Donor Macrophages Modulate Rejection After Heart Transplantation.

BACKGROUND: Cellular rejection after heart transplantation imparts significant morbidity and mortality. Current immunosuppressive strategies are imperfect, target recipient T cells, and have adverse effects. The innate immune response plays an essential role in the recruitment and activation of T cells. Targeting the donor innate immune response would represent the earliest interventional opportunity within the immune response cascade. There is limited knowledge about donor immune cell types and functions in the setting of cardiac transplantation, and no current therapeutics exist for targeting these cell populations. METHODS: Using genetic lineage tracing, cell ablation, and conditional gene deletion, we examined donor mononuclear phagocyte diversity and macrophage function during acute cellular rejection of transplanted hearts in mice. We performed single-cell RNA sequencing on donor and recipient macrophages and monocytes at multiple time points after transplantation. On the basis of our imaging and single-cell RNA sequencing data, we evaluated the functional relevance of donor CCR2+ (C-C chemokine receptor 2) and CCR2- macrophages using selective cell ablation strategies in donor grafts before transplant. Last, we performed functional validation that donor macrophages signal through MYD88 (myeloid differentiation primary response protein 88) to facilitate cellular rejection. RESULTS: Donor macrophages persisted in the rejecting transplanted heart and coexisted with recipient monocyte-derived macrophages. Single-cell RNA sequencing identified donor CCR2+ and CCR2- macrophage populations and revealed remarkable diversity among recipient monocytes, macrophages, and dendritic cells. Temporal analysis demonstrated that donor CCR2+ and CCR2- macrophages were transcriptionally distinct, underwent significant morphologic changes, and displayed unique activation signatures after transplantation. Although selective depletion of donor CCR2- macrophages reduced allograft survival, depletion of donor CCR2+ macrophages prolonged allograft survival. Pathway analysis revealed that donor CCR2+ macrophages are activated through MYD88/nuclear factor kappa light chain enhancer of activated B cells signaling. Deletion of MYD88 in donor macrophages resulted in reduced antigen-presenting cell recruitment, reduced ability of antigen-presenting cells to present antigen to T cells, decreased emergence of allograft-reactive T cells, and extended allograft survival. CONCLUSIONS: Distinct populations of donor and recipient macrophages coexist within the transplanted heart. Donor CCR2+ macrophages are key mediators of allograft rejection, and deletion of MYD88 signaling in donor macrophages is sufficient to suppress rejection and extend allograft survival. This highlights the therapeutic potential of donor heart-based interventions.

Clinical factors and high-resolution manometry predicting response to surgery for achalasia in children.

BACKGROUND: Esophageal achalasia is an uncommon condition in children. Although many interventions exist for the management of this disorder, esophageal (Heller) myotomy offers one of the most durable treatments. Our institution sought to review patients undergoing Heller myotomy concentrating on preoperative clinical factors that might predict postoperative outcomes. MATERIALS AND METHODS: All patients from January 1, 2007, to December 31, 2016, who underwent surgical treatment for achalasia at our tertiary pediatric hospital were identified and included in the study cohort. Electronic medical records for these patients were reviewed for clinical presentation variables, nonsurgical preoperative treatment, surgical approach, clinical response to surgery, need for postoperative treatment for ongoing symptoms, and high-resolution manometry (HRM) data. RESULTS: Twenty-six patients were included in the study, and all underwent myotomy with partial fundoplication (median age: 14.4 y [interquartile range 11.6-15.5]). At a median follow-up of 9.75 mo (interquartile range 3.5-21 mo), 16 (61.5%) patients reported good resolution of their dysphagia symptoms with surgery alone. Two patients (7.7%) had perforation of the gastrointestinal tract requiring surgical intervention. Eight patients (30.8%) required additional treatment for achalasia, with 5 (19.2%) of these undergoing additional surgery or endoscopic treatment. Patients who had preoperative dilation did not have good resolution of their dysphagia (n = 2; P = 0.037). Two of four patients undergoing postoperative dilation had preoperative dilation. None of these patients underwent preoperative manometry. There was a statistically significant difference in the ages of patients who required postoperative intervention and those who did not (14.1 versus 15.2 y old, respectively; P = 0.043). In patients who reported improvement of gastroesophageal reflux disease/reflux type symptoms after Heller myotomy, lower esophageal residual pressure (29.1 versus 18.7 mmHg; P = 0.018) on preoperative HRM was significantly higher than in those who did not report improvement after surgery. Higher upper esophageal mean pressure (66.6 versus 47.8 mmHg; P = 0.05) also predicted good gastroesophageal reflux disease/reflux symptom response in a similar manner. CONCLUSIONS: Current analysis suggests that preoperative dilation should be used cautiously and older patients may have a better response to surgery without need for postoperative treatment. In addition, preoperative HRM can aid in counseling patients in the risk of ongoing symptoms after surgery and may aid in determining if a fundoplication should be completed at the index procedure. Further research is needed to delineate these factors. LEVEL OF EVIDENCE: Level III.

Lymphatic drainage from bronchus-associated lymphoid tissue in tolerant lung allografts promotes peripheral tolerance.

Tertiary lymphoid organs are aggregates of immune and stromal cells including high endothelial venules and lymphatic vessels that resemble secondary lymphoid organs and can be induced at nonlymphoid sites during inflammation. The function of lymphatic vessels within tertiary lymphoid organs remains poorly understood. During lung transplant tolerance, Foxp3+ cells accumulate in tertiary lymphoid organs that are induced within the pulmonary grafts and are critical for the local downregulation of alloimmune responses. Here, we showed that tolerant lung allografts could induce and maintain tolerance of heterotopic donor-matched hearts through pathways that were dependent on the continued presence of the transplanted lung. Using lung retransplantation, we showed that Foxp3+ cells egressed from tolerant lung allografts via lymphatics and were recruited into donor-matched heart allografts. Indeed, survival of the heart allografts was dependent on lymphatic drainage from the tolerant lung allograft to the periphery. Thus, our work indicates that cellular trafficking from tertiary lymphoid organs regulates immune responses in the periphery. We propose that these findings have important implications for a variety of disease processes that are associated with the induction of tertiary lymphoid organs.