Reproducibility of Complement 4d deposition by immunofluorescence and immunohistochemistry in lung allograft biopsies

Acute rejection post lung transplant

PURPOSE OF REVIEW

To review what is currently known about the pathogenesis, diagnosis, treatment, and prevention of acute rejection (AR) in lung transplantation.

RECENT FINDINGS

Epigenomic and transcriptomic methods are gaining traction as tools for earlier detection of AR, which still remains primarily a histopathologic diagnosis.

SUMMARY

Acute rejection is a common cause of early posttransplant lung graft dysfunction and increases the risk of chronic rejection. Detection and diagnosis of AR is primarily based on histopathology, but noninvasive molecular methods are undergoing investigation. Two subtypes of AR exist: acute cellular rejection (ACR) and antibody-mediated rejection (AMR). Both can have varied clinical presentation, ranging from asymptomatic to fulminant ARDS, and can present simultaneously. Diagnosis of ACR requires transbronchial biopsy; AMR requires the additional measuring of circulating donor-specific antibody (DSA) levels. First-line treatment in ACR is increased immunosuppression (pulse-dose or tapered dose glucocorticoids); refractory cases may need antibody-based lymphodepletion therapy. First line treatment in AMR focuses on circulating DSA removal with B and plasma cell depletion; plasmapheresis, intravenous human immunoglobulin (IVIG), bortezomib, and rituximab are often employed.

Temporal correlation between postreperfusion complement deposition and severe primary graft dysfunction in lung allografts

Growing evidence implicates complement in the pathogenesis of primary graft dysfunction (PGD). We hypothesized that early complement activation postreperfusion could predispose to severe PGD grade 3 (PGD-3) at 72 hours, which is associated with worst posttransplant outcomes. Consecutive lung transplant patients (n = 253) from January 2018 through June 2023 underwent timed open allograft biopsies at the end of cold ischemia (internal control) and 30 minutes postreperfusion. PGD-3 at 72 hours occurred in 14% (35/253) of patients; 17% (44/253) revealed positive C4d staining on postreperfusion allograft biopsy, and no biopsy-related complications were encountered. Significantly more patients with PGD-3 at 72 hours had positive C4d staining at 30 minutes postreperfusion compared with those without (51% vs 12%, P < .001). Conversely, patients with positive C4d staining were significantly more likely to develop PGD-3 at 72 hours (41% vs 8%, P < .001) and experienced worse long-term outcomes. In multivariate logistic regression, positive C4d staining remained highly predictive of PGD-3 (odds ratio 7.92, 95% confidence interval 2.97-21.1, P < .001). Hence, early complement deposition in allografts is highly predictive of PGD-3 at 72 hours. Our data support future studies to evaluate the role of complement inhibition in patients with early postreperfusion complement activation to mitigate PGD and improve transplant outcomes.

Anti-CD20 Antibody and Calcineurin Inhibitor Combination Therapy Effectively Suppresses Antibody-Mediated Rejection in Murine Orthotopic Lung Transplantation

Antibody-mediated rejection (AMR) is a risk factor for chronic lung allograft dysfunction, which impedes long-term survival after lung transplantation. There are no reports evaluating the efficacy of the single use of anti-CD20 antibodies (aCD20s) in addition to calcineurin inhibitors in preventing AMR. Thus, this study aimed to evaluate the efficacy of aCD20 treatment in a murine orthotopic lung transplantation model. Murine left lung transplantation was performed using a major alloantigen strain mismatch model (BALBc (H-2d) → C57BL/6 (BL/6) (H-2b)). There were four groups: isograft (BL/6→BL/6) (Iso control), no-medication (Allo control), cyclosporine A (CyA) treated, and CyA plus murine aCD20 (CyA+aCD20) treated groups. Severe neutrophil capillaritis, arteritis, and positive lung C4d staining were observed in the allograft model and CyA-only-treated groups. These findings were significantly improved in the CyA+aCD20 group compared with those in the Allo control and CyA groups. The B cell population in the spleen, lymph node, and graft lung as well as the levels of serum donor-specific IgM and interferon γ were significantly lower in the CyA+aCD20 group than in the CyA group. Calcineurin inhibitor-mediated immunosuppression combined with aCD20 therapy effectively suppressed AMR in lung transplantation by reducing donor-specific antibodies and complement activation.

Extracellular vesicles: a potential new player in antibody-mediated rejection in lung allograft recipients

Identification of recipients with pre-existing antibodies and cross-matching of recipient sera with donor lymphocytes have reduced the incidence of antibody-mediated rejection (AMR) after human lung transplantation. However, AMR is still common and requires not only immediate intervention but also has long-term consequences including an increased risk of chronic lung allograft dysfunction (CLAD). The mechanisms resulting in AMR remain largely unknown due to the variation in clinical and histopathological features among lung transplant recipients; however, several reports have demonstrated a strong association between the development of antibodies against mismatched donor human leucocyte antigens [donor-specific antibodies (DSAs)] and AMR. In addition, the development of antibodies against lung self-antigens (K alpha1 tubulin and collagen V) also plays a vital role in AMR pathogenesis, either alone or in combination with DSAs. In the current article, we will review the existing literature regarding the association of DSAs with AMR, along with clinical diagnostic features and current treatment options for AMR. We will also discuss the role of extracellular vesicles (EVs) in the immune-related pathogenesis of AMR, which can lead to CLAD.

Antibody-Mediated Rejection: Diagnosis and Treatment

Antibody-mediated rejection (AMR) is a form of lung allograft rejection that is emerging as an important risk factor for chronic lung allograft dysfunction and decreased long-term survival. In this review, we provide a brief overview of our current understanding of its pathophysiology with an emphasis on donor-specific antibodies before moving on to focus on the current diagnostic criteria and treatment strategies. Our goal is to discuss the limitations of our current knowledge and explore how novel diagnostic and therapeutic options aim to improve outcomes through earlier definitive diagnosis and preemptive targeted treatment.

Antibodies against complement component C5 prevent antibody-mediated rejection after lung transplantation in murine orthotopic models with skin-graft-induced pre-sensitization

OBJECTIVE

Antibody-mediated rejection (AMR) could induce acute or chronic graft failure during organ transplantation. Several reports have shown that anti-C5 antibodies are effective against AMR after kidney transplantation. However, few reports have assessed the efficacy of anti-C5 antibodies against AMR after lung transplantation. Therefore, this study aimed to evaluate the efficacy of this novel therapy against AMR after lung transplantation.

METHODS

BALB/c and C57BL/6 mice were used as donors and recipients. One group was pre-sensitized (PS) by skin transplantation 14 days before lung transplantation. The other group was non-sensitized (NS). Orthotopic left-lung transplantation was performed in both groups. Animals were killed at 2 or 7 days after lung transplantation and evaluated for histopathology, C4d immunostaining, and serum donor-specific antibodies (DSAs) (n = 5 per group). Isograft (IS) models with C57BL/6 mice were used as controls. To evaluate the efficacy of C5 inhibition, other animals, which received similar treatments to those in the PS group, were treated with anti-C5 antibodies, cyclosporine/methylprednisolone, anti-C5 antibodies/cyclosporine/methylprednisolone, or isotype-matched irrelevant control monoclonal antibodies (n = 5 per group).

RESULTS

Two days after lung transplantation, the NS group exhibited mild, localized graft-rejection features (rejection score: 0.45 ± 0.08, p = 0.107). The PS group exhibited AMR features with a significantly higher rejection score (2.29 ± 0.42, p = 0.001), C4d vascular-endothelium deposition, and substantial presence of serum DSA. On day 7 after lung transplantation, both groups showed extensive graft alveolar wall destruction, and high acute-rejection scores. Mice receiving anti-C5 antibodies or anti-C5/antibodies/cyclosporine/methylprednisolone demonstrated significantly lower acute-rejection scores (0.63 ± 0.23, p = 0.002; 0.59 ± 0.22, p = 0.001, respectively) than those receiving isotype control antibodies.

CONCLUSIONS

Murine orthotopic allograft lung transplant models met the clinical diagnosis and pathogenesis classification criteria of AMR. In these models, anti-C5 antibodies suppressed AMR. Therefore, anti-C5 therapy may be effective against AMR after lung transplantation.

Effects of shikonin on the development of ovarian follicles and female germline stem cells

Objective

To investigate the effects and potential mechanism of action of shikonin (SHK) on the development of ovarian follicles and female germline stem cells (FGSCs).

Methods

Female Kunming adult mice were administered SHK (0, 20 and 50 mg/kg) by oral gavage. Cultures of FGSCs were treated with SHK 32 μmol/l for 24 h. The ovarian index in mouse ovaries was calculated. Numbers of primordial, primary and atretic follicles were counted. Germline stem cell markers and apoptosis were examined. Levels of glutathione (GSH), superoxide dismutase (SOD) and reactive oxygen species (ROS) were measured.

Results

Both doses of SHK significantly decreased the ovarian index, the numbers of primordial follicles, primary follicles and antral follicles in mice. SHK significantly increased the numbers of atretic follicles and atretic corpora lutea. SHK promoted apoptosis in vivo and in vitro. SHK significantly decreased the levels of the germline stem cell markers. SHK significantly lowered GSH levels and the activity of SOD in the peripheral blood from mice, whereas SHK significantly elevated cellular ROS content in FGSCs.

Conclusions

These current results suggested that follicular development and FGSCs were suppressed by SHK through the induction of apoptosis and oxidative stress might be involved in this pathological process.

Phosphorylated S6 ribosomal protein expression by immunohistochemistry correlates with de novo donor-specific HLA antibodies in lung allograft recipients

BACKGROUND

Per the ISHLT 2016 definition, a C4d-positive lung biopsy is required to meet criteria for definite antibody-mediated rejection (AMR). Unfortunately, C4d has poor sensitivity and specificity, and low inter-rater reliability. Phosphorylated S6 ribosomal protein (p-S6RP) expressed via the mTOR pathway has been shown to be a biomarker of AMR and correlates with donor-specific antibodies (DSA) in heart allografts. However, p-S6RP immunohistochemistry (IHC) in the setting of pulmonary AMR has yet to be evaluated. We sought to determine whether p-S6RP IHC performed on lung biopsies correlates with de novo DSA.

METHODS

IHC for p-S6RP performed on 26 biopsies from lung transplant recipients with de novo HLA DSA (DSA+) and 28 biopsies from patients with no DSA (DSA-) were evaluated by 3 pathologists who independently scored the degree of alveolar macrophage and pneumocyte staining. Staining in ≥50% of the biopsy as determined by at least 2 pathologists was considered positive.

RESULTS

Twenty-one (81%) DSA+ biopsies stained positive for p-S6RP in pneumocytes and 21 (81%) in macrophages. Six DSA- biopsies (21%) stained positive for p-S6RP in pneumocytes, 6 (21%) were positive in macrophages. Pneumocyte p-S6RP staining was 81% sensitive and 79% specific for DSA. Macrophage staining showed the same sensitivity and specificity but with lower inter-rater agreement (κ = 0.53 vs 0.68).

CONCLUSIONS

This study demonstrates a positive relationship between de novo DSA and p-S6RP expression in pneumocytes and macrophages using IHC. p-S6RP is relatively sensitive and specific, and has superior inter-rater reliability compared to C4d.

Antibody-Mediated Rejection and Lung Transplantation

Antibody-mediated rejection (AMR) is now a widely recognized form of lung allograft rejection, with mounting evidence for AMR as an important risk factor for the development of chronic lung allograft dysfunction and markedly decreased long-term survival. Despite the recent development of the consensus diagnostic criteria, it remains a challenging diagnosis of exclusion. Furthermore, even after diagnosis, treatment directed at pulmonary AMR has been nearly exclusively derived from practices with other solid-organ transplants and other areas of medicine, such that there is a significant lack of data regarding the efficacy for these in pulmonary AMR. Lastly, outcomes after AMR remain quite poor despite aggressive treatment. In this review, we revisit the history of AMR in lung transplantation, describe our current understanding of its pathophysiology, discuss the use and limitations of the consensus diagnostic criteria, review current treatment strategies, and summarize long-term outcomes. We conclude with a synopsis of our most pressing gaps in knowledge, introduce recommendations for future directions, and highlight promising areas of active research.

Assessment of Carfilzomib Treatment Response in Lung Transplant Recipients With Antibody-mediated Rejection

Supplemental Digital Content is available in the text.

Data supporting the use of carfilzomib (CFZ) for treatment of antibody-mediated rejection (AMR) in lung transplantation in combination with plasmapheresis and intravenous immunoglobulin suggest positive outcomes through donor-specific antibody (DSA) depletion or conversion to noncomplement-activating antibodies. Herein, we describe our center’s experience treating AMR with CFZ.

Lung Transplant Pathology: An Overview on Current Entities and Procedures

Alloimmune reactions are, besides various infections, the major cause for impaired lung allograft function following transplant. Acute cellular rejection is not only a major trigger of acute allograft failure but also contributes to development of chronic lung allograft dysfunction. Analogous to other solid organ transplants, acute antibody-mediated rejection has become a recognized entity in lung transplant pathology. Adequate sensitivity and specificity in the diagnosis of alloimmune reactions in the lung can only be achieved by synoptic analysis of histopathologic, clinical, and radiological findings together with serologic and microbiologic findings.

Free Airway C4d after Lung Transplantation - A Quantitative Analysis of Bronchoalveolar Lavage Fluid

In recent years, the utility of vascular complement factor 4d (C4d) deposition as diagnostic tool for antibody mediated rejection (AMR) after lung transplantation, has become a controversial issue. We aimed to pinpoint the problematic nature of C4d as biomarker with a simple experiment. We quantified C4d in broncho-alveolar lavage (BAL) of lung transplant patients with diverse post-transplant complications in 3 different settings of clinically clear cases of: 1/ chronic lung allograft dysfunction (CLAD); 2/ acute complications acute rejection (AR), lymphocytic bronchiolitis (LB), antibody-mediated rejection (AMR) and respiratory infection (INF); 3/ patients with parallel C4d immunostaining and Anti-HLA. All groups were compared to BAL of stable patients. C4d was measured via standard ELISA. C4d was increased in CLAD, predominantly in RAS (p = 0.0026) but not in BOS (p = 0.89). C4d was increased in all acute events, AR (p = 0.0025), LB (p < 0.0001), AMR (p = 0.0034), infections (p < 0.0001). In patients with parallel C4d immunostaining and serum HLA antibodies, C4d was increased in C4d-/HLA- (p = 0.0011); C4d-/HLA+ (p = 0.013); HLA+/C4d + (p = 0.0081). A correlation of systemic C-reactive protein (CRP) with C4d was found in all patients (r = 0.49; p < 0.0001). We hypothesize that free C4d in BAL may only be representative of a general immune response in the transplanted lung.

When tissue is the issue: A histological review of chronic lung allograft dysfunction

Although chronic lung allograft dysfunction (CLAD) remains the major life-limiting factor following lung transplantation, much of its pathophysiology remains unknown. The discovery that CLAD can manifest both clinically and morphologically in vastly different ways led to the definition of distinct subtypes of CLAD. In this review, recent advances in our understanding of the pathophysiological mechanisms of the different phenotypes of CLAD will be discussed with a particular focus on tissue-based and molecular studies. An overview of the current knowledge on the mechanisms of the airway-centered bronchiolitis obliterans syndrome, as well as the airway and alveolar injuries in the restrictive allograft syndrome and also the vascular compartment in chronic antibody-mediated rejection is provided. Specific attention is also given to morphological and molecular markers for early CLAD diagnosis or histological changes associated with subsequent CLAD development. Evidence for a possible overlap between different forms of CLAD is presented and discussed. In the end, "tissue remains the (main) issue," as we are still limited in our knowledge about the actual triggers and specific mechanisms of all late forms of posttransplant graft failure, a shortcoming that needs to be addressed in order to further improve the outcome of lung transplant recipients.

The impact of C4d testing on tissue adequacy in lung transplant surveillance

BACKGROUND

Surveillance transbronchial biopsies are routinely used to assess lung allograft rejection. While the criteria for diagnosing acute cellular rejection have been well-established, the morphological findings associated with antibody mediated rejection are variable. To increase the sensitivity for antibody mediated rejection, a portion of a biopsy can be used for C4d immunofluorescence testing, along with histologic findings and donor specific antibodies. When the number of alveolar pieces in a biopsy is small, the relative utility of sending one piece for C4d testing is unclear.

METHODS

Pathology reports of 1400 surveillance transbronchial lung biopsies from 2008 to 2017 were reviewed to obtain the number of pieces of alveolar parenchyma in each case. Based on a standard definition of adequacy as five pieces of well-expanded alveolar parenchyma, reports with five fragments were grouped as "adequate", four pieces as a "marginal" sample, and three or less were considered an "inadequate" sample.

RESULTS

Of the 1400 biopsies, 653 specimens had 5 or more pieces of alveolar parenchyma.747 specimens were submitted with less than 5 pieces and 290 of those were considered marginal. In all marginal cases, a piece was withheld for C4d immunofluorescence testing.

CONCLUSIONS

About 21% of specimens would have the recommended 5 pieces of alveolar parenchyma if not for the withholding of pieces for C4d IF testing. Over the span of 10 years, 290 such cases were recorded at our institution. Given this nontrivial impact, it is unclear if C4d immunofluorescence testing should be performed on surveillance transbronchial biopsies when the number of pieces in the specimen is marginal.

Antibody-mediated rejection after lung transplantation

Antibody-mediated rejection (AMR) has been identified as a significant form of acute allograft dysfunction in lung transplantation. The development of consensus diagnostic criteria has created a uniform definition of AMR; however, significant limitations of these criteria have been identified. Treatment modalities for AMR have been adapted from other areas of medicine and data on the effectiveness of these therapies in AMR are limited. AMR is often refractory to these therapies, and graft failure and death are common. AMR is associated with increased rates of chronic lung allograft dysfunction (CLAD) and poor long-term survival. In this review, we discuss the history of AMR and describe known mechanisms, application of the consensus diagnostic criteria, data for current treatment strategies, and long-term outcomes. In addition, we highlight current gaps in knowledge, ongoing research, and future directions to address these gaps. Promising diagnostic techniques are actively being investigated that may allow for early detection and treatment of AMR. We conclude that further investigation is required to identify and define chronic and subclinical AMR, and head-to-head comparisons of currently used treatment protocols are necessary to identify an optimal treatment approach. Gaps in knowledge regarding the epidemiology, mechanisms, diagnosis, and treatment of AMR continue to exist and future research should focus on these aspects.

Ultrastructural changes in pulmonary allografts with antibody-mediated rejection

BACKGROUND

Antibody-mediated rejection (AMR) is an important cause of lung allograft loss in some patients. Challenges with current diagnostic criteria limit timely detection. Ultrastructural studies of endothelia allow the early detection of AMR in kidney allografts. This study aimed to define the ultrastructural changes of the endothelium in lung allografts in the setting of AMR and determine its specificity for AMR.

METHODS

Ultrastuctural studies were performed on lung allograft biopsies of 12 patients using glutaraldehyde-fixed or paraffin-embedded material. AMR had been classified according to the International Society of Heart and Lung Transplant 2016 consensus report criteria. Endothelial changes (swelling [ES], vacuolization [EV], surface irregularity, detachment, neutrophil margination [NM]) and basement membrane changes were graded semi quantitatively using electron microscopy (EM). Grades were compared between AMR, acute cellular rejection, and non-transplant controls.

RESULTS

Significant differences were found between AMR and acute cellular reaction biopsies, particularly in ES (p = 0.006), EV (p = 0.023) and NM (p = 0.038). Using a combined score of all categories of assessment, the total EM score was significantly higher in AMR (p = 0.007) and provided excellent sensitivity and specificity with a receiver operator characteristic curve of 1.0. C4d did not correlate with EM changes associated with AMR. The use of paraffin-embedded material samples did not significantly affect the analysis compared with glutaraldehyde-fixed tissue, although ES was reduced in the former.

CONCLUSIONS

Endothelial structural analysis using EM can facilitate improved diagnostic accuracy of AMR and needs to be validated in larger cohorts, but it also allows retrospective studies to be performed.

Intragraft donor-specific anti-HLA antibodies in phenotypes of chronic lung allograft dysfunction

INTRODUCTION

Circulating anti-human leukocyte antigen (HLA) serum donor-specific antibodies (sDSAs) increase the risk of chronic lung allograft dysfunction (CLAD) and mortality. Discrepancies between serological and pathological/clinical findings are common. Therefore, we aimed to assess the presence of tissue-bound graft DSAs (gDSAs) in CLAD explant tissue compared with sDSAs.

METHODS

Tissue cores, obtained from explant lungs of unused donors (n=10) and patients with bronchiolitis obliterans syndrome (BOS; n=18) and restrictive allograft syndrome (RAS; n=18), were scanned with micro-computed tomography before elution of antibodies. Total IgG levels were measured via ELISA. Anti-HLA class I and II IgG gDSAs were identified using Luminex single antigen beads and compared with DSAs found in serum samples.

RESULTS

Overall, mean fluorescence intensity was higher in RAS eluates compared with BOS and controls (p<0.0001). In BOS, two patients were sDSA⁺/gDSA⁺ and two patients were sDSA^-/gDSA⁺. In RAS, four patients were sDSA⁺/gDSA⁺, one patient was sDSA⁺/gDSA^- and five patients were sDSA^-/gDSA⁺. Serum and graft results combined, DSAs were more prevalent in RAS compared with BOS (56% versus 22%; p=0.04). There was spatial variability in gDSA detection in one BOS patient and three RAS patients, who were all sDSA^-. Total graft IgG levels were higher in RAS than BOS (p<0.0001) and in gDSA⁺ versus gDSA^- (p=0.0008), but not in sDSA⁺ versus sDSA^- (p=0.33). In RAS, total IgG levels correlated with fibrosis (r= -0.39; p=0.02).

CONCLUSIONS

This study underlines the potential of gDSA assessment as complementary information to sDSA findings. The relevance and applications of gDSAs need further investigation.

FCGR3A and FCGR2A Genotypes Differentially Impact Allograft Rejection and Patients' Survival After Lung Transplant

Fc gamma receptors (FcγRs) play a major role in the regulation of humoral immune responses. Single-nucleotide polymorphisms (SNPs) of FCGR2A and FCGR3A can impact the expression level, IgG affinity and function of the CD32 and CD16 FcγRs in response to their engagement by the Fc fragment of IgG. The CD16 isoform encoded by FCGR3A [158V/V] controls the intensity of antibody-dependent cytotoxic alloimmune responses of natural killer cells (NK) and has been identified as a susceptibility marker predisposing patients to cardiac allograft vasculopathy after heart transplant. This study aimed to investigate whether FCGR2A and FCGR3A polymorphisms can also be associated with the clinical outcome of lung transplant recipients (LTRs). The SNPs of FCGR2A ([131R/H], rs1801274) and FCGR3A ([158V/F], rs396991) were identified in 158 LTRs and 184 Controls (CTL). The corresponding distribution of genotypic and allelic combinations was analyzed for potential links with the development of circulating donor-specific anti-HLA alloantibodies (DSA) detected at months 1 and 3 after lung transplant (LTx), the occurrence of acute rejection (AR) and chronic lung allograft dysfunction (CLAD), and the overall survival of LTRs. The FCGR3A [158V/V] genotype was identified as an independent susceptibility factor associated with higher rates of AR during the first trimester after LTx (HR 4.8, p < 0.0001, 95% CI 2.37-9.61), but it could not be associated with the level of CD16- mediated NK cell activation in response to the LTR's DSA, whatever the MFI intensity and C1q binding profiles of the DSA evaluated. The FCGR2A [131R/R] genotype was associated with lower CLAD-free survival of LTRs, independently of the presence of DSA at 3 months (HR 1.8, p = 0.024, 95% CI 1.08-3.03). Our data indicate that FCGR SNPs differentially affect the clinical outcome of LTRs and may be of use to stratify patients at higher risk of experiencing graft rejection. Furthermore, these data suggest that in the LTx setting, specific mechanisms of humoral alloreactivity, which cannot be solely explained by the complement and CD16-mediated pathogenic effects of DSA, may be involved in the development of acute and chronic lung allograft rejection.

C4d detection and histological patterns in the diagnosis of antibody-mediated rejection after lung transplantation: a single-centre study

AIMS

Antibody-mediated rejection (AMR) is an emerging and challenging issue in transplantation. Endothelial deposition of C4d and microvascular inflammation (MI) are reliable markers of AMR in renal and cardiac transplantation, but remain controversial in the lung. Our aim was to assess C4d immunohistochemistry and histological patterns for the diagnosis of lung AMR.

METHODS AND RESULTS

We reviewed 158 transbronchial biopsies (TBBs) (n = 85 clinically indicated, and n = 73 surveillance TBBs) from 48 recipients, blinded to clinical and serological data. C4d was scored as 0, 1+ (<10%), 2+ (10-50%) or 3+ (>50%). TBBs were reassessed for MI and acute lung injury (ALI). Donor-specific antibodies (DSAs), acute clinical graft dysfunction and chronic lung allograft graft dysfunction (CLAD) were recorded. C4d3+, C4d2+, C4d1+ and C4d0 occurred respectively in four (2.5%), six (3.8%), 28 (17.7%) and 120 (75.9%) TBBs. MI and ALI were rare but more frequent in C4d1-3+ TBBs than in the absence of C4d. C4d2+ was frequently observed with concomitant infection. Among the surveillance TBBs, only two (2.7%) showed MI. Neither ALI nor C4d3+ was diagnosed on surveillance TBBs. No significant association was found between histopathological findings and DSAs. All four patients with C4d3+ could retrospectively be diagnosed with AMR and developed CLAD.

CONCLUSION

Although rare, diffuse C4d deposition appears to be a strong indication of acute clinical AMR in lung transplant patients, whereas intermediate C4d2+ requires more investigations. In stable patients, histopathology and C4d may lack the sensitivity to diagnose subclinical AMR. This emphasises the need for a multidisciplinary evaluation of each suspected AMR case, and the need for complementary diagnostic tools.

Evaluation of current strategies for surveillance and management of donor-specific antibodies: Single-center study

BACKGROUND

Although the presence of donor-specific antibodies (DSA) is known to impact lung allograft, limited data exist regarding DSA management.

METHODS

We did a retrospective study at our center evaluating DSA management in adult lung transplant recipients undergoing lung transplantation between January 1, 2010 and June 30, 2014. Study follow-up was completed through October 2017. All recipients were stratified into 2 groups based on the presence or absence of DSA. Those with DSA were evaluated for the impact of treatment of DSA. The primary outcomes were postlung transplant survival and freedom from bronchiolitis obliterans syndrome (BOS), subset of chronic lung allograft dysfunction (CLAD). Simon-Makuch method was used to estimate overall survival and BOS-free survival to account for DSA as time-dependent covariate. Survival differences between the groups were analyzed using time-dependent Cox proportional hazards model.

RESULTS

Sixty-four percent of 194 total subjects developed post-lung transplant DSA. Overall survival was different with worse survival in the DSA positive group that never cleared DSA (P = .002). BOS-free survival was lower, but did not reach significance in this group. Response to treatment was poor, with only 12 of 47 (25.5%) who received treatment demonstrating clearance of DSA.

CONCLUSIONS

Donor-specific antibodies prevalence is high after lung transplantation. Clearance of DSA correlated with improved outcomes. Current therapeutic strategies against DSA are relatively ineffective. Multicenter collaborative studies will be required to evaluate current treatment strategies and other innovative modalities.

The role of C4d deposition in the diagnosis of antibody-mediated rejection after lung transplantation

Antibody-mediated rejection (AMR) is an increasingly recognized form of lung rejection. C4d deposition has been an inconsistent finding in previous reports and its role in the diagnosis has been controversial. We conducted a retrospective single-center study to characterize cases of C4d-negative probable AMR and to compare these to cases of definite (C4d-positive) AMR. We identified 73 cases of AMR: 28 (38%) were C4d-positive and 45 (62%) were C4d-negative. The two groups had a similar clinical presentation, and although more patients in the C4d-positive group had neutrophilic capillaritis (54% vs. 29%, P = .035), there was no significant difference in the presence of other histologic findings. Despite aggressive antibody-depleting therapy, 19 of 73 (26%) patients in the overall cohort died within 30 days, but there was no significant difference in freedom from chronic lung allograft dysfunction (CLAD) or survival between the two groups. We conclude that AMR may cause allograft failure, but that the diagnosis requires a multidisciplinary approach and a high index of suspicion. C4d deposition does not appear to be a necessary criterion for the diagnosis, and although some cases may respond initially to therapy, there is a high incidence of CLAD and poor survival after AMR.

Pathology of Lung Rejection: Cellular and Humoral Mediated

Acute rejection is an important risk factor for bronchiolitis obliterans syndrome, the clinical manifestation of chronic airway rejection in lung allograft recipients. Patients with acute rejection might be asymptomatic or present with symptoms that are not specific and can be also seen in other conditions. Clinical tests such as pulmonary function tests and imaging studies among others usually are abnormal; however, their results are also not specific for acute rejection. Histopathologic features of acute rejection in adequate samples of transbronchial lung biopsy of the lung allograft are currently the gold standard to assess for acute rejection in lung transplant recipients. Acute alloreactive injury can affect both the vasculature and the airways. Currently, the guidelines of the 2007 International Society of Heart and Lung Transplantation consensus conference are recommended for the histopathologic assessment of rejection. There are no specific morphologic features recognized to diagnose antibody-mediated rejection (AMR) in lung allografts. Therefore, the diagnosis of AMR currently requires a “triple test” including clinical features, serologic evidence of donor-specific antibodies, and pathologic findings supportive of AMR. Complement 4d deposition is used to support a diagnosis of AMR in many solid organ transplants; however, its significance for the diagnosis of AMR in lung allografts is not entirely clear. This chapter discusses the currently recommended guidelines for the assessment of cellular rejection of lung allografts and summarizes our knowledge about morphologic features and immunophenotypic tests that might help in the diagnosis of AMR.

Acute rejection

Despite induction immunosuppression and the use of aggressive maintenance immunosuppressive regimens, acute allograft rejection following lung transplantation is still a problem with important diagnostic and therapeutic challenges. As well as causing early graft loss and mortality, acute rejection also initiates the chronic alloimmune responses and airway-centred inflammation that predispose to bronchiolitis obliterans syndrome (BOS), also known as chronic lung allograft dysfunction (CLAD), which is a major source of morbidity and mortality after lung transplantation. Cellular responses to human leukocyte antigens (HLAs) on the allograft have traditionally been considered the main mechanism of acute rejection, but the influence of humoral immunity is increasingly recognised. As with other several other solid organ transplants, antibody-mediated rejection (AMR) is now a well-accepted and distinct clinical entity in lung transplantation. While acute cellular rejection (ACR) has defined histopathological criteria, transbronchial biopsy is less useful in AMR and its diagnosis is complicated by challenges in the measurement of antibodies directed against donor HLA, and a determination of their significance. Increasing awareness of the importance of non-HLA antigens further clouds this issue. Here, we review the pathophysiology, diagnosis, clinical presentation and treatment of ACR and AMR in lung transplantation, and discuss future potential biomarkers of both processes that may forward our understanding of these conditions.

Diagnosis of Acute Cellular Rejection and Antibody-Mediated Rejection on Lung Transplant Biopsies: A Perspective From Members of the Pulmonary Pathology Society

Context.—

The diagnosis and grading of acute cellular and antibody-mediated rejection (AMR) in lung allograft biopsies is important because rejection can lead to acute graft dysfunction and/or failure and may contribute to chronic graft failure. While acute cellular rejection is well defined histologically, no reproducible specific features of AMR are currently identified. Therefore, a combination of clinical features, serology, histopathology, and immunologic findings is suggested for the diagnosis of AMR.

Objective.—

To describe the perspective of members of the Pulmonary Pathology Society (PPS) on the workup of lung allograft transbronchial biopsy and the diagnosis of acute cellular rejection and AMR in lung transplant.

Data Sources.—

Reports by the International Society for Heart and Lung Transplantation (ISHLT), experience of members of PPS who routinely review lung allograft biopsies, and search of literature database (PubMed).

Conclusions.—

Acute cellular rejection should be assessed and graded according to the 2007 working formulation of the ISHLT. As currently no specific features are known for AMR in lung allografts, the triple test (clinical allograft dysfunction, donor-specific antibodies, pathologic findings) should be used for its diagnosis. C4d staining might be performed when morphologic, clinical, and/or serologic features suggestive of AMR are identified.

Lung Transplantation: The State of the Airways

CONTEXT

Lung transplantation has become a viable option for definitive treatment of several end-stage lung diseases for which there are no other options available. However, long-term survival continues to be limited by chronic lung allograft dysfunction, which primarily affects the airways.

OBJECTIVE

To highlight the complications occurring mainly in the airways of the lung transplant recipient from the early to late posttransplant periods.

DATA SOURCES

Review literature focusing on the airways in patients with lung transplants and clinical experience of the authors.

CONCLUSIONS

Postsurgical complications and infections of the airways have decreased because of better techniques and management. Acute cellular rejection of the airways can be distinguished from infection pathologically and on cultures. Separating small from large airways need not be an issue because both are risk factors for bronchiolitis obliterans. Grading of airway rejection needs to be standardized. Chronic lung allograft dysfunction consists of both bronchiolitis obliterans and restrictive allograft syndrome, neither of which can be treated very effectively at present.

Antibody-mediated rejection of the lung: A consensus report of the International Society for Heart and Lung Transplantation

Antibody-mediated rejection (AMR) is a recognized cause of allograft dysfunction in lung transplant recipients. Unlike AMR in other solid-organ transplant recipients, there are no standardized diagnostic criteria or an agreed-upon definition. Hence, a working group was created by the International Society for Heart and Lung Transplantation with the aim of determining criteria for pulmonary AMR and establishing a definition. Diagnostic criteria and a working consensus definition were established. Key diagnostic criteria include the presence of antibodies directed toward donor human leukocyte antigens and characteristic lung histology with or without evidence of complement 4d within the graft. Exclusion of other causes of allograft dysfunction increases confidence in the diagnosis but is not essential. Pulmonary AMR may be clinical (allograft dysfunction which can be asymptomatic) or sub-clinical (normal allograft function). This consensus definition will have clinical, therapeutic and research implications.

Antibody-mediated rejection

PURPOSE OF REVIEW

Pulmonary antibody-mediated rejection (AMR) while contributing to acute and chronic allograft dysfunction remains a diagnostic and therapeutic challenge. The diagnostic tenets upon which AMR is defined will be reviewed in the light of recent studies.

RECENT FINDINGS

The introduction of solid phase assays such as the Luminex platform has provided a wealth of quantitative data on the presence of anti-human leukocyte antigen (HLA) donor-specific antibodies (DSA). Further studies are required to better define the relationship of circulating DSA and activation of proinflammatory immune pathways that result in allograft dysfunction. The limitations of C4d staining in defining AMR are highlighted from recent studies in lung transplantation and from the 2013 Banff meeting on renal transplantation.

SUMMARY

The current challenge to the lung transplant community is to agree on a working definition of pulmonary AMR. Only then can we better appreciate the epidemiology, clinical phenotypes, and treatment of AMR.

Practical Applications in Immunohistochemistry: Evaluation of Rejection and Infection in Organ Transplantation

CONTEXT

-Immunohistochemical analysis of tissue biopsy specimens is a crucial tool in diagnosis of both rejection and infection in patients with solid organ transplants. In the past 15 years, the concept of antibody-mediated rejection has been refined, and diagnostic criteria have been codified in renal, heart, pancreas, and lung allografts (with studies ongoing in liver, small intestine, and composite grafts), all of which include immunoanalysis for the complement split product C4d.

OBJECTIVES

-To review the general concepts of C4d biology and immunoanalysis, followed by organ-allograft-specific data, and interpretative nuances for kidney, pancreas, and heart, with discussion of early literature for lung and liver biopsies. Additionally, practical applications and limitations of immunostains for infectious organisms (Polyomavirus, Adenoviridae [adenovirus], and the herpes virus family, including Herpes simplex virus, Cytomegalovirus, Human herpes virus 8, and Epstein-Barr virus) are reviewed in the context of transplant recipients.

DATA SOURCES

-Our experience and published primary and review literature.

CONCLUSIONS

-Immunohistochemistry continues to have an important role in transplant pathology, most notably C4d staining in assessment of antibody-mediated rejection and assessment of viral pathogens in tissue. In all facets of transplant pathology, correlation of morphology with special studies and clinical data is critical, as is close communication with the transplant team.

Antibody-mediated Rejection in Lung Transplantation

There has been increasing awareness of antibody-mediated rejection (AMR) as an important cause of graft failure after lung transplantation in recent years. However, the diagnostic criteria for pulmonary AMR are not well defined. All four tenets of AMR in kidney and heart transplantation, graft dysfunction, complement component deposition, circulating donor-specific antibodies (DSA), and histopathologic changes consistent with AMR, are infrequently present in lung transplantation. Nonetheless, the lung transplant community has made important progress recognizing cases of AMR and developing a definition. However, AMR is often refractory to therapy resulting in graft failure and death. In this review, we discuss the progress and challenges in the diagnosis and therapeutic options for pulmonary AMR. In addition, we briefly examine emerging paradigms of C4d-negative AMR and chronic AMR, and conclude that significant progress is needed to mitigate the effects of humoral immune responses after lung transplantation.

Transbronchial Cryobiopsies in the Evaluation of Lung Allografts: Do the Benefits Outweigh the Risks?

CONTEXT

Transbronchial cryobiopsy technique yields larger biopsies with enhanced quality. The benefits and safety of cryobiopsies have not been thoroughly studied in lung allografts.

OBJECTIVE

To compare size, quality, reproducibility of interpretation of rejection and complications of cryobiopsies with those of conventional biopsies from lung allografts.

DESIGN

All cryobiopsies (March 2014-January 2015) of lung allografts performed at Mayo Clinic, Rochester, and medical records were reviewed. For comparison, conventional biopsies from the same patient or, if unavailable, from a random patient, were selected. Two pathologists blinded to outcome reviewed all biopsies. Specimen volume, number of alveoli, small airways, and pulmonary vessels were counted and statistically compared.

RESULTS

Fifty-four biopsies (27 cryobiopsies) from 18 patients (11 men) were reviewed. A median of 3 (range, 2-5) and 10 (range, 6-12) specimens were obtained with cryobiopsies and conventional biopsies, respectively. Cryobiopsies were larger and contained more alveoli (P < .001, both) and small airways (P = .04). Conventional biopsies showed more fresh alveolar hemorrhage (procedural) and crush artifact/atelectasis (P < .001, both). Cryobiopsies contained more pulmonary veins and venules (P < .001). There was no significant difference between the types of biopsies with respect to the reviewers' agreement on grades of rejection. Complications were more frequent in the cryobiopsy group, though the difference was not statistically significant.

CONCLUSIONS

Cryobiopsies of lung allografts are larger and have less artifact. However, complications occur and should be considered. Three cryobiopsy specimens appear sufficient for histopathologic evaluation of lung allografts.