Isabelle G. Wood

Investigations into the role of anti-HLA class II antibodies in TRALI.

BACKGROUND : TRALI is thought to be triggered by recipient‐specific anti‐HLA class I or antibodies against neutrophils in donor plasma. Recently, anti‐HLA class II have also been implicated. The prevalence of anti‐HLA class II was investigated in normal volunteer platelet donors and in two nonfatal TRALI cases utilizing a flow‐based assay. Potential target antigens also were investigated.

Impact of Pretransplant Anti-HLA Antibodies on Outcomes in Lung Transplant Candidates

RATIONALE The prevalence of anti-HLA antibodies in lung transplant candidates and their impact on waitlist and transplant outcomes is not known. OBJECTIVES We examined the prevalence of pretransplant anti-HLA antibodies at varying thresholds and evaluated their impact on outcomes before and after lung transplantation. METHODS We performed a single-center retrospective cohort study including all patients listed for lung transplantation between January 2008 and August 2012. Per protocol, transplant candidates were assessed by solid phase LABscreen mixed Class I and II and LABscreen Single Antigen assays. MEASUREMENTS AND MAIN RESULTS Among 224 patients, 34% had anti-HLA antibodies at mean fluorescent intensity (MFI) greater than or equal to 3,000 (group III), and 24% had antibodies at MFI 1,000 to 3,000 (group II). Ninety percent of the patients with pretransplant anti-HLA antibodies had class I antibodies, whereas only seven patients developed class II alone. Patients in group III were less likely to receive transplants than patients without any anti-HLA antibodies (group I) (45.5 vs. 67.7%, P = 0.005). Wait time to transplant was longer in group III than group I, although this difference did not meet statistical significance, and waitlist mortality was similar. Among transplant recipients, antibody-mediated rejection (AMR) was more frequent in group III than in group II (20% vs. 0%, P = 0.01) or group I (6.3%, P = 0.05). CONCLUSIONS The presence of anti-HLA antibodies at the high MFI threshold (>3,000) was associated with lower transplant rate and higher rates of AMR. Screening for anti-HLA antibodies using the 3,000 MFI threshold may be important in managing transplant candidates and recipients.

Differential IL-2 receptor expression in renal allograft recipients treated with an anti-IL-2-receptor antibody.

Patients were entered into a randomized trial of prophylaxis for renal allograft rejection by the administration of an anti-human IL-2 receptor antibody, anti-Tac, during the first ten days posttransplant. Interleukin-2 receptor (IL-2 R) expression was measured using two anti-IL-2 R monoclonal antibodies (moAbs), anti-Tac and 1HT4-4H3. These two antibodies recognize closely spaced epitopes on the 55 kD chain of the IL-2 R. IL-2 R expression was examined on peripheral blood small lymphocytes in three groups of patients who received: (A) cyclosporine CsA and prednisone for baseline immunosuppression (n = 9); (B) anti-Tac with CsA and prednisone as baseline immunosuppression (n = 12); and (C) anti-Tac with azathioprine and prednisone as baseline immunosuppression (n = 5). We found that large numbers of T cells express IL-2 receptors despite the presence of anti-Tac (average of IL-2 R-positive cells at day of peak IL-2 R expression 56.0 +/- 20.8% in group A, 65.2 +/- 26.6% in group B, 21.0 +/- 7.4% in group C). IL-2 R expression did not correlate with clinical activity, and the presence or accessibility of epitopes on the same 55 kD chain varied dramatically from patient to patient.

Decrease in phenotypically defined T helper inducer cells (T4+4B4+) and increase in T suppressor effector cells (T8+2H4+) in stable renal allograft recipients

Two monoclonal antibodies, anti-2H4 and anti-4B4, reciprocally divide the T4+ (CD4+) and T8+ (CD8+) lymphocytes into T4+2H4+, T4+4B4+, T8+2H4+ and T8+4B4+ subsets. The T4+2H4+, T4+4B4+ and T8+2H4+ subsets possess suppressor-inducer, helper-inducer, and suppressor-effector function, respectively, as previously defined in a system of B cell immunoglobulin production. Using monoclonal antibodies, including anti-2H4 and anti-4B4, and flow cytometry, we monitored lymphocyte subpopulations in 66 renal allograft recipients. We found that patients with stable allograft function have a decrease in the percentage of total T4+ lymphocytes from 41.9 +/- 9.5% pretransplant (pre-Tx) to 36.3 +/- 13.9% posttransplant (post-Tx) (P less than 0.05). This decrease was seen mainly in the T4+4B4+ or helper-inducer subset from 20.8 +/- 4.7% (pre-Tx) to 16.0 +/- 6.3% (post-Tx) (P less than 0.005). Patients with stable function were also noted to have an increase in the percentage of total T8+ lymphocytes from 21.3 +/- 10.7% (pre-Tx) to 30.9 +/- 15.4% (post-Tx) (P less than 0.02). Examination of T8 subsets revealed that a statistically significant increase was seen in the T8+2H4+ or suppressor effector subset from 15.5 +/- 9.2% (pre-Tx) to 21.5 +/- 10.2% (post-Tx) (P less than 0.01). Additionally, serial studies on 14 patients revealed an increase in the %T4+2H4+ suppressor-inducer subset from 9.31 +/- 3.64% (pre-Tx) to 15.71 +/- 6.41% (post-Tx) (P less than 0.0025). Since the role of these subsets has not been established in alloimmunity, in vitro allogeneic studies of 2H4-enriched (2H4+) and 2H4-depleted (2H4-) lymphocytes from normal peripheral blood were performed. In the mixed lymphocyte reaction, 2H4+ cells proliferated less than 2H4- cells (cpm ratio 2H4+/2H4-: 0.63-0.84), but 2H4+ cells generated twice as much suppressor activity as 2H4- cells (ratio % suppression 2H4+/2H4-: 1.9-2.3). These results suggest that 2H4+ cells play a role in the suppressor limb of the alloimmune response and that the increase in cells of this phenotype in our transplant population may be responsible for the maintenance of stable allograft function.

Association of Donor and Recipient Telomere Length with Clinical Outcomes following Lung Transplantation.

Background Patients with short telomere syndromes and pulmonary fibrosis have increased complications after lung transplant. However, the more general impact of donor and recipient telomere length in lung transplant has not been well characterized. Methods This was an observational cohort study of patients who received lung transplant at a single center between January 1st 2012 and January 31st 2015. Relative donor lymphocyte telomere length was measured and classified into long (third tertile) and short (other tertiles). Relative recipient lung telomere length was measured and classified into short (first tertile) and long (other tertiles). Outcome data included survival, need for modification of immunosuppression, liver or kidney injury, cytomegalovirus reactivation, and acute rejection. Results Recipient lung tissue telomere lengths were measured for 54 of the 79 patients (68.3%) who underwent transplant during the study period. Donor lymphocyte telomeres were measured for 45 (83.3%) of these recipients. Neither long donor telomere length (hazard ratio [HR] = 0.58, 95% confidence interval [CI], 0.12–2.85, p = 0.50) nor short recipient telomere length (HR = 1.01, 95% CI = 0.50–2.05, p = 0.96) were associated with adjusted survival following lung transplant. Recipients with short telomeres were less likely to have acute cellular rejection (23.5% vs. 58.8%, p = 0.02) but were not more likely to have other organ dysfunction. Conclusions In this small cohort, neither long donor lymphocyte telomeres nor short recipient lung tissue telomeres were associated with adjusted survival after lung transplantation. Larger studies are needed to confirm these findings.

The Presence of Pretransplant HLA Antibodies Does Not Impact the Development of Chronic Lung Allograft Dysfunction or CLAD Related Death.

Background Development of donor-specific antibodies (DSA) after lung transplantation is associated with antibody mediated rejection, acute cellular rejection, and bronchiolitis obliterans syndrome; however, the significance of circulating antibodies before transplant remains unclear. Methods We performed a retrospective cohort study including recipients of primary lung transplants between 2008 and 2012. We assessed the impact of circulating HLA and noncytotoxic DSA detected before transplant on development of Chronic Lung Allograft Dysfunction (CLAD) or CLAD-related death. Results 30% of subjects had circulating class I antibodies alone, 4% Class II, and 14.4% class I and class II at mean fluorescent intensity greater than 1000. Nine percent of the subjects had DSA class I, 9% class II, and 2.4% both DSA classes 1 and 2. Neither the presence of circulating antibodies (adjusted hazard ratio, 0.87; 95% confidence interval, 0.50-1.54) nor the presence of DSA (adjusted hazard ratio, 1.56; 95% confidence interval, 0.77-3.18) before transplant at mean fluorescent intensity greater than 1000 was associated with the development of CLAD or CLAD-related death. Conclusions Although in previous studies we have shown an increased incidence of antibody-mediated rejection in patients with pretransplant DSA, neither the presence of HLA antibodies nor DSA translated to an increased risk of allograft dysfunction or death if prospective crossmatch testing was negative. Prospective studies are needed to define the impact of pretransplant sensitization on lung transplant recipients.

Detection and clinical impact of human leukocyte antigen antibodies in lung transplantation: A systematic review and meta-analysis

There is significant variability in lung transplant centers’ approach to HLA antibodies, creating heterogeneity regarding their clinical significance. Some institutions use beads coated with multiple HLA to screen candidate sera and then use single antigen bead (SAB) to determine antibody identity if the pre‐screen is positive. Other centers do not pre‐screen, using SAB alone, which may detect low‐level antibodies of unknown significance. The primary objective of this study was to review the current literature to identify sources of heterogeneity in the identification of pre‐ and post‐lung transplant HLA antibodies, particularly regarding antibody‐detection methods. A random effects model meta‐analysis was used to evaluate the relationship between pre‐transplant HLA antibodies and the development of de novo donor‐specific antibodies (dnDSA) and dnDSA and chronic lung allograft dysfunction (CLAD). Each outcome was stratified by the method of antibody detection (pre‐screen followed by SAB vs SAB alone). We identified 13 cohort studies with a total of 3039 patients. The use of pre‐screening followed by SAB testing and the use of induction immunosuppression were associated with lower prevalence of dnDSA. Patients with pre‐transplant HLA antibodies were more likely to develop dnDSA (hazard ratio [HR] = 1.49, 95% confidence interval [CI]: 1.19‐1.86, P < .001). dnDSA was associated with CLAD (HR = 2.02, 95% CI = 1.37‐2.97, P < .001). When considering studies using SAB alone, however, pre‐transplant antibody status was no longer associated with dnDSA and dnDSA was no longer associated with CLAD. Based on the current literature, SAB‐alone testing may detect less clinically relevant antibodies than pre‐screening followed by SAB.

Antibodies against HLA-DP recognize broadly expressed epitopes

HLA matching and avoidance of pre-transplant donor-specific antibodies are important in selection of donors for solid organ transplant. Solid phase testing with single antigen beads allows resolution of antibody reactivity to the level of the allele. Single antigen bead testing results at a large transplant center were reviewed to identify selective reactivity patterns of anti-HLA antibodies. Many HLA-DP antibodies were identified in the context of other HLA antibodies, but some sera had antibodies against only HLA-DP. B cell flow crossmatch testing was positive for 2 out of 9 sera with HLA-DP antibodies. Many patterns of reactivity corresponded to epitopes in hypervariable regions C and F of DPB1, but some matched epitopes in other regions or DPA1. Through analysis of single antigen bead testing from a large number of patients, we report that anti-HLA-DP antibodies predominantly recognize broadly cross-reactive epitopes. The United Network for Organ Sharing has mandated HLA-DP typing on all deceased kidney donors, and HLA-DP epitopes should be considered as the major antigens for avoidance of pre-transplant donor-specific antibodies.