DR and DQ antigens. DSA-positive patients were transplanted if panel reactive antibody (PRA) ≥30% or medically urgent and desensitized with perioperative plasma exchange, intravenous immune globulin, antithymocyte globulin (ATG), and mycophenolic acid (MPA). PRA-positive/DSA-negative recipients received MPA. Unsensitized patients received routine cyclosporine, azathioprine and prednisone without ATG. From 2008-2011, 340 lung-only first transplants were performed: 53 DSA-positive, 93 PRA-positive/DSA-negative and 194 unsensitized. Thirty-day survival was 96 %/99%/96% in the three groups, respectively. One-year graft survival was 89%/88%/86% (p = 0.47). DSA-positive and PRA-positive/DSA-negative patients were less likely to experience any ≥ grade 2 acute rejection (9% and 9% vs. 18% unsensitized p = 0.04). Maximum predicted forced expiratory volume (1 s) (81%/74%/76%, p = NS) and predicted forced vital capacity (81%/77%/78%, respectively, p = NS) were equivalent between groups. With the application of this perioperative treatment protocol, lung transplantation can be safely performed in DSA/PRA-positive patients, with similar outcomes to unsensitized recipients.

Posttransplant soluble B-cell activating factor kinetics in pediatric recipients of first kidney allograft.

Development of de novo donor-specific antibodies (dnDSA) is associated with late or chronic antibody-mediated rejection (CAMR) and poor graft outcome in low-risk kidney transplant recipients. High-level soluble B-cell activating factor (sBAFF) was observed in kidney recipients at higher risk of developing dnDSA. We longitudinally analyzed sBAFF levels in 81 consecutive primary pediatric kidney recipients monitored for de novo human leukocyte antigen (HLA) antibody (Ab) occurrence to gain insight into the events conditioning B-cell activation posttransplant and to analyze the usefulness of paired DSA-sBAFF monitoring in this clinical setting. At a median follow-up of 65 months, 23 patients (28%) developed dnDSA, with 13 of 23 developing CAMR. Irrespective of HLA Ab status, sBAFF levels progressively increased in all patients in the first posttransplant year, thereafter reaching a plateau. sBAFF levels were influenced by the degree of HLA class I antigen match and donor age. Despite higher levels of sBAFF in HLA Ab-positive patients (median and 95% confidence interval sBAFF in DSA+non-DSA patients: 568, 534-608 pg/mL vs. 502, 422-548 pg/mL in Ab-negative patients; P<0.05), we found that sBAFF monitoring could not predict DSA development by a time to event longitudinal analysis. Moreover, sBAFF kinetics up to CAMR onset could not anticipate CAMR development in the DSA cohort. Our findings provide evidence of early posttransplant B-cell activation even in unsensitized recipients of first kidney allograft. The significance of this activation, likely induced by exposition to the allograft, is yet unclear.

Improved Survival with Perioperative Desensitization in Lung Transplant Patients with Donor Specific Antibodies (DSA)

Purpose HLA antibodies and DSA are historically associated with decreased lung allograft survival and rejection, and are a barrier to lung transplant. Few results of interventions have been reported. We report the success of a perioperative desensitization protocol for sensitized lung recipients. Methods and Materials Recipients were tested for DSA at HLA A, B, C, DR and DQ. DSA+ patients were transplanted if PRA≥30% or high medical urgency and were desensitized with perioperative plasma exchange, intravenous immune globulin, antithymocyte globulin, and MMF instead of standard azathioprine(aza). Recipients with positive panel reactive antibodies (PRA+) but no DSA (DSA-) received MMF instead of aza. Routine therapy for unsensitized (PRA0) patients was cyclosporine, aza and prednisone without ATG. Results 340 first lung transplants were performed 2008-11: 53 DSA+, 93 PRA+DSA-,194 PRA0. Age, diagnosis, CMV status, single vs double lung, and donor characteristics (age, smoking, PaO 2 , donation after cardiac death, EVLP) were similar between groups. By Ab group (DSA+ / PRA+DSA- / PRA0): Median wait time to transplant was 167/92/100d (p=0.02). More DSA+ were female (62/44/36% p=0.003), and were urgent status at transplant (85/80/67% p=0.0005) with higher mean LAS (42/39/36 p=0.02). Despite increased pre-transplant morbidity, sensitized patients were less likely to experience any ≥ grade 2 acute rejection (9/9/18% p=0.04); max %predFEV1(81/74/76), %predFVC (81/77/79) and graft survival were equivalent between groups. [figure 1] Conclusions With this desensitization protocol, lung transplant can be safely performed in highly sensitized recipients with similar outcomes to unsensitized recipients.

Short history about renal transplantation program in Iran and the world: Special focus on world kidney day

World kidney day on 8 March 2012 provides a chance to reflect on the success of kidney transplantation as a therapy for end-stage renal disease (ESRD) that surpasses dialysis treatments for the quality and quantity of life and for cost effectiveness. An experimental, risky, and very limited treatment option 50 years ago is now routine clinical practice in more than 80 countries. What was limited to a few people in a small number of academic centers is now routinely transforming lives in most high- and medium-income countries. The first successful organ transplantation occurred between identical twins in Boston on 23 December 1954. Between 1965 and 1980, patient survival progressively improved to 90%, and graft survival rose to at least 60%. Thirty years on, unsensitized recipients of first deceased- or living-donor kidney transplants can expect 1-year patient survival of 95% and transplant survival of at least 90%. Recent developments have also led to excellent results from ABO blood group-incompatible transplants in recipients with low-titer ABO antibodies (1).

Sensitized Recipients Exhibit Accelerated but not Hyperacute Rejection of Vascularized Composite Tissue Allografts

Currently, the donor-recipient matching process for vascularized composite tissue allotransplantation (VCTA) closely follows the standard practices for solid organ transplantation. Sensitization is considered a contraindication to VCTA. However, the role of sensitization in VCTA rejection is largely unstudied. Major histocompatibility-mismatched ACI (RT1) donors and Wistar Furth (WF) (RT1) recipients were used to determine whether sensitization would lead to hyperacute rejection in VCTA as in other organs, such as kidneys. WF rats were presensitized to ACI antigens by skin transplantation and received heterotopic osteomyocutaneous VCTA flaps. Kidney transplants served as controls. Production of anti-donor antibody was detected in WF recipients after rejection of the ACI skin grafts. Sensitized WF rats rejected VCTA grafts from ACI rats significantly faster (P<0.05) than unsensitized recipients, but not hyperacutely. Rejection in the sensitized recipients was not prevented by immunosuppression with FK506 and mycophenolate mofetil. In contrast, kidney allografts from ACI rats were hyperacutely rejected within 30 min by sensitized recipients. To confirm the role of antibody-mediated rejection in the sensitized recipients, serum from presensitized rats was adoptively transferred into naïve WF rats. Hyperacute rejection occurred only in transplanted kidneys but not VCTA. Histologic examination of tissues from acceleratedly rejected VCTA showed dense lymphocytic infiltrates, and no antibody deposition. VCTA are rejected in an accelerated fashion but not hyperacutely in the presence of allosensitization and preformed anti-donor antibody. The rejection of VCTA in sensitized recipients is mainly cell mediated and differs mechanistically from that for renal transplants.

Impact of human leukocyte antigen matching and recipients’ panel reactive antibodies on two-year outcome in presensitized renal allograft recipients

Background Renal transplantation in sensitized candidates remains a highly significant challenge worldwide. The production of panel reactive antibody (PRA) against human leukocyte antigen (HLA) is a major risk factor in presensitized recipients. The aim of this study was to evaluate the impact of HLA matching and recipients’ PRA on two-year outcome in presensitized renal allograft recipients. Methods We determined the percentage of panel reactivity and specificity of anti-HLA immunoglobulin (Ig) G antibodies in 73 presensitized renal allograft recipients compared with 81 unsensitized recipients (control group). HLA genotyping of both recipients and corresponding donors was performed by PCR with sequence-specific primers (PCR-SSP). We analyzed the factors influencing the early graft outcome (two-year rejection rates and survival rates of the grafts), including HLA mismatching, class and degree of panel reactivity, and target antigen of donors. Results Presensitized recipients had a worse two-year outcome than unsensitized recipients (P=0.019 for rejection rate, P=0.01 for survival rate). The difference in number of HLA-mismatched alleles with either 6-antigen matching (Ag M) standard or amino acid residue matching (Res M) standard was not significant between the rejection and non-rejection groups of presensitized recipients or between the graft survival group and graft loss group. Compared with the control group, recipients with both PRA-I and PRA-II antibodies had a significantly worse two-year outcome (P=0.001 for rejection rate, P=0.002 for survival rate). The two-year outcomes of the peak PRA &gt;50% group and its subgroup, at-transplant PRA &gt;50% group, were significantly worse compared with the control group (P=0.025 and P=0.001 for rejection rate, P=0.043 and P=0.024 for survival rate). The rejection rates of the at-transplant target antigen positive group and its subgroup, HLA-I target antigen positive group, were significantly higher than the control group (P=0.001 and P=0.001), target antigen negative group (P=0.003 and P=0.001), and peak target antigen positive with negative at-transplant target antigen group (P=0.024 and P=0.002). Two-year graft survival rates of the target antigen positive group and HLA-I target antigen positive group were significantly lower than the control group (P=0.012 and P=0.001). The two-year outcome of target antigen unknown group was similar to that of the target antigen positive group. Presensitized recipients with pre-transplant plasmapheresis or immunoadsorption (PRA prepared group) had a better but non-significant two-year outcome than the control group. However, the PRA unprepared presensitized recipients were different to the control group (P=0.004 for rejection rate and P=0.005 for survival rate). Hyperacute rejection (HR) occurred in three recipients with positive HLA-I target antigen and without mismatch according to Res M and in one case with positive PRA-II (for an unknown target antigen). No HR occurred in eight cases with positive HLA-II target antigens. Conclusions Pre-transplant PRA preparations might improve the access of presensitized patients to renal donors. Avoiding antigen-positive donors remains a fundamental measure in preventing HR and early rejections. Chin Med J 2009;122(4):420–426

The evolving notion of “senior” kidney transplant recipients

The maximum age of recipients expected to benefit with a kidney transplant has increased in the past three decades. In 1980, patients older than age 50 were not listed for a transplant. In 2004, almost 90% aged 50-60 yr with end-stage renal disease were listed, and some were even older than age 80. We summarize previous articles to illustrate how the notion of "senior" has evolved for kidney transplantation, and using data reported to the Organ Procurement Transplant Network, describe characteristics, treatments and outcomes in recipients older than 50 yr. Fractions of male, white, non-obese, unsensitized recipients and use of expanded criteria donors increased in cohorts with increasing recipient age. The percentage of recipients with hypertension or diabetes decreased, but the percentage with cancer increased. The fraction spared steroids increased with increasing age, but other aspects of immunosuppression were not remarkably different. No differences in early outcomes were notable, and elderly recipients likely did not return to dialysis. However, both graft and patient survival rates decreased with increasing age. Although a small fraction was selected, and survival rates were lower, patients older than 80 yr received kidney transplants.

C4d Deposition and Clearance in Cardiac Transplants Correlates With Alloantibody Levels and Rejection in Rats

Antibody-mediated rejection of human cardiac transplants is correlated with C4d deposits and macrophage infiltrates in capillaries of endomyocardial biopsies. We produced an antibody to rat C4d to study C4d deposition and clearance in Lewis rats that were sensitized with a blood transfusion from DA rats 7, 14 or 21 days before cardiac transplantation. Cyclosporin A (CsA) immunosuppression was initiated after transplantation at a dose that inhibited graft rejection, antibody production and C4d deposition in unsensitized recipients. Blood transfusion elicited high levels of circulating IgG alloantibodies, predominantly of the complement-activating IgG2b subclass, that peaked 14 days after transplantation. At this time, macrophages accumulated in capillaries, and C4d deposits were diffuse and intense on arteries, capillaries and veins. Grafts that survived 90 days in sensitized recipients still had deposits of C4d that were associated with increased interstitial fibrosis and vasculopathy in arteries. Clearance of C4d was determined by retransplanting DA cardiac allografts from Lewis recipients back to DA recipients. C4d deposits were decreased to minimal levels within 5 days after retransplantation. Thus, C4d deposition is not limited to the capillaries, but extends throughout the arterial tree, and despite formation of a covalent bond, C4d is cleared within days.

Particle-induced circulatory disturbances in transplanted rhesus macaque kidneys

Abstract We have demonstrated the presence of crystalline particles in University of Wisconsin (UW) solution used to perfuse rhesus monkey kidney transplants. These particles were visible in obstructed blood vessels and associated with immediate graft thrombosis and necrosis. This occurred in 25.7% of kidneys perfused with UW solution and transplanted into young, unsensitized recipients. Two molecular species of crystals were defined by mass spectrometry. The particle size ranged from 3 to greater than 100 μm, with a preponderance of particles less than 25 μm in diameter. Such particles are not removed by 40-μm filtration, but can be removed by centrifugation. With extensive use of UW solution for organ storage, the potential for particle-induced damage in small vessels in both experimental and human transplants needs to be carefully scrutinized.

Particle-induced circulatory disturbances in transplanted rhesus macaque kidneys

We have demonstrated the presence of crystalline particles in University of Wisconsin (UW) solution used to perfuse rhesus monkey kidney transplants. These particles were visible in obstructed blood vessels and associated with immediate graft thrombosis and necrosis. This occurred in 25.7% of kidneys perfused with UW solution and transplanted into young, unsensitized recipients. Two molecular species of crystals were defined by mass spectrometry. The particle size ranged from 3 to greater than 100 microm, with a preponderance of particles less than 25 microm in diameter. Such particles are not removed by 40-microm filtration, but can be removed by centrifugation. With extensive use of UW solution for organ storage, the potential for particle-induced damage in small vessels in both experimental and human transplants needs to be carefully scrutinized.

Positive remote crossmatch: impact on short-term and long-term outcome in cadaver renal transplantation.

A positive crossmatch with a "current" recipient serum (drawn shortly before the proposed transplant) is a contraindication to renal transplantation because of the risk of hyperacute rejection. Conflicting data have been reported concerning the significance of a positive crossmatch with "remote" sera (obtained months or years earlier) when the current crossmatch is negative. Recipients of a first or second cadaver transplant between June 1988 and April 1994 were studied. All transplants were performed with a negative "current" crossmatch. Retrospective crossmatches using "remote" sera were performed for all sensitized recipients. Recipients with a positive remote crossmatch (RXM) demonstrated a higher incidence of delayed graft function and of acute rejection and graft loss occurring in the first year posttransplant than did sensitized recipients with a negative RXM or unsensitized recipients. In multivariate analysis, only recipients with both a positive RXM and delayed graft function were at significantly higher risk for graft loss. Grafts surviving the first year demonstrated similar half-lives whether the RXM was positive or negative. The positive RXM, possibly in conjunction with other factors leading to very early graft damage, is a significant predictor of unfavorable transplant outcome in first and second renal transplants. This effect is seen early in the transplant course, and there seems to be no impact on outcome after the first year. Newer immunosuppressive modalities may help to reduce the early negative impact.

Development of an antibody specific to major histocompatibility antigens detectable by flow cytometry after lung transplant is associated with bronchiolitis obliterans syndrome.

Chronic allograft rejection manifested as bronchiolitis obliterans syndrome (BOS) is the leading cause of late death after lung transplantation. Although increasing evidence suggests an association between anti-human leukocyte antigens (HLA) antibodies and chronic rejection of kidney or heart allografts, the clinical significance of anti-HLA antibodies in lung recipients is less clear, especially in previously unsensitized recipients. The use of flow cytometry based panel reactive antibody (flow-PRA) provides a highly sensitive means to identify the development of de novo anti-HLA antibodies in lung recipients. Flow-PRA testing was used to analyze the pre- and posttransplant sera in stable BOS free lung recipients who survived at least 6 months. Patients without prior sensitization as defined by a negative pretransplant flow-PRA were analyzed posttransplant for the presence of anti-HLA antibodies by flow-PRA. A proportional hazards model was used to determine the impact of anti-HLA antibody on BOS risk. Sera from 90 recipients at Duke University with negative pretransplant flow-PRA were tested by flow-PRA at various time points after transplant. Sera from 11% (10/90) of recipients were found to contain anti-HLA antibodies detectable by flow-PRA. Nine patients (90%) developed anti-HLA antibodies specific for donor antigens, and one patient developed anti-HLA class II antibodies, not specific to donor antigens. Among the nine patients with donor antigen specific antibodies, flow-PRA specificity analysis demonstrated eight were specific for class II antigens and one for class I antigens. In a multivariate model that controls for other BOS risk factors, a positive posttransplant flow-PRA was significantly associated with BOS grades 1,2, or 3 (hazard ratios [HR] 3.19; 95% confidence interval [CI]: 1.41-7.12, P=0.005) and BOS grade 2 or 3 (HR 4.08; 95% CI: 1.66-10.04, P=0.002). Four patients with de novo anti-HLA antibodies died during follow-up; all four had BOS. Among BOS patients, the presence of anti-HLA antibodies was associated with a significantly worse survival (P =0.05, log-rank test). Although uncommon, previously unsensitized lung transplant recipients can develop anti-HLA antibodies to donor class II antigens. The development of de novo anti-HLA antibodies significantly increases the risk for BOS, independent of other posttransplant events. Furthermore, de novo anti-HLA antibodies identify BOS patients with significantly worse survival. Additional studies are needed to determine if class II-directed anti-HLA antibodies contribute mechanistically to the chronic rejection process in lung recipients.

Cold ischemia time: an independent predictor of increased HLA class I antibody production after rejection of a primary cadaveric renal allograft.

Cadaveric kidneys experiencing longer cold ischemia time (CIT) are associated with higher levels of delayed graft function, acute rejection, and early graft loss. One mechanism to explain these results is that ischemia/reperfusion (I/R) injury makes the allograft more immunogenic by upregulating molecules involved in the immune response (e.g., HLA Class I/II). We evaluated the influence of CIT on the production of HLA Class I antibody level, measured by an antihuman globulin panel reactive antibody (AHG PRA) level, in 90 unsensitized recipients of primary cadaveric renal transplants (from a total of 1442 between 1985 and 1997) who rejected their kidneys. By multivariate analysis, a CIT of 15 hr or more (vs. < 15 hr) independently increased the risk of the AHG Class I PRA level being > or = 20% after unsensitized patients rejected their first kidneys (relative risk=3.57; 95% confidence interval=1.26 to 10.14; P=0.01), despite the same degree of Class I/II mismatch between the two CIT groups. The overall mean peak PRA level after primary kidney rejection was significantly lower for the CIT < 15 hr group (25.9%+/-33.9; n=24) compared with the CIT > or = 15 hr group (46.3%+/-36.5; n=66) (P<0.001). Longer CIT induces a humorally more immunogenic kidney.

Effect of alpha4-integrin blockade on CD4+ cell-driven late airway responses in the rat.

The blockade of alpha4 integrins with a monoclonal antibody (TA-2) decreases late airway responses (LR) in ovalbumin (OVA)-sensitized and challenged rats. In this study, we used a model of CD4+ cell-driven LR to test the hypothesis that alpha4-integrin blockade involves interference with T-cell activation in the inhibition of LR. Purified CD4+ cells from OVA-sensitized rats were transferred to unsensitized recipients, which received either TA-2 or a control antibody (cAb), and were OVA-challenged. A sham-challenged group was also studied. LR, calculated from pulmonary resistance after challenge, were reduced in the TA-2 group compared with the cAb group (p = 0.015). Total cell counts, macrophages, neutrophils, and lymphocytes in bronchoalveolar lavage (BAL), and CD3+ cells in airway sections, were unaffected. The cAb group had higher numbers of cells expressing interleukin-5 (IL-5) mRNA (55.2 +/- 3.39 cells/1,000, mean +/- SEM) and major basic protein (MBP) (6.2 +/- 0.4/100 cells) in bronchoalveolar lavage (BAL), than the TA-2 group (25.37 +/- 2.41 IL-5+ and 2.7 +/- 0.2 MBP+) and the sham group (12.37 +/- 0.96 IL-5+, 1.7 +/- 0.1 MBP+). Interferon gamma (IFN-gamma) mRNA+ cells were downregulated in both OVA-challenged groups, compared with the sham group. Our results suggest that the attenuation of LR and eosinophilia by alpha4-integrin blockade may involve interference with CD4+ cell activation and IL-5 expression.

Immunobiology of xenogeneic cornea grafts in mouse eyes. II. Immunogenicity of xenogeneic cornea tissue grafts implanted in anterior chamber of mouse eyes.

Xenogeneic corneal fragments (guinea pig) are highly resistant to immune rejection in the anterior chamber of mouse eyes. Because guinea pigs and mice are discordant (i.e., mouse serum normally contains guinea pig reactive xenoantibodies), we wished to determine the extent to which xenogeneic corneal fragments placed intraocularly in normal and specifically sensitized mice activated xenoreactive T and B cells. Guinea pig corneas, deprived surgically of epithelium, were cut into fragments and inserted into the anterior chamber of eyes of BALB/c mice, adjacent to the central cornea of the recipient. Antibody (immunoglobulin [Ig]M, IgG) and delayed type hypersensitivity (DTH) immune responses of recipient mice to guinea pig xenoantigens were assessed. The fate of xenogeneic cornea implants was assessed in mice immunized systemically to guinea pig antigens. Guinea pig spleen cells and corneal fragments implanted s.c. induced within 2 weeks of immunization both DTH and IgG antibodies to guinea pig xenoantigens. By contrast, xenogeneic corneal fragments implanted in the anterior chamber of mouse eyes evoked no change in recipient humoral immune status and induced mild guinea pig-specific DTH only after 5 weeks. Presensitization of mice to guinea pig xenoantigens failed to increase the proportion of grafts that were regarded as rejected, but the onset of rejection in failed grafts occurred earlier than in unsensitized recipients. Active systemic immunization of mice bearing intracameral guinea pig corneal fragments failed to curtail the grafts' survival. Guinea pig corneal fragments implanted in the anterior chamber of normal mice failed to induce anterior chamber-associated immune deviation. Xenogeneic corneal fragments implanted in the anterior chamber of eyes of normal mice display strikingly reduced immunogenicity, and an inability to induce anterior chamber-associated immune deviation. These properties are discussed in terms of the vulnerability of guinea pig corneal tissue to immune rejection within the eye.

INCREASED RISK OF ACUTE AND CHRONIC REJECTION IN SENSITIZED KIDNEY RECIPIENTS WITH HLA CLASS II-DIRECTED DONOR ANTIGEN-SPECIFIC ANTIBODIES.

684 Kidney recipients with preformed anti-HLA antibodies (Abs) have more acute rejection episodes (AR), a higher incidence of chronic rejection (CR), and a lower graft survival rate than unsensitized recipients, even with negative pretransplant crossmatch with donor cells. Recent reports indicate that acute rejection and graft loss correlate more closely with the presence of antibodies detected pretransplant by the ELISA technique than by cytotxicity techniques. However, until recently, the independent detection of HLA class I- vs. class II-directed antibodies was not possible. We utilized a highly sensitive ELISA technique with purified class I or class II antigens allowing for the independent identification of class I- vs. class II-directed Abs (One Lambda, Canoga Park, CA) to determine whether the presence of class II-directed antibodies in addition to class-I-directed antibodies correlated with an increased incidence of AR or CR. We tested sera from 40 kidney recipients who had class I panel reactive Ab > 10% (determined by antiglobulin cytotoxicity technique) at the time of transplant. We determined the frequency of recipients who also had class II-directed antibodies and the incidence of AR and CR. Of these 40 recipients, 25 (63%) also had class II-directed Abs. We observed that 52% (13/25) of recipients with and 53% (8/15) of recipients without class II-directed antibodies experienced AR; thus, the mere presence of class II-directed Abs did not correlate with a higher AR rate. However, this ELISA technique identified 7 recipients with donor class II antigen-specific antibodies; only 1 recipient had a positive B cell cytotoxic crossmatch at the time of transplant. All 7 of these recipients experienced at least 1 AR episode and, to date, 3 have developed CR. Two recipients were shown to have donor class I antigen-specific antibodies detected by ELISA but not by cytotoxic techniques. One had AR, the other did not. None of the recipients with class I only directed antibodies has developed CR. These results suggest that this ELISA technique identifies recipients with class I-directed antibodies who also have class II donor antigen-specific antibodies and are at the highest risk for AR and CR. The availability of this information pretransplant may allow for individualization and optimization of immunosuppression.

Increased rejection of murine allogeneic bone marrow in presensitized recipients.

The role of presensitizing murine recipients with donor spleen cells prior to T cell-depleted or -repleted H-2 compatible allogeneic bone marrow transplantation (BMT) was investigated at two different doses of total body irradiation (TBI). Recipients that were presensitized with 2 x 10(7) irradiated donor spleen cells at 1 week before a sublethal dose of 6 Gy TBI and BMT showed no evidence of donor blood chimerism while unsensitized recipients showed about 80% donor engraftment as determined by blood Gpi phenotyping. After raising the TBI dose to 9.5 Gy an increase in mortality from marrow failure was observed in presensitized animals. No significant engraftment-promoting effect of up to 2 x 10(6) T cells (20% of total marrow dose) was seen either in presensitized or unsensitized mice. It can be concluded that presensitized recipients are more susceptible to acute marrow rejection and that T cells added to the bone marrow did not influence the level of donor engraftment in these recipients.

ANTI-CD45 MONOCLONAL ANTIBODY PERFUSION OF HUMAN RENAL ALLOGRAFTS PRIOR TO TRANSPLANTATION A SAFETY AND IMMUNOHISTOLOGICAL STUDY

The perfusion of kidneys with anti-CD45 monoclonal antibodies prior to transplantation offers a means of targeting passenger antigen-presenting cells with the aim of reducing the subsequent incidence of rejection episodes. A safety study was performed in humans of such pretreatment in 40 unsensitized recipients of first cadaveric renal grafts, who were followed for 3 months after transplantation. A 50-ml solution containing 2 mg of each of the rat anti-CD45 mAbs YTH 24.5 and YTH 54.12 was injected into the allograft renal artery ex vivo and just before transplantation while the renal vein was kept clamped. No patients died, but 4 grafts were lost. Two were lost due to primary nonfunction, 1 was lost because of late renal artery thrombosis, and 1 was lost to rejection. There were no cases of renal vein thrombosis and 1 trivial renal artery stenosis, and only 2 patients produced human anti-rat antibodies. Between 63.5% and 100% (median 96.4%) of CD45+ cells in the postperfusion biopsies were coated with anti-CD45 as determined by double-immunolabeling. The number of patients experiencing rejection episodes was inversely associated with this "antibody uptake": 75% of the low uptake group (< 95%) had at least 1 rejection episode, compared with 22% of the high uptake group (> or = 95%) (P = 0.001). The complement components C3 and C5b-9 colocalized with perfused anti-CD45 in 32/33 (97.0%) and 11/33 (33.3%) of the biopsy specimens, respectively. We conclude that: (1) this technique appears free of adverse effects, (2) high antibody uptake within the kidney is associated with a lower incidence of rejection, and (3) the antibodies used fix and activate complement in vivo.