Use of a biotinylated DNA probe specific for the human Y chromosome in the evaluation of the allograft lung

Host CD34+ cells are replacing donor endothelium of transplanted heart

BACKGROUND

Endothelium dysfunction is a central problem for early rejection due to the host alloimmune response and the late status of arteriosclerosis in heart transplantation. However, reliable pieces of evidence are still limited concerning the source of the regenerated endothelium within the transplanted heart.

METHODS

We analyzed single-cell RNA sequencing data and constructed an inducible lineage tracing mouse, combined heart transplantation with bone marrow transplantation and a parabiosis model, cellular components, and endothelial cell populations in cardiac graft lesions.

RESULTS

Our single-cell RNA sequencing analysis of a transplanted heart allowed for the establishment of an endothelial cell atlas with a heterogeneous population, including arterial, venous, capillary, and lymphatic endothelial cells. Along with genetic cell lineage tracing, we demonstrated that the donor cells were mostly replaced by recipient cells in the cardiac allograft, up to 83.29% 2 weeks after transplantation. Furthermore, recipient nonbone marrow CD34+ endothelial progenitors contributed significantly to extracellular matrix organization and immune regulation, with higher apoptotic ability in the transplanted hearts. Mechanistically, peripheral blood-derived human endothelial progenitor cells differentiate into endocardial cells via Vascular endothelial growth factor receptor-mediated pathways. Host circulating CD34+ endothelial progenitors could repair the damaged donor endothelium presumably through CCL3-CCR5 chemotaxis. Partial depletion of host CD34+ cells resulted in delayed endothelial regeneration.

CONCLUSIONS

We created an annotated fate map of endothelial cells in cardiac allografts, indicating how recipient CD34+ cells could replace the donor endothelium via chemokine CCL3-CCR5 interactions. The mechanisms we discovered could have a potential therapeutic effect on the long-term outcomes of heart transplantation.

Methods for studying stem cells: adult stem cells for lung repair

Recent progress in lung biology includes the description of a series of pulmonary stem and progenitor cells involved in homeostasis and regeneration of the respiratory system. Moreover, the contribution of extrapulmonary stem cells to healthy and pathological lung tissue has been observed and the developmental biology of such processes should provide important hints for understanding maintenance and repair of adult lung structure and function. Despite such remarkable advances, the phenotypic and especially the functional characterization of these stem and progenitor cells, and their derivatives, along with an understanding of the molecular cues and pathways underlying differentiation into specific respiratory lineages is still in its infancy. Accordingly, the role of endogenous and extrapulmonary stem cells in normal tissue repair and pathogenesis is still largely mysterious and added basic knowledge is required in order to explore their potential for novel regenerative therapies. This review provides an overview of the current state of the art in adult lung stem cell biology including technical aspects of isolation, characterization and differentiation, and a discussion of perspectives for future regenerative therapies.

Stem Cells and Transplant Arteriosclerosis

Stem cells can differentiate into a variety of cells to replace dead cells or to repair damaged tissues. Recent evidence indicates that stem cells are involved in the pathogenesis of transplant arteriosclerosis, an alloimmune initiated vascular stenosis that often results in transplant organ failure. Although the pathogenesis of transplant arteriosclerosis is not yet fully understood, recent developments in stem cell research have suggested novel mechanisms of vascular remodeling in allografts. For example, stem cells derived from the recipient may repair damaged endothelial cells of arteries in transplant organs. Further evidence suggests that stem cells or endothelial progenitor cells may be released from both bone marrow and non–bone marrow tissues. Vascular stem cells appear to replenish cells that died in donor vessels. Concomitantly, stem/progenitor cells may also accumulate in the intima, where they differentiate into smooth muscle cells. However, several issues concerning the contribution of stem cells to the pathogenesis of transplant arteriosclerosis are controversial, eg, whether bone marrow–derived stem cells can differentiate into smooth muscle cells that form neointimal lesions of the vessel wall. This review summarizes recent research on the role of stem cells in transplant arteriosclerosis, discusses the mechanisms of stem cell homing and differentiation into mature endothelial and smooth muscle cells, and highlights the controversial issues in the field.

New Insights into the Pathogenesis and Treatment of Idiopathic Pulmonary Fibrosis: A Potential Role for Stem Cells in the Lung Parenchyma and Implications for Therapy

Idiopathic Pulmonary Fibrosis (IPF) is a chronic, progressive, and often fatal form of interstitial lung disease. It is characterized by injury with loss of lung epithelial cells and abnormal tissue repair, resulting in replacement of normal functional tissue, abnormal accumulation of fibroblasts and myofibroblasts, deposition of extracellular matrix, and distortion of lung architecture which results in respiratory failure. Despite improvements in the diagnostic approach to IPF and active research in recent years, the molecular mechanisms of the disease remain poorly understood. This highly lethal lung disorder continues to pose major clinical challenges since an effective therapeutic regimen has yet to be identified and developed. For example, a treatment modality has been based on the assumption that IPF is a chronic inflammatory disease, yet most available anti-inflammatory drugs are not effective in treating it. Hence researchers are now focusing on understanding alternative underlying mechanisms involved in the pathogenesis of IPF in the hope of discovering potentially new pharmaceutical targets. This paper will focus on lung tissue repair, regeneration, remodeling, and cell types that may be important to consider in therapeutic interventions and includes a more detailed discussion of the potential targets of current therapeutic attack in pulmonary fibrosis. The discovery that adult bone marrow stem cells can contribute to the formation of differentiated cell types in other tissues, especially after injury, implies that they have the potential to participate in tissue remodeling, and perhaps regeneration. The current promise of the use of adult stem cells for tissue regeneration, and the belief that once irreversibly damaged tissue could be restored to a normal functional capacity using stem cell-based therapy, suggests a novel approach for treatment of diverse chronic diseases. However this optimism is tempered by current evidence that the pathogenesis of pulmonary fibrosis may involve the recruitment of bone marrow-derived fibroblasts, which are the key contributors to the pathogenesis of this chronic progressive disorder. Nevertheless, stem cell-related therapies are widely viewed as promising treatment options for patients suffering from various types of pulmonary diseases. Gender mismatched bone marrow or lung transplant recipients serve as natural populations in which to study the role of bone marrow-derived stem cells in recovery from pulmonary diseases. Understanding the mechanism of recruitment of stem cells to sites of injury, and their involvement in tissue repair, regeneration, and remodeling may offer a novel therapeutic target for developing more effective treatments against this fatal disorder. This article reviews the new concepts in the pathogenesis, current and future treatment options of pulmonary fibrosis, and the recent advances regarding the roles of stem cells in lung tissue repair, regeneration, and remodeling.

The extrapulmonary origin of fibroblasts: stem/progenitor cells and beyond

Although intrapulmonary progenitor cells are traditionally believed to be the source for regenerating cells in response to lung injury, recent mounting evidence indicates that a significant proportion of the mesenchymal cells involved in this repair/remodeling process may be derived from extrapulmonary sources, such as the recently described circulating fibrocyte as well as other bone marrow-derived progenitor cells. Studies tracking CD34 and/or CD45 markers of fibrocytes show their presence in injured murine lung tissue. Moreover, bone marrow chimeric mice with green fluorescence protein (GFP)-expressing marrow cells show abundant GFP-expressing fibroblasts in their lungs in response to lung injury. However, although fibrocytes express CD34 and CD45, and appear to have the capacity to differentiate to myofibroblasts, these properties are not evident in the bone marrow-derived fibroblasts. Induction of CCL21 (SLC) and CXCR12 (SDF1alpha) in injured lung tissue, and their respective cognate receptors, CCR7 and CXCR4, in fibroblasts from injured lungs, suggests recruitment of these extrapulmonary progenitor cells via these chemokines. This is supported by evidence that antibody neutralization of CXCR12 reduces recruitment of fibrocytes and pulmonary fibrosis. In contrast, other studies suggest a protective effect for bone marrow-derived cells. Thus, although suggesting that influx of extrapulmonary fibroblast progenitor cells occurs in response to lung injury, these recent studies do not yet provide clear insight as to the actual phenotype and fate of the recruited cells, the identity of the progenitor cell population in bone marrow, and most important, the function or role of these cells in pathogenesis of the idiopathic interstitial pneumonias.

Bone marrow-derived stem-cell repopulation contributes minimally to the Type II pneumocyte pool in transplanted human lungs

BACKGROUND

Lung transplant recipients are vulnerable to immunologic, infectious, ischemic, and toxic pulmonary injuries. The authors investigated whether type II pneumocytes in the lungs of cross-gender lung transplant patients show genotypic evidence to support repopulation of the lung by stem cells of bone marrow origin, and whether the degree of repopulation was related to rejection history.

METHODS

Recut sections were obtained from lung biopsy specimens from seven male recipients of transplanted lungs from female donors. Sequential immunohistochemistry and fluorescence in situ hybridization was performed on each section to evaluate for Y-chromosome-containing type II pneumocytes.

RESULTS

Y-chromosome-containing type II pneumocytes were found in 9 of 25 biopsy specimens from 5 of 7 gender-mismatched male lung transplant recipients, and accounted for 0% to 0.553% of type II pneumocytes. There was no evidence of polyploidy to suggest cell-cell fusion. The number of type II pneumocytes of male karyotype showed a statistically significant relationship to the cumulative number of episodes of acute cellular rejection.

CONCLUSIONS

Lung transplant recipients develop low levels of pneumocyte repopulation by bone marrow-derived stem cells or their progeny. These cells contribute minimally to the type II pneumocyte proliferation that is often present in these patients as a sequela to alveolar injury.

Role of progenitor cells in transplant arteriosclerosis

To date, chronic transplant dysfunction (CTD) is recognized as the major cause of transplant loss long term after transplantation. CTD has the remarkable histologic feature that the luminal areas of the intragraft arteries become obliterated as a result of occlusive neointima formation. Neointimal lesions contain predominantly vascular smooth muscle cells (VSMCs) and extracellular matrix admixed with inflammatory cells. At the luminal side, neointimal lesions are covered with a monolayer of endothelial cells (ECs). The etiology of transplant arteriosclerosis (TA) is largely unknown, and adequate prevention and treatment protocols are not available. In contrast to the largely accepted "response-to-injury" hypothesis for the development of TA that attributes an important role to graft-derived ECs and VSMCs, recent data indicate that host-derived vascular progenitor cells play a major role in the development of TA. The process leading to TA appears to be heterogeneous, and neointimal ECs and VSMCs can be recruited from different sources, possibly depending on the severity and duration of vascular damage. These data suggest a significant role of host-derived circulating EC/VSMC progenitor cells, which may be partly bone marrow derived. Circulating vascular progenitor cells are potential targets for therapeutic intervention to ameliorate TA development. Therefore, identification of mediators and cellular mechanisms that promote recruitment of vascular progenitors to sites of injury is warranted to dissect their detrimental and possible beneficial effects in the development of TA.

Stem cells of the alveolar epithelium

Elucidation of the biology of stem cells of the lung parenchyma could revolutionise treatment of patients with lung disorders such as cancer, acute respiratory distress syndrome, emphysema, and fibrotic lung disease. How close is this goal? Despite remarkable observations and ensuing advances, more questions than answers have been generated. Progenitors of the alveolar epithelium remain largely mysterious, so the prospect of isolating enough of these cells and delivering them effectively to cure disease remains remote. Similarly, the bone-marrow-derived cell that might most effectively engraft the lung remains unknown. If this mechanism is an important process for lung repair, why will the administration of additional cells be more effective? Finally, there is an issue of control of multipotent cells to avoid the generation of multiple teratomas, longevity of the graft, and possible immunological reactions to gene products inserted to replace a deficiency. The biology is exciting but not yet well enough understood to support therapeutic advances.

Concordance of genotypes in pre- and post-lung transplantation DNA samples

Genetic epidemiology studies of end-stage lung disease are potentially hindered by low numbers of participants due to early death of patients from the underlying disease, or due to exclusion from studies after patients have had lung transplants, because of concern about bias of genotype data due to chimerism. The number of participants enrolled in genetic studies of end-stage lung disease could be increased by including those individuals who have undergone lung transplant. We hypothesized that individuals who have had lung transplants can be included in genetic epidemiology studies that use single nucleotide polymorphism and short tandem repeat marker data, without confounding due to chimerism. Ten probands with severe, early-onset chronic obstructive pulmonary disease were included in this analysis. Pre- and post-lung transplant DNA samples were used in the investigation of concordance of genotype results for 12 short tandem repeat markers and 23 single nucleotide polymorphisms. Concordance was observed for all genotypes before and after lung transplant. We conclude that the risk of biasing genetic epidemiology studies due to donor lung-related DNA microchimerism is low, and that the inclusion of post-lung transplantation participants will allow for larger genetic epidemiology studies of individuals with end-stage lung disease.

Arteriopathy in chronic allograft rejection in liver transplantation

Chronic rejection is an important cause of liver allograft failures. The allograft undergoing chronic rejection shows affected large- and medium-sized muscular arteries with homing of foamy macrophages and enlargement of the intimal area. The objective of this study was to elucidate the pathogenesis of the intimal lesion that causes obliterative arteriopathy by identifying the origin of the foamy macrophages and mesenchymal cells present in the intimal area. Nine allografted livers (6 male and 3 female patients) from sex-mismatched donors undergoing chronic rejection were studied by combined staining of the macrophages or the mesenchymal cells in the intimal area with immunohistochemistry and in situ hybridization using a probe for the human Y chromosome. By using the specimens from female donor allografts transplanted to male recipients, it was found that 62 +/- 11% of CD68+ foamy macrophages and 71 +/- 4% of smooth muscle actin-positive mesenchymal cells in the intimal lesions and a few interstitial myofibroblasts were positive for the Y chromosome probe. This indicated that they were derived from the recipients. In conclusion, the thickening intimal lesion seen in obliterative vasculopathy in liver allografts consists of the foamy macrophages and mesenchymal cells of recipient origin. These circulating recipient cells migrated to the areas in advance of remodeling arteries.

Endothelial replacement and angiogenesis in arteriosclerotic lesions of allografts are contributed by circulating progenitor cells

BACKGROUND

Endothelial regeneration and angiogenesis in the intima of the arterial wall are key events in the pathogenesis of transplantation arteriosclerosis. The traditional hypothesis that damaged endothelial cells are replaced by remaining cells of the donor vessel has been challenged by recent observations, but the cell origins of large arteries and microvessels are still not well established.

METHODS AND RESULTS

Aortic segments were allografted between Balb/c and TIE2-LacZ (C57BL/6) mice expressing beta-galactosidase (gal) in endothelial cells. beta-gal+ cells in TIE2-LacZ vessels grafted to Balb/c mice completely disappeared, whereas the positive cells found in Balb/c aorta allografted into TIE2-LacZ mice 4 weeks after surgery indicated a host origin. En face analysis of allograft vessels displayed a unique distribution of beta-gal+ cells on the surface at 3 days, 1 week, and 4 weeks. Interestingly, 35+/-19% beta-gal+ cells were found in arterial segments allografted into chimeric mice with TIE2-LacZ bone marrows. Furthermore, endothelial cells of microvessels within allografts had a beta-gal+ staining in the media at 1 week and in the neointimal lesions and adventitia at 4 weeks. Allograft studies in chimeric mice demonstrated that beta-gal+ cells of microvessels in transplant arteriosclerosis were derived from bone marrow progenitors.

CONCLUSIONS

We provide strong evidence that endothelial cells of neointimal lesions in allografts are derived from circulating progenitor cells and that bone marrow-derived progenitors are responsible for angiogenesis of the allograft, that is, the formation of microvessels in transplant arteriosclerosis.

Increased chimerism of bronchial and alveolar epithelium in human lung allografts undergoing chronic injury

Chimerism on the parenchymal level has been shown for several human allografts, including liver, heart, and kidney, with the integrated recipient-derived cells most likely originating from multipotent bone marrow precursors. We investigated whether chimerism also occurs within epithelial structures of the lung. For this purpose archival tissue biopsies from seven explanted human lung allografts were obtained. We performed laser microdissection of the target structures with subsequent short tandem repeat analysis to detect chimerism within the isolated cells. We found integration of recipient-derived cells in the bronchial epithelium, in type II pneumocytes and in seromucous glands lying adjacent to larger bronchi in all lung allografts studied. Quantitative analysis revealed that the epithelial structures displaying signs of chronic injury, such as squamous metaplasia, showed a markedly higher degree of chimerism (24% versus 9.5%). We therefore conclude that in human lungs, epithelial chimerism occurs at least within bronchi, type II pneumocytes, and seromucous peribronchial glands. Although a bone marrow origin of immigrating host-derived stem cells has been suggested by previous studies in rodents, analysis of lung biopsies from bone marrow-transplanted patients (n = 3) could not prove such delineation in this study. The observation of an enhanced integration of recipient cells into chronically damaged epithelial structures suggests that extrapulmonary precursor cells are able to contribute to pulmonary regeneration.

Origin of vascular smooth muscle cells and the role of circulating stem cells in transplant arteriosclerosis

To date, clinical solid-organ transplantation has not achieved its goals as a long-term treatment for patients with end-stage organ failure. Development of so-called chronic transplant dysfunction (CTD) is now recognized as the predominant cause of allograft loss long term (after the first postoperative year) after transplantation. CTD has the remarkable histological feature that the luminal areas of intragraft arteries become obliterated, predominantly with vascular smooth muscle cells (VSMCs) intermingled with some inflammatory cells (transplant arteriosclerosis, or TA). The development of TA is a multifactorial process, and many risk factors have been identified. However, the precise pathogenetic mechanisms leading to TA are largely unknown and, as a result, adequate prevention and treatment protocols are still lacking. This review discusses the origin (donor versus recipient, bone marrow versus nonbone marrow) of the VSMCs in TA lesions. Poorly controlled influx and subsequent proliferative behavior of these VSMCs are considered to be critical elements in the development of TA. Available data show heterogeneity when analyzing the origin of neointimal VSMCs in various transplant models and species, indicating the existence of multiple sites of origin. Based on these findings, a model considering plasticity of VSMC origin in TA in relation to severity and extent of graft damage is proposed.

High frequency of epithelial chimerism in liver transplants demonstrated by microdissection and STR-analysis

It has recently been shown that epithelial cells derived from stem cells originating outside the liver are integrated into liver allografts. Whether epithelial intragraft chimerism protects transplants from rejection or chronic transplant dysfunction, and whether it interferes with recurrence of primary liver disease, is not known. Twenty-seven sequential biopsies derived from 9 liver-transplant recipients were studied for chimerism of hepatocytes and cholangiocytes. The target cells were isolated by laser microdissection after cytokeratin immunolabeling and genotyped using DNA analysis of a highly polymorphic short tandem repeat. Irrespective of whether early (up to 4 weeks) or late (more than 12 months) posttransplantation biopsies were studied, cholangiocyte chimerism was almost constantly found in 91% of the samples. No significant differences occurred between samples derived from patients with chronic organ dysfunction (n = 3), recurrent hepatitis (n = 3), or mild, unspecific changes (n = 3). By contrast, hepatocyte chimerism tended to occur later (55% vs. 22%) and appeared to be associated with recurrent hepatitis (67% vs. 27%). In this respect, chronic organ dysfunction did not differ from mild, unspecific changes. While cholangiocyte chimerism represents a constant and early phenomenon in liver transplantations, an enhanced chimeric integration of recipient-derived hepatocytes can be observed in recurrent hepatitis, supporting the concept of an increased recruitment of extrahepatic progenitor cells to the liver in chronic hepatitis.

Origin of neointimal endothelium and alpha-actin-positive smooth muscle cells in transplant arteriosclerosis

The development of transplant arteriosclerosis (TA) is today's most important problem in clinical organ transplantation. Histologically, TA is characterized by perivascular inflammation and progressive intimal thickening. Current thought on this process of vascular remodeling assumes that neointimal vascular smooth muscle (VSM) cells and endothelium in TA are graft-derived, holding that medial VSM cells proliferate and migrate into the subendothelial space in response to signals from inflammatory cells and damaged graft endothelium. Using MHC class I haplotype-specific immunohistochemical staining and single-cell PCR analyses, we show that the neointimal alpha-actin-positive VSM cells in rat aortic or cardiac allografts are of recipient and not of donor origin. In aortic but not in cardiac allografts, recipient-derived endothelial cells (ECs) replaced donor endothelium. Cyclosporine treatment prevents neointima formation and preserves the vascular media in aortic allografts. Recipient-derived ECs do not replace graft endothelium after cyclosporine treatment. We propose that, although it progresses beyond the needs of functional repair, TA reflects the activity of a normal healing process that restores vascular wall function following allograft-induced immunological injury.

Cellular chimerism of the lung after transplantation. An interphase cytogenetic study

The present study evaluated the origin of endothelial and epithelial cells, as well as of lymphocytes and macrophages, after lung transplantation. Biopsy specimens from patients who underwent lung and heart-lung transplantation and received organs of sex-mismatched donors were studied by means of nonisotopic in situ hybridization with DNA probes of the X and Y chromosome. By means of monoclonal antibodies against leukocytes, T and B lymphocytes, and macrophages, the various infiltrating cell types were analyzed. In all allografted lungs, the endothelial cells and bronchial and alveolar epithelium retained the donor sex type. The lymphocytes of the donor were almost completely replaced by recipient cells 1 month after transplantation. Low numbers of alveolar macrophages of the donor were present during the entire period under study. Low numbers of donor lymphocytes and high numbers of donor alveolar macrophages in the allografted lung seem to be correlated with a worse clinical course.

Optimization of non-isotopic in situ hybridization: detection of the Y chromosome in paraformaldehyde-fixed, wax-embedded cat retina

A technique was developed to detect the Y chromosome in paraformaldehyde-fixed diethylglycoldiesterate-embedded cat retina. The Y chromosome specific DNA probe was labeled with digoxigenin through polymerase chain reaction incorporation. After treatment of paraformaldehyde-fixed, diethylglycoldiesterate-embedded tissue sections with deoxyribonucleic acid decondensation and proteolytic digestion, non-fluorescent, non-isotopic in situ hybridization was performed on the retina sections. Most extensive treatment was required for the outer nuclear layer while the inner nuclear layer required more extensive treatment than the retinal pigment epithelial cells. Under optimal pretreatment conditions, the male cat retina displayed black spots which specifically localized at the periphery of the nuclei, while the female cat retina showed negative staining for the Y chromosome specific probe. The technique allows observation of the Y chromosome signal with preservation of retinal morphology and thus may be a valuable tool to discriminate donor cells in retinal pigment epithelial cell and photoreceptor cell transplants.

Posttransplantation physiologic features of the lung and obliterative bronchiolitis

Obliterative bronchiolitis remains the major obstacle to long-term survival after lung transplantation. Herein we provide a brief review of the key literature as well as our own experience with this condition. Obliterative bronchiolitis has occurred in up to two-thirds of all lung transplant recipients. The characteristic physiologic changes include declines in (1) forced expiratory volume in 1 second, (2) forced vital capacity, and (3) diffusing capacity of the lungs for carbon monoxide. Lung biopsy in patients with obliterative bronchiolitis reveals occlusion of bronchioles in a patchy but extensive distribution. Mucous plugging and bronchiectasis may also be seen. Furthermore, intimal thickening of pulmonary vessels together with mild arteriosclerotic changes of the muscular and elastic pulmonary arterioles may be observed. To date, the main risk factor for the development of obliterative bronchiolitis is recurrent, severe, and persistent acute lung rejection. The recommended management is prevention because the established fibrotic condition may necessitate retransplantation.

The association of Epstein-Barr virus with smooth-muscle tumors occurring after organ transplantation

BACKGROUND

Epstein-Barr virus (EBV) has been associated with nasopharyngeal carcinoma, some lymphomas, and lymphoproliferative disease after organ transplantation. Many lymphoproliferative tumors that occur after transplantation are clonal, a property that classifies them as neoplastic. Clonality can be determined by analysis of the extrachromosomal circular DNA episomes produced by EBV infection.

METHODS

We describe three young children in whom smooth-muscle tumors developed 18 months to 5 1/2 years after liver transplantation with immunosuppression. We examined the tumors by microscopy and with immunohistochemical studies and molecular genetic analyses of the EBV DNA:

RESULTS

The tumors were composed of spindle cells with smooth-muscle features and resembled those described in patients with the acquired immunodeficiency syndrome. Immunohistochemical analysis was negative for EBV latent membrane protein and EBV receptor (CD21), but positive for EBV nuclear antigen 2. In situ hybridization revealed nuclear EBV sequences, and molecular genetic analysis showed the EBV genome to be clonal in all three patients.

CONCLUSIONS

Smooth-muscle tumors that developed after organ transplantation contained clonal EBV, suggesting that the virus has a role in the development of these neoplastic lesions.

Lung transplantation

Solid-organ transplantation has flourished during the last decade, with transplantation of heart and lungs becoming available to patients with end-stage cardiac or pulmonary diseases. The first lung transplant was performed in 1963 on a 58-year-old man with bronchogenic carcinoma. He survived for 18 days. During the next two decades, approximately 40 lung transplant procedures were attempted without success. These early attempts at lung transplantation were unsuccessful because of the development of lung rejection, anastomotic complications, or infection in the transplant recipients. In the early 1980s, human heart-lung transplantation was successfully performed for the treatment of pulmonary vascular disease. After this procedure, single-lung transplantation for the treatment of end-stage interstitial lung disease and obstructive lung disease was developed. More recently, the technique of double-lung transplantation has come into existence. This article reviews various aspects of lung transplantation, including immunosuppression, lung graft preservation, the various surgical techniques and types of lung transplant procedures available, recipient and donor selection criteria, and postoperative care of the transplant recipient. In addition, infectious and noninfectious complications seen in this particular patient population, including acute and chronic rejection, will be discussed.