David J. Ross

Lung allograft dysfunction correlates with γ-interferon gene expression in bronchoalveolar lavage

BACKGROUNDnPreceding episodes of acute cellular rejection (ACR) may predispose lung allografts to the subsequent development of irreversible dysfunction or bronchiolitis obliterans syndrome (BOS). Other histologic patterns such as bronchiolitis obliterans with organizing pneumonia (BOOP), organizing pneumonia, lymphocytic bronchiolitis and diffuse alveolar damage (DAD) may also adversely affect allograft function. We have previously reported the predominant expression of Th1 cytokines (IL-2 and interferon gamma) in rejecting and Th2 (IL-10) in a tolerant model of rat lung transplantation. Here we correlate the Th1/Th2 paradigm in clinical lung transplantation with histologic findings and assess the effect on serial spirometric function.nnnMETHODSnWe examined the mRNA expression of IL-2, interferon gamma, IL-10 and ICAM-1 in 53 bronchoalveolar lavage (BAL) specimens from 23 lung transplant (LT) recipients utilizing qualitative nested reverse transcriptase polymerase chain reaction (RT-PCR). We also measured IgG1 and IgG2 levels in 44 BAL specimens by ELISA. The mRNA expression for cytokines, ICAM-1 and the IgG2/IgG1 ratios were correlated with the presence or absence of ACR and alternate histologic patterns. Serial spirometry were analyzed for the 2-3 month interval before bronchoscopic (FOB) assessment to derive baseline forced expiratory volume-one second (FEV1) values. The change in FEV1 coincident with (deltaFEV1 pre) and for the 2-3 month interval subsequent to (deltaFEV1 post) FOB were expressed relative to baseline spirometric indexes.nnnRESULTSnDetection of mRNA for interferon gamma and ICAM-1 correlated significantly with ACR, whereas IL-2 and IL-10 expression did not correlate. IL-10 was virtually ubiquitous in most BAL samples irrespective of the presence or absence of ACR. The highest correlation was observed with interferon gamma for acute cellular rejection whereupon the sensitivity was 77.7%, specificity 87.7%, positive predictive value 73.6% and negative predictive value 88.2%, although for ICAM-1 these values were 75%, 65.7%, 50.0% and 85.0%, respectively. Nevertheless, 4 of 5 episodes of respiratory tract infection (bacterial, CMV, Aspergillus spp.) were similarly associated with cytokine mRNA. The ratios of IgG2 to IgG1, a reflection of Th1/Th2 influence, were not statistically different when analyzed for the presence or absence of ACR (0.91+/-0.53 vs. 1.02+/-0.70, respectively; p = NS). By analysis of FEV1 trends, expression of interferon gamma was associated with a greater and persistent decrement (deltaFEV1 pre: -0.265+/-0.78 liters, and post: -0.236+/-0.1161; mean +/- SE) than ACR in the absence of interferon gamma expression (+0.158 +/- +0.065 and +0.236+/-0.007 liters, respectively) (Student-Newman-Keuls, p<.05).nnnCONCLUSIONnOur findings suggest that interferon gamma mRNA expression and ICAM-1 may be valuable in both the diagnosis and prognosis for lung allograft ACR. IL-10, a Th2 cytokine, was locally expressed both in the presence and absence of ACR. Expression of mRNA for interferon y in BAL and, to a lesser extent ICAM-1, were associated with increased lung allograft dysfunction. Whether BAL cytokine immunosurveillance would complement or possibly supplant a specific histologic pattern and thereby direct different therapies after lung transplantation, may be potentially rewarding areas of further investigation.

Expression of Γ-IFN mRNA in bronchoalveolar lavage fluid correlates with early acute allograft rejection in lung transplant recipients

Various cytokines are upregulated in acute allograft rejection (AR). Local production of Th‐1 cytokines is suggested to play a pathogenic role in AR, and Th‐2 cytokines in the development of allograft tolerance. The purpose of this study was to correlate the expression of Th‐1 [interleukin‐2 (IL‐2) and Γ‐interferon (Γ‐IFN)], and Th‐2 [interleukin‐10 (IL‐10)] cytokines in bronchoalveolar lavage (BAL) fluid with AR in lung transplant (LT) recipients. The role of Th‐1 dominance expressed as IgG2/IgG1 ratio in BAL in AR was also examined. The mRNA expression for IL‐2, Γ‐IFN and IL‐10 was examined in 64 BAL specimens from 23 LT recipients using reverse transcriptase‐polymerase chain reaction (RT‐PCR). IgG1 and IgG2 levels were measured in 55 BAL specimens by enzyme‐linked immunosorbent assay (ELISA). The expression of mRNA for these cytokines, and the ratio of IgG2/IgG1 was correlated with AR (early AR occurring within 3 months of transplant and late AR occurring after 3 months). Ten patients had 17 episodes of biopsy proven AR. Twelve episodes of AR (6 patients) occurred within the first 3 months of transplantation. In 5 patients, AR was diagnosed 4, 5, 6, 9 and 24 months post‐transplantation. Detection of Γ‐IFN mRNA correlated significantly with early AR (p<0.001), whereas it lacked correlation with late AR. Expression of IL‐2 and IL‐10 mRNA did not correlate with AR. IL‐10 was present in most samples irrespective of the presence or absence of AR. The ratio of IgG2/IgG1 was similar in patients with or without AR. Our findings suggest that the detection of Γ‐IFN mRNA in BAL by RT‐PCR is useful for immune monitoring of early AR in LT recipients. Absence of elevated IgG2/IgG1 ratio, and presence of IL‐10 in BAL during AR suggests that Th‐1 cytokines may not be the sole mediator of rejection in LT recipients.