BRONCHIOALVEOLAR LAVAGE AND SERUM INDICATORS OF LUNG TRANSPLANT OUTCOME

Abstract

63 Background: Despite a steady increase in lung allograft survival, Bronchiolitis Obliterans Syndrome (BOS) and acute rejection remain major complications, resulting in almost 50% graft loss by 5 years post transplant. Determination of which allografts will recover from acute rejection episodes or proceed to graft loss or BOS is difficult. Hypothesis: Early events will alter the balance of allograft acceptance or rejection and these can be determined by release of activation-dependent β2m-free HLA heavy chain (HC) and total HLA (sHLA/β2m) into the bronchioalveolar lavage (BAL), the release of donor-derived sHLA/β2m into the serum, and the rapid depletion of donor chimeric cells from the epithelial lining fluid sampled by the BAL. Methods: We analyzed lung allografts in 38 patients (21 bilateral, 19 single, 2 retransplants) for up to 1600 days post transplant. Routinely sampled BAL was analyzed for β2m-free HC and sHLA/β2m from all allografts using an ELISA. We were able to determine the percent of donor chimeric cells in BAL from 21 of the patients with 2 color FACS analysis and antibodies for donor and or recipient HLA class I or class II antigens. Using a specific ELISA, we determined the concentration of donor-derived sHLA/β2m in the serum from 13 of the patients. Results: We found that early events (<200 days post transplant) were strong indicators of graft outcome. In patients with good graft outcome (no rejection graft loss or development of BOS, n=21) there were low levels of β2m-free HC and sHLA/β2m and an average of ≥ 2% persistent donor leukocytes in the BAL as well as low levels of donor-derived sHLA/β2m in the serum (p=0.004, 0.02, 0.0017 and 0.001 respectively vs patients with poor outcome). In contrast, all 8 grafts which were lost to refractory acute rejection had either high β2m-free HC, sHLA/β2m or both in the BAL and none had an average of ≥ 2% donor cells in the BAL (n=4). Excluding those with acute rejection graft loss, the concentration of β2m-free HC was significantly correlated with the development of BOS (p=0.003) as was the % of donor cells in the BAL (p=0.028), whereas the concentration of sHLA/β2m was not (p=0.27). The average concentration of β2m-free HC in the first 200 days was also correlated with the time to poor function and particularly time to development of BOS (P=0.009). Conclusions: The rapid loss of donor cells and the release of donor sHLA into the periphery and sHLA/β2m are indicators of activation directed against the allograft and are predictors of poor graft outcome. The release of β2m-free HC may be an indicator of subtle activation events which are currently undetected by conventional methods but may be important for the development of BOS. This work was supported by a grant from the University of Wisconsin Surgical Associates.