Abstract Rationale Primary graft dysfunction (PGD) in lung transplant recipients (LTRs) is associated with poor short-term outcomes; however, its impact on long-term allograft dysfunction is less clear. Previous findings demonstrated an immune activation gene expression signature in airway brushes for chronic lung allograft dysfunction. We sought to evaluate whether gene expression associated with PGD demonstrated similar immune activation over time. Methods This was a multicenter, prospective study conducted at three centers as part of the NHLBI LTC. Airway brushes were obtained from consented LTRs at 1, 6, and 12 months post-transplant. Patients were grouped by maximum PGD grade 0-1 versus 3. Acute cellular rejection (ACR) was assessed in the first 6 months and FEV1 values were trended over the first-year post-transplant. Bulk RNAseq raw reads were aligned to the human reference genome (GRCh38) to generate gene-level count matrices. Normalization and differential gene expression analysis were conducted using the DESeq2. Differentially expressed genes (DEGs) were defined by an absolute log2 fold change 1.5 and an adjusted p-value 0.05. Pathway enrichment analysis was performed using KEGG. Results 136 airway brushes from 46 LTRs (26 maximum PGD grade 0-1 vs 20 grade 3) were analyzed. There was no difference in the slope of the FEV1 trend in the first-year post-transplant (0.043 vs 0.054 L/month, p = 0.615) or the 6-month rate of ACR (27% vs 30%, p = 0.82) between PGD groups. RNAseq revealed major DEGs at the 1-month timepoint: 1,200 DEGs were detected, with strong enrichment of immune and inflammatory pathways—particularly cytokine, TNF, and IL-17 signaling. Pro-inflammatory chemokines (CCL3, CXCL2/3, CXCL10) were upregulated, but anti-inflammatory mediators (TGF-beta, SOCS3, IL-10RB) were also increased, suggesting early activation of both pro- and counter-regulatory mechanisms in PGD. Epithelial injury-repair markers such as DLK1, surfactant proteins (SFTPA1/2, SFTPB, SFTPC), and SCGB3A2 were downregulated, consistent with epithelial cell loss in PGD 3. By 6 and 12 months, these changes largely resolved (only 8 and 3 DEGs, respectively), suggesting early, transient immune activation and epithelial loss post-PGD. Conclusions PGD in the immediate post-transplant period is marked by a strong but transient immune gene expression signature, with simultaneous activation of pro- and anti-inflammatory pathways, parallel with downregulation of epithelial cell markers due to early epithelial cell loss. The lack of persistent differential gene expression at later time points suggests that early PGD does not translate into durable changes in airway immunity or epithelial function, implying effective resolution of the acute inflammatory insult. This abstract is funded by: NIH
Chen et al. (Fri,) studied this question.