Immunocytologic analysis of cells obtained from bronchoalveolar lavage in a model of rat lung allograft rejection

Precision monitoring of immunotherapies in solid organ and hematopoietic stem cell transplantation

Pharmacological immunotherapies are a key component of post-transplant therapy in solid-organ and hematopoietic stem cell transplantation. In current clinical practice, immunotherapies largely follow a one-size fits all approach, leaving a large portion of transplant recipients either over- or under-immunosuppressed, and consequently at risk of infections or immune-mediated complications. Our goal here is to review recent and rapid advances in precision and genomic medicine approaches to monitoring of post-transplant immunotherapies. We will discuss recent advances in precision measurements of pharmacological immunosuppression, measurements of the plasma and gut microbiome, strategies to monitor for allograft injury and post-transplant malignancies via circulating cell-free DNA, and comprehensive measurements of the B and T cell immune cell repertoire.

Diagnostic value of plasma and bronchoalveolar lavage samples in acute lung allograft rejection: differential cytology

Diagnosis of acute lung allograft rejection is currently based on transbronchial lung biopsies. Additional methods to detect acute allograft dysfunction derived from plasma and bronchoalveolar lavage samples might facilitate diagnosis and ultimately improve allograft survival. This review article gives an overview of the cell profiles of bronchoalveolar lavage and plasma samples during acute lung allograft rejection. The value of these cells and changes within the pattern of differential cytology to support the diagnosis of acute lung allograft rejection is discussed. Current findings on the topic are highlighted and trends for future research are identified.

Macrophages in experimental rat lung isografts and allografts: infiltration and proliferation in situ

Alveolar macrophages (AMs) and peribronchial/perivascular macrophages are probably involved in lung allograft damage. We investigate leukocyte infiltration into graft tissue and address the question whether proliferation in situ contributes to macrophage homeostasis and accumulation. Lung transplantation was performed in the Lewis (LEW)-to-LEW and in the Dark Agouti-to-LEW rat strain combination. Graft infiltration by ED1+ and ED2+ (CD163) macrophages was analyzed by immunohistochemistry (IHC) and compared with infiltration by lymphocytes. Cells in the S-phase of the cell cycle were pulse-labeled with BrdU and detected immunohistochemically. Finally, the donor or recipient origin of AMs was determined by IHC and in situ hybridization. ED1+ AMs in allogeneic transplants increased by more than 25-fold from Days 1 to 5. In addition, large, peribronchial/perivascular infiltrates developed containing numerous ED1+ cells. Although AMs in normal rat lungs are CD163-, AMs up-regulated CD163 between Days 4 and 5, reaching maximum values on Day 6. Lymphocytes were less numerous than macrophages. About 16% of the AMs and 10% of the peribronchial/perivascular macrophages were in the S-phase of the cell cycle on Day 2 post-transplantation. No differences in the frequency of BrdU+ macrophages were obvious between isografts and allografts. AMs of donor origin increased in number considerably during allograft rejection. In conclusion, the cellular infiltrate in lung allografts is dominated by macrophages, which exhibit an unusual phenotype and a strong capacity for mitotic self-renewal.

Fas/FasL and perforin/granzyme pathway in acute rejection and diffuse alveolar damage after allogeneic lung transplantation?a human biopsy study

Acute rejection and diffuse alveolar damage are major problems during the early time after transplantation. Against this background, lung biopsies after allogeneic lung transplantation were studied using immunohistochemistry. Biopsies with acute rejection, diffuse alveolar damage and morphological inconspicuous biopsies were chosen. The objectives of this study were to ascertain: (a) if and how CD4 and CD8 T cells contribute to allograft rejection and diffuse alveolar damage, (b) whether there is a correlation of the chemoattractant regulated on activation normal T cells (RANTES) with the mononuclear infiltrate and (c) whether perforin/granzyme and Fas/FasL pathways contribute to lung injury after lung transplantation. Our results show that CD4(+) and CD8(+) T cells were increased in biopsies with acute rejection and, to a minor extent, also in biopsies with diffuse alveolar damage due to reperfusion injury. RANTES expression of T cells was increased in biopsies with acute rejection. Perforin seemed to have a dual role in the alloimmune response. In one regard, it had a cytolytic function in the acute rejection process, and, in contrast, it may be responsible for downregulating both CD4- and CD8-mediated alloimmune responses. The FasL/Fas pathway is not only important for induction of apoptosis during rejection but is also a mechanism of lung injury in the development of diffuse alveolar damage.

Interleukin-17 stimulates release of interleukin-8 by human airway smooth muscle cells in vitro: a potential role for interleukin-17 and airway smooth muscle cells in bronchiolitis obliterans syndrome

Bronchiolitis obliterans syndrome is the major constraint on the long-term survival after lung transplantation. Both neutrophils and interleukin (IL)-8, a potent neutrophil attractant, have been shown to play an important role in the pathophysiology of obliterative bronchiolitis. We investigated the potential role of human airway smooth muscle cells in obliterative bronchiolitis by studying their release of IL-8 after stimulation with IL-17, a novel T-cell-derived chemokine capable of attracting and activating neutrophils. We demonstrated a significant increase in IL-8 release, reaching a concentration of 86.6 ng/ml (SEM 1.9 ng/ml) with 100 ng/ml IL-17 (p < 0.01, n = 4), as compared with non-stimulated cells. This IL-17-mediated IL-8 release could not be inhibited by dexamethasone. We conclude that human airway smooth muscle cells may play an important pro-inflammatory role in neutrophilic inflammatory diseases such as chronic rejection after lung transplantation; furthermore, IL-17 may be the link between lymphocytes and neutrophils.

Synergistic effects of CTLA-4Ig and sirolimus on orthotopic lung-allograft survival and histology

BACKGROUND AND AIMS

The combination of CTLA-4Ig with sirolimus can promote indefinite survival in allograft models for which CTLA-4Ig monotherapy is ineffective. We sought to determine whether a limited course of CTLA-4Ig and sirolimus would alter survival of rat orthotopic single-lung transplantations.

METHODS

Left lungs of Brown Norway rats were transplanted into four groups of Lewis recipients (n=6 per group): group 1, no treatment; group 2, mCTLA-4Ig (250 microg/day for 4 days); group 3, sirolimus (3 mg/kg per day for 14 days); group 4, combined therapy with sirolimus and mCTLA-4Ig. Graft survival was determined by daily radiologic examination. Histologic grading of rejection and immunohistochemical staining for T and B lymphocytes were carried out at the time of radiologic graft loss.

RESULTS

Rejection of lung allografts in group 1 occurred at a median of 6.5 days. Neither sirolimus nor mCTLA-4Ig monotherapy resulted in significant prolongation of graft survival (median 9.5 and 8.0 days, respectively). Graft survival in group 4 was significantly prolonged compared with all other groups (median 29.5 days), and a significant reduction in histologic grade of rejection was observed following combination therapy compared with all other groups. Infiltration by CD8+ve T cells at the time of rejection was proportionately greater than CD4+ve T-cell infiltration for groups 1, 2, and 3 but not for the combined-therapy group.

CONCLUSIONS

A brief course of combined mCTLA-4Ig and sirolimus prolongs graft survival, reduces severity of rejection, and attenuates CD8+ve T-cell infiltration of fully major histocompatibility complex mismatched lung allografts.

Eosinophilic infiltrates in a pulmonary allograft: a case and review of the literature

An unusual case of peribronchial eosinophilic infiltrates associated with peripheral blood eosinophilia in a lung transplant patient is described. The role that eosinophils play in lung allograft rejection is reviewed. Tissue eosinophils have been associated with acute pulmonary allograft rejection. Although, eosinophils in bronchoalveolar lavage fluid (BAL) have been observed in allograft rejection, this relationship is less well defined. The role of eosinophils in the pathophysiology of allograft rejection is unclear.

Hydrophobic extracts of a Chinese herb (CMX-13) exhibit potent immunosuppressive properties and prevent acute rejection in a highly histoincompatible model of rat lung transplantation

BACKGROUND

The potential of higher plants as sources for new immunosuppressive medications is well recognized. In our experiments we investigated the immunosuppressive effect of a highly refined and potent extract of a Chinese herbal preparation, CMX-13, on inhibiting acute allograft rejection (AR) in a highly histoincompatible rat lung transplant model, BN-->LEW, and on lymphocyte activation and cytokine gene expression in vitro.

METHODS

Left lung transplants: the control group (group 1) received only dimethylsulfoxide (DMSO) which is the solvent for CMX-13. Group 2 received intramuscular cyclosporin A (CsA, 25 mg/kg) on day 2 posttransplant. Group 3 and 4 received i.p. CMX-13 (0.5 mg/day, low dose and 5 mg/day, high dose, respectively) on day 1, 2, and 3 posttransplant. All animals were killed on day 6 posttransplant. Several pathological categories of inflammation were examined. In vitro experiments: rat spleen cells were incubated with Con A or irradiated stimulator cells with/without serial dilutions of CMX-13 or CsA. Cell proliferation was measured by 3H-thymidine incorporation. mRNA expression of interleukin-2 and interferon-gamma was examined by reverse transcriptase-polymerase chain reaction.

RESULTS

The severity of AR in animals receiving high dose CMX-13 was significantly reduced (stage II, P<0.05) compared with controls (stage IV). Significant differences were also seen when more specific parameters of inflammation were examined (necrosis, 0 vs. 1.7+/-1.0, P<0.05; interalveolar hemorrhage, 0 vs. 3.0+/-0.9, P<0.05). The responses seen in the animals treated with high dose CMX-13 were similar to those in the CsA group. CMX-13 inhibited T cell proliferative responses induced by Con A and alloantigen stimulation in a dose-dependent manner that were similar to CsA. Interleukin-2, and interferon-gamma mRNA expression in Con A-stimulated spleen cells was not inhibited by CMX-13 although CsA showed significant inhibition.

CONCLUSIONS

1) CMX-13 significantly reduces the stage of AR and parameters of inflammation in a highly histoincompatible rat lung transplant model. 2) CMX-13 has equal potency to CsA in the inhibition of Con A and alloantigen stimulated rat spleen cell proliferation. 3) CMX-13 showed no inhibitory effects on IL-2 and gamma-IFN mRNA expression, suggesting that its mechanism of action is different from CsA. 4) CMX-13 or derivatives may have potential utility as an immunosuppressive agent(s) in modulation of AR and management of other inflammatory and immunological disorders.

Bronchoalveolar lavage in lung transplantation. State of the art

Fiberoptic bronchoscopy with bronchoalveolar lavage (BAL) has become a crucial tool in the management of lung transplant recipients. Detection of pulmonary infectious pathogens by culture, cytology, and histology of BAL, protected brush specimens, and transbronchial biopsies (TBB) is highly effective. Morphologic and phenotypological analyses of BAL cells may be suggestive for certain complications after lung transplantation. For interpretation of BAL findings, the natural course of BAL cell morphology and phenotypology after lung transplantation must be considered. During the first 3 months after pulmonary transplantation, elevated total cell count in BAL and neutrophilic alveolitis are common, representing the cellular response to graft injury and interaction of immunocompetent cells of donor and recipient origin. With increasing time after transplantation the CD4/CD8 ratio decreases due to lowered percentages of CD4 cells in BAL. During bacterial pneumonias, the cellular profile of BAL is characterized by a marked granulocytic alveolitis. Lymphocytic alveolitis with a decreased CD4/CD8 ratio is suggestive of acute rejection, but is also found in viral pneumonias and obliterative bronchiolitis. In the case of a combined lymphocytosis and neutrophilia without any evidence of infection, obliterative bronchiolitis should be considered. Functional analyses of BAL cells can give additional information about the immunologic status of the graft, even before histologic changes become evident but have not been established in routine transplant monitoring. However, functional studies suggest an important role of activated, alloreactive and donor-specific T lymphocytes in the pathogenesis of acute and chronic lung rejection. Investigations of soluble components in BAL have given further insight into the immunologic processes after lung transplantation. In this overview, the characteristics of BAL after lung transplantation will be summarized, and its relevance for the detection of pulmonary complications will be discussed.

MIB-1 as a predictor of response in lung allografts with moderate acute cellular rejection

The major obstacle that long-term lung transplant recipients face is bronchiolitis obliterans. Prior episodes of acute rejection, specifically their frequency, persistence, and severity, are important predictors of bronchiolitis obliterans. Many cells contribute to the damage of acute rejection, and there is no sole cell type that can predict persistent rejection or bronchiolitis obliterans. In this study we evaluated 48 transbronchial biopsy samples from various grades of acute rejection with the proliferation marker MIB-1 and attempted to retrospectively predict response to standard corticosteroid in a subpopulation of nine responders and nine nonresponders, all with grade A3 rejection. We then characterized the proliferating cells by double labeling with MIB-1 and L26, CD3, OPD4, or KP1. Our results indicate that the proliferating cells in acute lung rejection are a heterogeneous pool of T- and B-lymphocytes, T-helper cells, macrophages, endothelial cells, and possibly parenchymal cells, and that MIB-1 is a valuable tool in the evaluation of total cellular activity in this setting. In addition, the overall proliferation rate, defined as the most intense proliferation rate regardless of location in the biopsy, closely matches the grade of acute rejection. Finally, a low lesional proliferation rate, defined as the proliferation rate at the site of perivascular inflammation diagnostic of acute rejection, is an indicator of excellent response to therapy and may have potential clinical importance.

Activation of eosinophils in the airways of lung transplantation patients

Eosinophils are important inflammatory cells involved in liver and renal allograft rejection. The role of these cells is less well defined in lung allograft rejection. Eosinophils may be activated in lung rejection and release cytotoxic eosinophil cationic protein (ECP). Other states of disease in lung transplant recipients, such as cytomegalovirus (CMV) and bacterial infection, may also be associated with activated eosinophils. We postulated that ECP may be detectable and elevated in the airway lavage samples obtained from lung transplant patients and may contribute to disease pathogenesis.

METHODS

Fifty BAL samples were collected from 38 lung transplant patients. Their most recent pulmonary function test results within 1 week of collection were noted. The samples were analyzed for the concentration of ECP, WBC count and differential cell count, and total protein level. The results were analyzed to identify the presence of disease or abnormal lung function associated with a positive ECP test. Student's t test was used and a p value of <0.05 was considered significant.

RESULTS

We found that ECP levels were elevated in 36% (n=14) of the patients. Those patients with a positive test result were more likely to have acute rejection, CMV disease, or the presence of a cultured pathogen in BAL compared to patients with a negative test result (p<0.01).

CONCLUSIONS

The presence of BAL ECP is associated with disease in lung transplant patients. Since ECP is directly cytotoxic, it may contribute to disease pathogenesis.

Comparison of lymphocyte subsets, monocytes, and NK cells in three different lung compartments and peripheral blood in the rat

Investigations on leukocyte populations in the lung have shown that lymphocytes are found in different anatomical compartments. Lymphocytes can be seen to a different extent in the lung interstitium, the epithelium and lamina propria of the bronchi, the bronchoalveolar space, and the marginal lung vascular bed. Previous studies focused on one compartment only, or a mixture of leukocytes from lung homogenates were prepared. This study compared cellular yields from the lung parenchyma, the bronchoalveolar space, and the perfusate of the lung vasculature of healthy male Lewis rats. All compartments were investigated in the same animal, and seven different lymphocyte subsets, monocytes, and natural killer (NK) cells were analyzed using flow cytometry. It was found that the perfusate contained a high proportion of CD4+ lymphocytes compared to the lung interstitium. A very high proportion of CD4+ lymphocytes in the bronchoalveolar lavage (BAL) expressed markers for "memory" T cells. Compared to the blood, the percentage of B and T cells was much lower in the perfusate, whereas the NK cells and monocytes were more frequent. Analysis of leukocyte subsets within all compartments revealed specific, distinguishable cell compositions. Extraction of interstitial lung cells was performed using two different methods. Enzymatic digestion of the lung tissue was compared with a mechanical disruption method. Hardly any differences were observed between the two methods regarding the distribution of lymphocyte subsets, monocytes, and NK cells. These data document the need to study more than one compartment before extrapolating to lymphocytes in the lung in general. Furthermore, changes in numbers of leukocytes and subsets can now be studied in models of lung infections and immune reactions, including the entry from the blood and intrapulmonary migration from one lung compartment to the other.

Activation of eosinophils and fibroblasts assessed by eosinophil cationic protein and hyaluronan in BAL. Association with acute rejection in lung transplant recipients

Lung transplantation has become an accepted therapy for end-stage lung disease. Acute rejection of the transplanted hung still remains a major clinical problem since it decreases graft survival. Eosinophil cationic protein (ECP) from activated eosinophils, hyaluronan (HYA) from fibroblasts, and circulating intercellular adhesion molecule 1 (1CAM-1) have been associated with acute rejection in kidney and liver grafts. We investigated whether these, as well as other molecules, were increased in acute rejection of lung allografts. Serum and BAL fluid from 38 bronchoscopies performed in 9 single lung, 2 bilateral lung, and 4 heart-lung transplant patients were studied. Differential cell counts were made from the BAL fluid. Levels of ECP, myeloperoxidase (MPO), and HYA were used as indirect markers for activation of eosinophils, neutrophils, and fibroblasts, respectively. In addition, levels of circulating ICAM-1, cVCAM-1, and cE-selectin were analyzed. Twenty-two episodes with acute rejection were diagnosed. Of these, 7 were minimal, 13 were mild, and 2 were of moderate character. We found increased levels of ECP and HYA in BAL fluid during mild acute rejection of the allograft. Numbers of eosinophils were also increased. Activation of neutrophils or neutrophil numbers were not significantly increased. Levels of circulating ICAM-1, cVCAM-1, and cE-selectin did not differ between the groups. This retrospective study shows that measurements of ECP and HYA can give information about the inflammatory process present during acute rejection in patients who have undergone lung transplants. Analysis of cCAMS, however, appears to be of limited value as markers for acute rejection.