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521: Epithelial Mesenchymal Transition (EMT) in Bronchiolitis Obliterans Syndrome (BOS) Is Not Restricted to Small Airways
S246
Abstracts
The Journal of Heart and Lung Transplantation February 2009
Results: Among the 42 patients (36 male and 6 female), 9.5% received the LVAD as post-cardiotomy bailout operation, 9.5% for destination therapy and 81% as bridge to transplant. Mean age at implantation was 52.1⫾10.5 years. The duration of support ranged from 1 to 368 days (mean 144⫾123 days). Two patients died from septicemia and two from right heart failure, resulting in a 30-daysurvival rate of 90.5%. Up to now, 3 patients have been transplanted and 2 showed recovery of their heart function leading to explantation of the LVAD. Four thromboembolic events occurred during the support period, 2 transitory events with complete recovery after 5 days and two strokes. After 6 months freedom from all thromboembolic cerebral events was 91.4⫾4.8%, and freedom from strokes was 97.3⫾2.7%. Compared to our experience with 266 implantations of continous flow pumps of 6 other types there is a clear tendency toward favourable thromboembolic event rates. Conclusions: With the Thoratec Heart Mate II LVAD we experienced a low rate of cerebral thromboembolic events in our first 42 patients with implantation.
519 Initial Hospitalization Dominates the Mid-Term Costs for Rotary Left Ventricular Assist Devices A.M. Lee1, A. Aziz1, A.K. Leahy2, G. Ridolfi3, I.-W. Wang1, G.A. Ewald4, N. Moazami1 1Washington University, Saint Louis, MO; 2Barnes-Jewish Hospital, Saint Louis, MO; 3Barnes-Jewish Hospital, Saint Louis, MO; 4Washington University, Saint Louis, MO Purpose: Left ventricular assist devices (LVADs) have an increasing role for the treatment of heart failure. Little data have been reported on the costs of the newer generation, rotary devices outside of initial implantation and hospitalization. This study reports six month costs for all rotary LVADs implanted at a single institution over a two year period. Methods and Materials: A retrospective analysis of 22 consecutive patients receiving rotary LVADs (19 Heartmate II, 3 VentrAssist) between 8/31/05 and 12/7/07 was performed. The patients were divided into three groups, patients supported for 6 months (n⫽11), transplanted patients (n⫽5), and patients that did not survive 6 months (n⫽6). Hospital costs were summed starting on the date of implant and included all readmissions and outpatient visits. Cost after transplantation was excluded. One outlier was excluded from analysis. Results: The transplanted group had a mean support of 104 ⫾ 32 days. The non survivor group had a mean support of 69 ⫾ 57 days. Costs are summarized in Table 1. The cost of initial hospitalization accounted for 91%, 97%, and 88% of the overall costs for each group, respectively. Length of stay for the groups were similar, averaging 26 ⫾ 7, 25 ⫾ 12, and 26 ⫾ 25 days (p ⫽ 0.99). Rehospitalization accounted for 88% of subsequent cost overall. The mean number of readmissions and outpatient visits is summarized in Table 2. Conclusions: The majority of the cost of LVAD support arises from the initial hospitalization, even after 6 months of support. Readmissions account for the majority of subsequent costs. Outpatient maintenance of LVAD therapy, proportionally, costs much less. Table 1 Survivors Transplanted Non Survivors
Table 2 Surviors Transplanted Non Survivors
Readmissions
Outpatient Visits
1.3 ⫾ 0.8 1.6 ⫾ 1.0 2.0 ⫾ 0.8
6.0 ⫾ 3.5 2.2 ⫾ 1.2 0
520 Bronchalveolar Lavage Neutrophilia and MMP-9 at 3 Months Post Lung Transplantation May Predict the Development of BOS I. Forrest, C. Ward, D. Murphy, V. Ryan, G. Johnson, J. Lordan, A. Fisher, T. Cawston, P. Corris Newcastle University and Freeman Hospital, Newcastle upon Tyne, United Kingdom Purpose: To investigate if early bronchoalveolar lavage (BAL) neutrophilia and Matrix Metalloproteinase-9 (MMP-9) predicts patients at risk of BOS in a prospective longitudinal study. Methods and Materials: 36 lung allograft recipients (15 male, age 19-61 years) underwent serial bronchoscopy, transbronchial biopsy and standardized BAL (3⫻60ml). A differential cell count was performed on BAL cell pellets and MMP-9 measured in BAL supernatant using a Luminex assay. An ‘upper limit cut-off’ (135 ng/ml) of MMP-9 was determined from a separate population of stable transplant recipients, 3-6months post transplant, with no evidence of acute rejection or infection excluded by technically adequate biopsy and BAL analysis. The MMP-9 / neutrophil % ‘cut-offs’ were determined a priori to survival analysis of freedom from BOS. Analysis was performed using Cox’s proportional hazards model and log rank tests. Results: Median follow-up was 42 months during which time 13 patients developed BOS. Univariate analysis demonstrated that increased BAL neutrophilia of ⬎15% at 3 months increased the rate of developing BOS by 4.4 fold (95% CI 1.2-16.4, p⫽0.02) compared to patients with neutrophils ⬍15%. MMP-9 levels of ⬎135ng/ml at 3 months were associated with a rate ratio of 2.8 in terms of developing BOS compared to patients with lower levels of MMP-9 (95% CI 0.9-9.2, p⫽0.07). Intra-subject and inter-subject correlation of neutophil % and MMP-9 demonstrated a strong positive correlation, r⫽0.49 and 0.60 respectively, p⬍0.001. Conclusions: BAL neutrophilia at 3 months predicts those at risk of developing BOS . Increased levels of MMP-9 are associated with increased BAL neutrophilia and may also predict an increased rate of BOS.
521 Initial Hospitalization
Subsequent Costs
Total Costs
$205323 ⫾ $36663 $194492 ⫾ $46133 $195312 ⫾ $39117
$19302 ⫾ $25117 $ 4145 ⫾ $5515 $19766 ⫾ $41956
$224626 ⫾ $56494 $201238 ⫾ $44650 $222214 ⫾ $74456
Epithelial Mesenchymal Transition (EMT) in Bronchiolitis Obliterans Syndrome (BOS) Is Not Restricted to Small Airways
The Journal of Heart and Lung Transplantation Volume 28, Number 2S
D.C. Chambers1, B. Banerjee5, G. Hodge2, P. Hopkins1, A. Kicic5, M. Musk4, S. Stick5, P. Reynolds2, M. Holmes3, S. Hodge2 1The Prince Charles Hospital, Brisbane, Queensland, Australia; 2 Hanson Institute, Adelaide, South Australia, Australia; 3Royal Adelaide Hospital, Adelaide, South Australia, Australia; 4Royal Perth Hospital, Perth, Western Australia, Australia; 5Telethon Institute for Child Health Research, Perth, Western Australia, Australia Purpose: BOS is predominantly a disease of small airways (SA), although bronchiectasis is a late finding. EMT, characterised by increased epithelial cellular motility (mediated by breakdown of extracellular matrix by metalloproteinases (MMPs)) and the acquisition of a mesenchymal phenotype(␣-smooth muscle actin (␣-sma) and EDA splice variant of fibronectin (EDA⫹FN)), has been implicated in BOS pathogenesis. The purpose of this study was to determine whether EMT is restricted to SA in patients with BOS. Methods and Materials: Flow cytometry (FC) was performed in 16 patients (8 female, aged 24-61, 6 CF, 6 COPD, 4 other, 0.5-129 months post-transplant, 5 BOS) and PCR in another group of 14 (6 female, aged 18-61, 3 CF, 5 UIP, 6 other, 3-121 months post-transplant, 5 BOS). Large airway (LA) and SA (separate brush 2cm from pleural surface) bronchial brushings and bronchoalveolar lavage (BAL) were obtained and assessed for mesenchymal protein (␣-sma, EDA⫹FN, FC) or MMP (PCR /gel zymography) expression. SA lineage was confirmed using clara cell secretory protein. Results: ␣-sma and EDA⫹FN expression were increased in both SA and LA in patients with BOS (Figure). MMP2 and MMP9 were increased 5.1 and 4.9 fold in BAL in patients with BOS (p⬍0.05). MMP2 expression was increased in both SA and LA in BOS (p⫽0.02). Expression of the inhibitor of MMP2, TIMP2, was reduced in both LA and SA compared to healthy controls irrespective of BOS status. MMP9 and TIMP1 epithelial expression were unchanged. Conclusions: Epithelial phenotypic instability consistent with EMT is not restricted to small airways in BOS - the large airways are sick as well. EMT may in part underlie the pathogenesis of the ‘sick airways syndrome’.
522 The Mouse Intrapulmonary Tracheal Transplant Model of Obliterative Bronchiolitis: A Novel Tool To Investigate Lymphoid Neogenesis in the Lung after Transplantation D. Wagnetz, M. Sato, S. Hirayama, J. Yeung, M. Liu, T. Waddell, S. Keshavjee Toronto General Research Institute, University Health Network, Toronto, ON, Canada Purpose: The impact of lymphoid neogenesis in the lung and its relation to obliterative bronchiolitis after lung transplantation is unknown. We herein present a novel model to investigate ectopic de novo lymphoid tissue in the lung.
Abstracts
S247
Methods and Materials: The trachea of Balb/c (allograft) or C57Bl/6 (isograft) mice are implanted into the pulmonary parenchyma of C57Bl/6 mice. The recipient mice were sacrificed at day 14 and day 28 after transplantation (n⫽4/group). Paraffin embedded sections of the left lung were stained for B-cells, T-cells and High Endothelial Venules (HEV), a specialized endothelial cell for homing of naı¨ve lymphocytes to lymphoid tissue. The percentage of obliteration of the tracheal graft was analyzed and the lymphoid areas around the graft were quantified. Results: The intrapulmonary allogenic trachea induced robust formation of lymphoid areas around the graft by day 14 (0.15 ⫾ 0.057 mm2) in contrast to the isogenic trachea (0 ⫾ 0 mm2, p⫽0.004). The lumen of the allograft was significantly obliterated by fibrous tissue (79.95 ⫾ 20.37 %) compared to isografts (0.49 ⫾ 0.31 %, p⫽0.0008); epithelial cells were lost only in allografts. These findings progressed over time with almost complete obliteration of allografts by day 28 (94.61 ⫾ 6.85 %) and enlarging lymphoid areas (0.21 ⫾ 0.02 mm2), whereas the isografts remained open (0.50 ⫾ 0.26 %, p⫽0.00003) with preserved epithelial cells without detectable lymphoid areas. More strikingly, a number of PNAd⫹ HEVs were detected within these lymphoid areas around allografts, confirming the presence of lymphoid structures. This marker was completely absent in isograft transplanted animals. Conclusions: The mouse intrapulmonary tracheal transplant model for the first time clearly demonstrates intrapulmonary lymphoid neogenesis in the setting of allograft airway transplantation. This model will be helpful to further investigate the allograft immune response in the pulmonary environment and the impact of ectopic lymphoid formation. 523 Cells of Epithelial Lineage Are Detectable in Peripheral Blood and Are Increased in Lung Transplantation L.A. May1, A. Kicic2, K. Heel3, B. Banerjee1, M. Musk1, P.M.A. Hopkins4, D.C. Chambers4 1Royal Perth Hospital, Perth, WA, Australia; 2Telethon Institute for Child Health Research, University of Western Australia, Perth, WA, Australia; 3University of Western Australia, Perth, WA, Australia; 4The Prince Charles Hospital, Brisbane, Qld, Australia Purpose: Our previous studies have identified exogenous epithelial cells which have engrafted the transplanted human bronchial epithelium from the circulation. Engrafting cells uniquely expressed the chemokine receptor CXCR4 on the cell surface. We designed this study to attempt to identify cells of a similar phenotype in peripheral blood. Methods and Materials: Ten ml of peripheral blood was collected from healthy controls (n⫽5, aged 23-40, 3 female) and transplant patients (n⫽8, aged 42-62, 3 female, (COPD 4, UIP 1, CF 1, Bronchiectasis 1, CHD 1) 2-66 months post-transplant all BOS 0) and processed immediately. Peripheral blood mononuclear cells (PBMC) were incubated with surface markers (CXCR4-PE; CD45-PerCP and CD14-APC) and then the intracellular epithelial marker pan-KeratinAlexaFluro488 prior to flow cytometry. Monocytes (CD14⫹) were excluded and CD45⫹ and - populations were analysed for epithelial lineage cells. Results: Cells of epithelial lineage were detectable in very low numbers in controls (0.08⫾0.01% of CD14- PBMC), but were 7-fold higher in transplant patients (Figure,*p⬍0.05). Almost all cells expressed CD45 and 79% were CXCR4⫹. The highest number of cells was found in the only patient with residual native lung parenchyma (UIP). Conclusions: For the first time we have identified cells of epithelial lineage in peripheral blood in humans with no history of pregnancy or malignancy. While their differentiative and regenerative potential are under investigation, surface protein expression suggests a bone marrow source and implicates the CXCR4/CXCL12 axis in engraftment of target organs. The dramatic increase in this cellular popula-
Abstracts
The Journal of Heart and Lung Transplantation February 2009
Results: Among the 42 patients (36 male and 6 female), 9.5% received the LVAD as post-cardiotomy bailout operation, 9.5% for destination therapy and 81% as bridge to transplant. Mean age at implantation was 52.1⫾10.5 years. The duration of support ranged from 1 to 368 days (mean 144⫾123 days). Two patients died from septicemia and two from right heart failure, resulting in a 30-daysurvival rate of 90.5%. Up to now, 3 patients have been transplanted and 2 showed recovery of their heart function leading to explantation of the LVAD. Four thromboembolic events occurred during the support period, 2 transitory events with complete recovery after 5 days and two strokes. After 6 months freedom from all thromboembolic cerebral events was 91.4⫾4.8%, and freedom from strokes was 97.3⫾2.7%. Compared to our experience with 266 implantations of continous flow pumps of 6 other types there is a clear tendency toward favourable thromboembolic event rates. Conclusions: With the Thoratec Heart Mate II LVAD we experienced a low rate of cerebral thromboembolic events in our first 42 patients with implantation.
519 Initial Hospitalization Dominates the Mid-Term Costs for Rotary Left Ventricular Assist Devices A.M. Lee1, A. Aziz1, A.K. Leahy2, G. Ridolfi3, I.-W. Wang1, G.A. Ewald4, N. Moazami1 1Washington University, Saint Louis, MO; 2Barnes-Jewish Hospital, Saint Louis, MO; 3Barnes-Jewish Hospital, Saint Louis, MO; 4Washington University, Saint Louis, MO Purpose: Left ventricular assist devices (LVADs) have an increasing role for the treatment of heart failure. Little data have been reported on the costs of the newer generation, rotary devices outside of initial implantation and hospitalization. This study reports six month costs for all rotary LVADs implanted at a single institution over a two year period. Methods and Materials: A retrospective analysis of 22 consecutive patients receiving rotary LVADs (19 Heartmate II, 3 VentrAssist) between 8/31/05 and 12/7/07 was performed. The patients were divided into three groups, patients supported for 6 months (n⫽11), transplanted patients (n⫽5), and patients that did not survive 6 months (n⫽6). Hospital costs were summed starting on the date of implant and included all readmissions and outpatient visits. Cost after transplantation was excluded. One outlier was excluded from analysis. Results: The transplanted group had a mean support of 104 ⫾ 32 days. The non survivor group had a mean support of 69 ⫾ 57 days. Costs are summarized in Table 1. The cost of initial hospitalization accounted for 91%, 97%, and 88% of the overall costs for each group, respectively. Length of stay for the groups were similar, averaging 26 ⫾ 7, 25 ⫾ 12, and 26 ⫾ 25 days (p ⫽ 0.99). Rehospitalization accounted for 88% of subsequent cost overall. The mean number of readmissions and outpatient visits is summarized in Table 2. Conclusions: The majority of the cost of LVAD support arises from the initial hospitalization, even after 6 months of support. Readmissions account for the majority of subsequent costs. Outpatient maintenance of LVAD therapy, proportionally, costs much less. Table 1 Survivors Transplanted Non Survivors
Table 2 Surviors Transplanted Non Survivors
Readmissions
Outpatient Visits
1.3 ⫾ 0.8 1.6 ⫾ 1.0 2.0 ⫾ 0.8
6.0 ⫾ 3.5 2.2 ⫾ 1.2 0
520 Bronchalveolar Lavage Neutrophilia and MMP-9 at 3 Months Post Lung Transplantation May Predict the Development of BOS I. Forrest, C. Ward, D. Murphy, V. Ryan, G. Johnson, J. Lordan, A. Fisher, T. Cawston, P. Corris Newcastle University and Freeman Hospital, Newcastle upon Tyne, United Kingdom Purpose: To investigate if early bronchoalveolar lavage (BAL) neutrophilia and Matrix Metalloproteinase-9 (MMP-9) predicts patients at risk of BOS in a prospective longitudinal study. Methods and Materials: 36 lung allograft recipients (15 male, age 19-61 years) underwent serial bronchoscopy, transbronchial biopsy and standardized BAL (3⫻60ml). A differential cell count was performed on BAL cell pellets and MMP-9 measured in BAL supernatant using a Luminex assay. An ‘upper limit cut-off’ (135 ng/ml) of MMP-9 was determined from a separate population of stable transplant recipients, 3-6months post transplant, with no evidence of acute rejection or infection excluded by technically adequate biopsy and BAL analysis. The MMP-9 / neutrophil % ‘cut-offs’ were determined a priori to survival analysis of freedom from BOS. Analysis was performed using Cox’s proportional hazards model and log rank tests. Results: Median follow-up was 42 months during which time 13 patients developed BOS. Univariate analysis demonstrated that increased BAL neutrophilia of ⬎15% at 3 months increased the rate of developing BOS by 4.4 fold (95% CI 1.2-16.4, p⫽0.02) compared to patients with neutrophils ⬍15%. MMP-9 levels of ⬎135ng/ml at 3 months were associated with a rate ratio of 2.8 in terms of developing BOS compared to patients with lower levels of MMP-9 (95% CI 0.9-9.2, p⫽0.07). Intra-subject and inter-subject correlation of neutophil % and MMP-9 demonstrated a strong positive correlation, r⫽0.49 and 0.60 respectively, p⬍0.001. Conclusions: BAL neutrophilia at 3 months predicts those at risk of developing BOS . Increased levels of MMP-9 are associated with increased BAL neutrophilia and may also predict an increased rate of BOS.
521 Initial Hospitalization
Subsequent Costs
Total Costs
$205323 ⫾ $36663 $194492 ⫾ $46133 $195312 ⫾ $39117
$19302 ⫾ $25117 $ 4145 ⫾ $5515 $19766 ⫾ $41956
$224626 ⫾ $56494 $201238 ⫾ $44650 $222214 ⫾ $74456
Epithelial Mesenchymal Transition (EMT) in Bronchiolitis Obliterans Syndrome (BOS) Is Not Restricted to Small Airways
The Journal of Heart and Lung Transplantation Volume 28, Number 2S
D.C. Chambers1, B. Banerjee5, G. Hodge2, P. Hopkins1, A. Kicic5, M. Musk4, S. Stick5, P. Reynolds2, M. Holmes3, S. Hodge2 1The Prince Charles Hospital, Brisbane, Queensland, Australia; 2 Hanson Institute, Adelaide, South Australia, Australia; 3Royal Adelaide Hospital, Adelaide, South Australia, Australia; 4Royal Perth Hospital, Perth, Western Australia, Australia; 5Telethon Institute for Child Health Research, Perth, Western Australia, Australia Purpose: BOS is predominantly a disease of small airways (SA), although bronchiectasis is a late finding. EMT, characterised by increased epithelial cellular motility (mediated by breakdown of extracellular matrix by metalloproteinases (MMPs)) and the acquisition of a mesenchymal phenotype(␣-smooth muscle actin (␣-sma) and EDA splice variant of fibronectin (EDA⫹FN)), has been implicated in BOS pathogenesis. The purpose of this study was to determine whether EMT is restricted to SA in patients with BOS. Methods and Materials: Flow cytometry (FC) was performed in 16 patients (8 female, aged 24-61, 6 CF, 6 COPD, 4 other, 0.5-129 months post-transplant, 5 BOS) and PCR in another group of 14 (6 female, aged 18-61, 3 CF, 5 UIP, 6 other, 3-121 months post-transplant, 5 BOS). Large airway (LA) and SA (separate brush 2cm from pleural surface) bronchial brushings and bronchoalveolar lavage (BAL) were obtained and assessed for mesenchymal protein (␣-sma, EDA⫹FN, FC) or MMP (PCR /gel zymography) expression. SA lineage was confirmed using clara cell secretory protein. Results: ␣-sma and EDA⫹FN expression were increased in both SA and LA in patients with BOS (Figure). MMP2 and MMP9 were increased 5.1 and 4.9 fold in BAL in patients with BOS (p⬍0.05). MMP2 expression was increased in both SA and LA in BOS (p⫽0.02). Expression of the inhibitor of MMP2, TIMP2, was reduced in both LA and SA compared to healthy controls irrespective of BOS status. MMP9 and TIMP1 epithelial expression were unchanged. Conclusions: Epithelial phenotypic instability consistent with EMT is not restricted to small airways in BOS - the large airways are sick as well. EMT may in part underlie the pathogenesis of the ‘sick airways syndrome’.
522 The Mouse Intrapulmonary Tracheal Transplant Model of Obliterative Bronchiolitis: A Novel Tool To Investigate Lymphoid Neogenesis in the Lung after Transplantation D. Wagnetz, M. Sato, S. Hirayama, J. Yeung, M. Liu, T. Waddell, S. Keshavjee Toronto General Research Institute, University Health Network, Toronto, ON, Canada Purpose: The impact of lymphoid neogenesis in the lung and its relation to obliterative bronchiolitis after lung transplantation is unknown. We herein present a novel model to investigate ectopic de novo lymphoid tissue in the lung.
Abstracts
S247
Methods and Materials: The trachea of Balb/c (allograft) or C57Bl/6 (isograft) mice are implanted into the pulmonary parenchyma of C57Bl/6 mice. The recipient mice were sacrificed at day 14 and day 28 after transplantation (n⫽4/group). Paraffin embedded sections of the left lung were stained for B-cells, T-cells and High Endothelial Venules (HEV), a specialized endothelial cell for homing of naı¨ve lymphocytes to lymphoid tissue. The percentage of obliteration of the tracheal graft was analyzed and the lymphoid areas around the graft were quantified. Results: The intrapulmonary allogenic trachea induced robust formation of lymphoid areas around the graft by day 14 (0.15 ⫾ 0.057 mm2) in contrast to the isogenic trachea (0 ⫾ 0 mm2, p⫽0.004). The lumen of the allograft was significantly obliterated by fibrous tissue (79.95 ⫾ 20.37 %) compared to isografts (0.49 ⫾ 0.31 %, p⫽0.0008); epithelial cells were lost only in allografts. These findings progressed over time with almost complete obliteration of allografts by day 28 (94.61 ⫾ 6.85 %) and enlarging lymphoid areas (0.21 ⫾ 0.02 mm2), whereas the isografts remained open (0.50 ⫾ 0.26 %, p⫽0.00003) with preserved epithelial cells without detectable lymphoid areas. More strikingly, a number of PNAd⫹ HEVs were detected within these lymphoid areas around allografts, confirming the presence of lymphoid structures. This marker was completely absent in isograft transplanted animals. Conclusions: The mouse intrapulmonary tracheal transplant model for the first time clearly demonstrates intrapulmonary lymphoid neogenesis in the setting of allograft airway transplantation. This model will be helpful to further investigate the allograft immune response in the pulmonary environment and the impact of ectopic lymphoid formation. 523 Cells of Epithelial Lineage Are Detectable in Peripheral Blood and Are Increased in Lung Transplantation L.A. May1, A. Kicic2, K. Heel3, B. Banerjee1, M. Musk1, P.M.A. Hopkins4, D.C. Chambers4 1Royal Perth Hospital, Perth, WA, Australia; 2Telethon Institute for Child Health Research, University of Western Australia, Perth, WA, Australia; 3University of Western Australia, Perth, WA, Australia; 4The Prince Charles Hospital, Brisbane, Qld, Australia Purpose: Our previous studies have identified exogenous epithelial cells which have engrafted the transplanted human bronchial epithelium from the circulation. Engrafting cells uniquely expressed the chemokine receptor CXCR4 on the cell surface. We designed this study to attempt to identify cells of a similar phenotype in peripheral blood. Methods and Materials: Ten ml of peripheral blood was collected from healthy controls (n⫽5, aged 23-40, 3 female) and transplant patients (n⫽8, aged 42-62, 3 female, (COPD 4, UIP 1, CF 1, Bronchiectasis 1, CHD 1) 2-66 months post-transplant all BOS 0) and processed immediately. Peripheral blood mononuclear cells (PBMC) were incubated with surface markers (CXCR4-PE; CD45-PerCP and CD14-APC) and then the intracellular epithelial marker pan-KeratinAlexaFluro488 prior to flow cytometry. Monocytes (CD14⫹) were excluded and CD45⫹ and - populations were analysed for epithelial lineage cells. Results: Cells of epithelial lineage were detectable in very low numbers in controls (0.08⫾0.01% of CD14- PBMC), but were 7-fold higher in transplant patients (Figure,*p⬍0.05). Almost all cells expressed CD45 and 79% were CXCR4⫹. The highest number of cells was found in the only patient with residual native lung parenchyma (UIP). Conclusions: For the first time we have identified cells of epithelial lineage in peripheral blood in humans with no history of pregnancy or malignancy. While their differentiative and regenerative potential are under investigation, surface protein expression suggests a bone marrow source and implicates the CXCR4/CXCL12 axis in engraftment of target organs. The dramatic increase in this cellular popula-