Impact of age and telomere length on circulating T cells and rejection risk after lung transplantation for idiopathic pulmonary fibrosis

PurposeMost idiopathic pulmonary fibrosis (IPF) lung transplant recipients (IPF-LTRs) have short telomere length (ST). Inherited mutations in telomere-related genes are associated with the development of T cell immunodeficiency. Despite this, IPF-LTRs with telomere-related rare variants are not protected from acute cellular rejection (ACR). We set out to determine the impact of both age and telomere length on the circulating T cell compartment and ACR burden of IPF-LTRs.MethodsWe identified 106 IPF-LTRs who had telomere length testing using flowFISH (57 with short telomeres, 49 with long telomers) as well as a subset from both cohorts who had cryopreserved PBMC at least one timepoint, 6 months post-transplantation. Circulating T cells from before transplantation and at 6 and 12 months-post transplantation were analyzed using multiparameter flow cytometry to study phenotype and functional capacity and bulk T cell receptor sequencing was performed to study repertoire diversity. Linear regression was used to study the relationship of age and telomere length on early (within 1 year) and late (between 1 and 2 years) acute cellular rejection.ResultsIPF-LTRs with ST were found to have premature ‘aging’ of their circulating T cell compartment, with age-agnostic elevations in post-transplant terminal differentiation of CD8+ T cells, increased granzyme B positivity of both CD8+ and CD4+ T cells, upregulation of the exhaustion marker, CD57, and chemotactic protein CCR5, and enhanced T cell receptor clonal expansion. Additionally, we found a significant decline in early ACR burden with increasing age, but only in the ST cohort.ConclusionIPF-LTRs with ST have premature ‘aging’ of their circulating T cell compartment post transplantation, and a clear age-related decline in ACR burden.