Immunosuppression, eotaxin and the diagnostic changes in eosinophils that precede early acute heart allograft rejection

Time-dependent blood eosinophilia count increases the risk of kidney allograft rejection

Background

Growing evidence suggest that type 2 immune effectors play a role in solid organ transplantation. The aim of this study was to evaluate the impact of blood count eosinophils (BCEo) on immunological outcomes in kidney transplant recipients with stable graft function after 3 months post-transplant.

Method

We performed cause-specific Cox model considering BCEo, the use of calcineurin inhibitors and systemic corticoids as time-dependent explicative variables on a prospective cohort of 1013 kidney transplant patients who experienced kidney allograft rejection and/or the appearance of de novo donor specific antibodies after excluding common causes of increased BCEo..

Findings

BCEo ≥ 0.3 G/L was associated with a 3-fold increased risk of rejection independent of immunosuppressive regimen after 3 months post-transplant in patients without pre-transplant DSAs and with CNI-based immunosuppression. No association between BCEo either with donor specific antibodies or graft survival was noticed.

Interpretation

These observations in this large cohort support the hypothesis of eosinophils in allo-immunity in human and claim for further mechanistic research.

Funding

This study was supported by the French National Research Agency, The “Institut de Recherche en Santé Respiratoire des Pays de la Loire” and the University hospital of Nantes.

The Eosinophil in Health and Disease: from Bench to Bedside and Back

Historically, eosinophils have been considered as end-stage cells involved in host protection against parasitic infection and in the mechanisms of hypersensitivity. However, later studies have shown that this multifunctional cell is also capable of producing immunoregulatory cytokines and soluble mediators and is involved in tissue homeostasis and modulation of innate and adaptive immune responses. In this review, we summarize the biology of eosinophils, including the function and molecular mechanisms of their granule proteins, cell surface markers, mediators, and pathways, and present comprehensive reviews of research updates on the genetics and epigenetics of eosinophils. We describe recent advances in the development of epigenetics of eosinophil-related diseases, especially in asthma. Likewise, recent studies have provided us with a more complete appreciation of how eosinophils contribute to the pathogenesis of various diseases, including hypereosinophilic syndrome (HES). Over the past decades, the definition and criteria of HES have been evolving with the progress of our understanding of the disease and some aspects of this disease still remain controversial. We also review recent updates on the genetic and molecular mechanisms of HES, which have spurred dramatic developments in the clinical strategies of diagnosis and treatment for this heterogeneous group of diseases. The conclusion from this review is that the biology of eosinophils provides significant insights as to their roles in health and disease and, furthermore, demonstrates that a better understanding of eosinophil will accelerate the development of new therapeutic strategies for patients.

Activation of eosinophil CCR3 signaling and eotaxin using a bioinformatics analysis of a mouse model of obliterative airway disease

The role of eosinophils in the development and progression of chronic allograft rejection is recognized in multiple organ transplantation settings. The CCR3 signaling pathway is one of the key regulatory pathways in eosinophil migration to the engrafted tissue. Eotaxin is a ligand for CCR3 and reflects eosinophilic inflammation, which can lead to fibrosis. We hypothesized that the CCR3 pathway would be upregulated in obliterative airway disease (OAD) in an established model of chronic airway allograft rejection. The mouse gene microarray data from a heterotopic mouse model of OAD in the NIH Gene Expression Omnibus (GEO) repository were analyzed for differentially expressed eosinophil pathways, using the Partek Suite and Ingenuity Pathway Analysis. A P value of <0.005 was defined as significant for differential expression, and P value of <0.05 for pathways. Day 25 allografts were defined as chronic allograft rejection and day 4 as acute allograft rejection. The isografts and allografts at day 25 showed significant upregulation of the eosinophil CCR3 pathway (P=0.04), based on the analysis of 1,299 uniquely expressed genes. The isografts at day 4 were compared with those at day 25 based on the identification of 1,859 unique genes, and there was a trend toward the CCR3 pathway upregulation over time (P=0.06). CCR3 pathways were not upregulated during the progression of alloimmune rejection in the allografts at day 4 versus day 25 in comparison, based on the analysis of 1,603 genes. Eotaxin was upregulated in chronic allograft rejection by 2.5-fold. The eosinophil signaling pathway CCR3 and eotaxin were significantly expressed in chronic allograft rejection and our results imply a role in controlling early alloimmune damage in controls.

The expanding role(s) of eosinophils in health and disease

Surprisingly, the role(s) of eosinophils in health and disease is often summarized by clinicians and basic research scientists as a pervasive consensus opinion first learned in medical/graduate school. Eosinophils are rare white blood cells whose activities are primarily destructive and are only relevant in parasitic infections and asthma. However, is this consensus correct? This review argues that the wealth of available studies investigating the role(s) of eosinophils in both health and disease demonstrates that the activities of these granulocytes are far more expansive and complex than previously appreciated. In turn, this greater understanding has led to the realization that eosinophils have significant contributory roles in a wide range of diseases. Furthermore, published studies even implicate eosinophil-mediated activities in otherwise healthy persons. We suggest that the collective reports in the literature showing a role for eosinophils in an ever-increasing number of novel settings highlight the true complexity and importance of this granulocyte. Indeed, discussions of eosinophils are no longer simple and more often than not now begin with the question/statement "Did you know …?"