Solving the Conundrum of Eosinophils in Alloimmunity

Stress-induced eosinophil activation contributes to postoperative morbidity and mortality after lung resection

Respiratory failure occurs more frequently after thoracic surgery than abdominal surgery. Although the etiology for this complication is frequently attributed to underlying lung disease present in patients undergoing thoracic surgery, this notion is often unfounded because many patients with normal preoperative pulmonary function often require prolonged oxygen supplementation even after minimal resection of lung tissue. Using a murine model of pulmonary resection and peripheral blood samples from patients undergoing resection of the lung or abdominal organs, we demonstrated that lung surgery initiates a proinflammatory loop that results in damage to the remaining lung tissue, noncardiogenic pulmonary edema, hypoxia, and even death. Specifically, we demonstrated that resection of murine lung tissue increased concentrations of the homeostatic cytokine interleukin-7, which led to local and systemic activation of type 2 innate lymphoid cells. This process activated lung-resident eosinophils and facilitated stress-induced eosinophil maturation in the bone marrow in a granulocyte-macrophage colony-stimulating factor-dependent manner, resulting in systemic eosinophilia in both mice and humans. Up-regulation of inducible nitric oxide synthase in lung-resident eosinophils led to tissue nitrosylation, pulmonary edema, hypoxia, and, at times, death. Disrupting this activation cascade at any stage ameliorated deleterious outcomes and improved survival after lung resection in the mouse model. Our data suggest that repurposing US Food and Drug Administration-approved eosinophil-targeting strategies may potentially offer a therapeutic intervention to improve outcomes for patients who require lung resection for benign or malignant etiology.

Exploration of the shared gene signatures and biological mechanisms between ischemia-reperfusion injury and antibody-mediated rejection in renal transplantation

BACKGROUND

Antibody-mediated rejection (ABMR) plays a crucial role in graft loss during allogeneic renal transplantation. In renal transplantation, ischemia-reperfusion injury (IRI) is unavoidable, serves as a major contributor to acute rejection, and is linked to graft loss. However, the mechanisms underlying IRI and ABMR are unclear. Therefore, this study aimed to investigate the shared genetic characteristics and biological mechanisms between IRI and ABMR.

METHODS

Gene expressions for IRI (GSE43974) and ABMR (GSE129166 and GSE36059) were retrieved from the Gene Expression Omnibus database. The shared differentially expressed genes (DEGs) of IRI and ABMR were identified, and subsequent functional enrichment analysis was performed. Immune cell infiltration in ABMR and its relationship with the shared DEGs were investigated using the CIBERSORT method. Random forest analysis, a protein-protein interaction network, and Cytoscape were used to screen hub genes, which were subsequently subjected to gene set enrichment analysis, miRNA prediction, and transcription factors analysis. The survival analysis was performed through Kaplan-Meier curves. Finally, drug compound prediction was performed on the shared DEGs using the Drug Signature Database.

RESULTS

Overall, 27 shared DEGs were identified between the renal IRI and ABMR groups. Among these, 24 genes exhibited increased co-expression, whereas none showed decreased co-expression. The shared DEGs were primarily enriched in the inflammation signaling pathways. Notably, CD4 memory T cells were identified as potential critical mediators of IRI, leading to ABMR. Tumor necrosis factor alpha-induced protein 3 (TNFAIP3), interferon regulatory factor 1 (IRF1), and early growth response 2 (EGR2) were identified as key components in the potential mechanism that link IRI and ABMR. Patients undergoing renal transplantation with higher expression levels of TNFAIP3, IRF1, and EGR2 exhibited decreased survival rates compared to those with lower expression levels.

CONCLUSION

Inflammation is a key mechanism that links IRI and ABMR, with a potential role played by CD4 memory T cells. Furthermore, TNFAIP3, IRF1, and EGR2 are implicated in the underlying mechanism between IRI and ABMR.

Eosinophilic infiltration as the initial trace of acute mixed cellular and antibody mediated rejection in a heart transplant patient with concomitant immense epitope-associated HLA-antibody production: a case report

Acute mixed cellular and antibody-mediated rejection (MR) has an estimated prevalence of 7.8%. However, knowledge of MR immune pathogenesis in cardiac graft rejection remains sparse. We report a case of acute MR in a heart transplant patient with a mutation in the MYH7 gene encoding the protein β-myosin heavy chain, resulting in familial hypertrophic cardiomyopathy. The patient presented with substantial eosinophilic infiltration and extensive production of Human Leukocyte Antigen (HLA)-antibodies associated with shared epitopes. Eosinophilic infiltration in the endo- and myocardium was diagnosed in routine post-transplant biopsies stained with hematoxylin-eosin on day 6 after transplantation. On day 27, the patient presented with dyspnea, weight gain, increased pro-brain natriuretic peptide, and was hospitalized due to suspected acute rejection. Endomyocardial biopsies showed eosinophils in endo- and myocardium with additional lymphocytes and hyperplastic endothelium. Immunohistochemistry, including CD31/CD68 double stain confirmed endothelium-associated macrophages in capillaries and severe C4d positivity in the capillaries and endocardial endothelium. Lymphocytes were identified as primarily CD45+/CD3+ T cells with a concomitant few CD45+/CD20+ B cells. HLA-antibody analysis demonstrated a significant increase in 13 HLA-antibodies present in pre-transplant-serum, of which anti-B7 was donor-specific, and 23 strong de-novo HLA-class I antibodies of which anti-B62 was donor-specific. 72% of HLA-antibodies, including the two donor-specific antibodies, shared the same HLA antigen epitope; 43P+69A or 163L+167W. This is a case reporting both HLA-antibody and pathohistological data indicating the need for better understanding of interactions between cellular and antibody-mediated immune response mechanisms in graft rejection, and the significance of pre-transplant donor-specific antibodies during immunological pre-transplant risk assessment.