Peripheral blood eosinophilia as a marker of acute cellular rejection in lung transplant recipients

Systematic Reporting of Eosinophils in Transbronchial Biopsies After Lung Transplantation Defines a Distinct Inflammatory Response

BACKGROUND

Descriptions of eosinophils in transbronchial biopsy (TBBx) pathology reports after lung transplantation (LTx) are associated with poor long-term outcomes. The absence of routine reporting and standardization precludes accurate assessment of this histologic predictor. A systematic reporting scheme for the presence of TBBx eosinophils after LTx was implemented. This report aims to assess this scheme by describing the presence, pattern, and gradation of TBBx eosinophils and clinical associations.

METHODS

A prospective cross-sectional study of all TBBx reports was performed including all patients presenting for a surveillance or diagnostic TBBx between January 2020 and June 2023. Each TBBx was systematically reported in a blinded manner. Mixed-effects logistic regression was performed to measure the association between concurrent clinical and histologic features, and the presence of TBBx eosinophils.

RESULTS

A total of 410 TBBx reports from 201 patients were systematically reported. In 43.8% recipients, any TBBx eosinophils were detected and in 17.1% recipients, higher-grade eosinophils (≥3 per high power field) were present. Adjusted analysis showed that retransplantation, A- and B-grade cellular rejection, positive bronchoalveolar lavage (BAL) bacterial microbiology, and elevated blood eosinophil count were independently associated with the presence of any TBBx eosinophils. Diagnostic "for-cause" procedures were independently associated with higher quantities of TBBx eosinophils.

CONCLUSIONS

Systematic reporting demonstrates that TBBx eosinophils are a distinct inflammatory response associated with rejection, infection, and peripheral eosinophilia. Although these findings require multicenter external validation, standardized reporting for TBBx eosinophils may assist in identifying recipients at risk of poor outcomes and provides a platform for mechanistic research into their role after lung transplantation.

Clinical Outcomes in Delayed Sternal Closure in Lung Transplantation

INTRODUCTION

Lung transplantation (LTx) is a critical treatment for end-stage pulmonary diseases. Delayed sternal closure (DSC) has been noted in cardiac surgery for several decades and is a viable strategy for patients who are hemodynamically unstable, at high risk for postoperative bleeding, and/or require prolonged cardiopulmonary bypass. However, DSC use and its effects on LTx clinical outcomes are not well-defined.

METHODS

A retrospective analysis was performed on patients who had undergone LTx between January 1, 2010, and October 1, 2018, at the University of Washington. Patients under the age of 18, undergoing repeat LTx, other solid organ transplantation, and/or had prior major cardiothoracic surgery were excluded. Patients were classified into 2 categories: DSC and primary sternal closure (PSC) groups. We examined hospital length of stay (LOS), intensive care unit (ICU) LOS, duration on the ventilator, and overall survival.

RESULTS

A total of 370 patients were identified, with 350 patients in the PSC group and 20 patients in the DSC group. The median hospital LOS, ICU LOS and duration on the ventilator in the DSC group were 23.0 ± 3.8, 16.0 ± 3.6, and 9.0 ± 3.5 compared with 15.0 ± 0.8, 5.0 ± 0.5, and 1.0 ± 0.3 in the PSC group, respectively (All P < .01). Kaplan-Meier analysis revealed that, at 1, 3, and 5 years, the DSC group had a survival of 75.0%, 60.0%, and 55.0%, and the PSC group had a survival of 91.4%, 82.6% and 75.1% respectively (P = .019).

CONCLUSION

DSC is not uncommon in LTx and patients who do require DSC had a longer duration on the ventilator, ICU LOS, and hospital LOS. Additionally, the DSC group had a worse survival compared with the PSC group. DSC is unlikely to be the sole factor influencing worse survival, but may be a marker of underlying patient factors that negatively affect survival.

The ability of an electronic nose to distinguish between complications in lung transplant recipients

Complications like acute cellular rejection (ACR) and infection are known risk factors for the development of chronic lung allograft dysfunction, impacting long-term patient and graft survival after lung transplantation (LTx). Differentiating between complications remains challenging and time-sensitive, highlighting the need for accurate and rapid diagnostic modalities. We assessed the ability of exhaled breath analysis using an electronic nose (eNose) to distinguish between ACR, infection, and mechanical complications in LTx recipients (LTR) presenting with suspected complications. LTR with suspected complications and subsequently proven diagnosis underwent exhaled breath analysis using an eNose. Supervised machine learning was used to assess the eNose's ability to discriminate between complications. Next, we determined the added value of the eNose measurement on top of standard clinical parameters. In 90 LTR, 161 measurements were performed during suspected complications, with 84 proven diagnoses. The eNose could distinguish between ACR, infection, and mechanical complications with 74% accuracy, and ACR and infection with 82% accuracy. Combining eNose measurements with standard clinical parameters improved diagnostic accuracy to 88% (P =.0139), with 94% sensitivity and 80% specificity. Exhaled breath analysis using eNose technology is a promising, noninvasive, diagnostic modality for distinguishing LTx complications, enabling timely diagnosis and interventions.

BAL Fluid Eosinophilia Associates With Chronic Lung Allograft Dysfunction Risk: A Multicenter Study

BACKGROUND

Chronic lung allograft dysfunction (CLAD) is the leading cause of death among lung transplant recipients. Eosinophils, effector cells of type 2 immunity, are implicated in the pathobiology of many lung diseases, and prior studies suggest their presence associates with acute rejection or CLAD after lung transplantation.

RESEARCH QUESTION

Does histologic allograft injury or respiratory microbiology correlate with the presence of eosinophils in BAL fluid (BALF)? Does early posttransplant BALF eosinophilia associate with future CLAD development, including after adjustment for other known risk factors?

STUDY DESIGN AND METHODS

We analyzed BALF cell count, microbiology, and biopsy data from a multicenter cohort of 531 lung recipients with 2,592 bronchoscopies over the first posttransplant year. Generalized estimating equation models were used to examine the correlation of allograft histology or BALF microbiology with the presence of BALF eosinophils. Multivariable Cox regression was used to determine the association between ≥ 1% BALF eosinophils in the first posttransplant year and definite CLAD. Expression of eosinophil-relevant genes was quantified in CLAD and transplant control tissues.

RESULTS

The odds of BALF eosinophils being present was significantly higher at the time of acute rejection and nonrejection lung injury histologies and during pulmonary fungal detection. Early posttransplant ≥ 1% BALF eosinophils significantly and independently increased the risk for definite CLAD development (adjusted hazard ratio, 2.04; P = .009). Tissue expression of eotaxins, IL-13-related genes, and the epithelial-derived cytokines IL-33 and thymic stromal lymphoprotein were significantly increased in CLAD.

INTERPRETATION

BALF eosinophilia was an independent predictor of future CLAD risk across a multicenter lung recipient cohort. Additionally, type 2 inflammatory signals were induced in established CLAD. These data underscore the need for mechanistic and clinical studies to clarify the role of type 2 pathway-specific interventions in CLAD prevention or treatment.