Diagnosis of Acute Lung Rejection by Gene Expression Profiling of Bronchoalveolar Lavage Cells

Acute lung rejection is a risk factor for chronic rejection, jeopardizing the long-term survival of lung transplant recipients. At present, acute rejection is diagnosed by transbronchial lung biopsies, which are invasive, expensive, and subject to significant sampling error. In this study, we sought to identify groups of genes whose collective expression in BAL cells best classifies acute rejection versus no-rejection. BAL samples were analyzed from 32 unique subjects whose concurrent histology showed acute rejection (n=14) or no rejection (n=18). Global BAL cell gene expression was measured using Affymetrix U133A microarrays. The nearest shrunken centroid method with 10-fold cross validation was used to define the classification model. 250 runs of the algorithm were performed to determine the range of misclassification error and the most influential genes in determining classifiers. The estimated overall misclassification rate was below 20%. Seven transcripts were present in every classifier and 52 transcripts were present in at least 70% of classifiers; these transcripts were notable for involvement with T-cell function, cytotoxic CD8 activity, and granulocyte degranulation. The proportions of both lymphocytes and neutrophils in BAL samples increased with increasing probability of acute rejection; this trend was more pronounced with neutrophils. We conclude that there is a prominent acute rejection-associated signature in BAL cells characterized by increased T-cell, CD8+ cytotoxic cell, and neutrophil gene expression; this is consistent with established mechanistic concepts of the acute rejection response.

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Patil J, Lande JD, Li N, Berryman TR, King RA, Hertz MI