A22-17 Examining the Role of T Cells and T Cell Subset Expression Markers in the Pathophysiology of Lymphangioleiomyomatosis

Abstract Rationale Lymphangioleiomyomatosis (LAM) occurs predominantly in premenopausal women, with features consistent with a slow growing, metastatic neoplasm. A key aspect is the development of diffuse cystic lung disease, with evidence of smooth muscle like LAM cells within the lung parenchyma. Immune cell behaviour within the LAM lung microenvironment is poorly understood, with evidence of LAM cell immune evasion through mechanistic target of rapamycin (mTOR) dependent pathways. Infiltration of T cells around LAM nodules has been described, with evidence of inefficiencies in tumour burden control. The aim of our study is to examine the role of T cells within LAM and further characterise their function within the LAM lung microenvironment. Methods Serum samples of LAM patients and healthy controls were obtained. Immune populations were profiled by flow cytometry using CD45, Siglec-8, CD14, CD15, CD19, and CD3 antibodies; T cells were further characterized with CD4, CD8, CD25, PD-1, and CD69. Clinical characteristics of LAM patients were collected in order to identify those on mTOR inhibitor treatment. FlowJo software was used to define cell populations by applying a gating strategy, with statistical analysis carried out with GraphPad Prism. Previously published spatial transcriptomics dataset (10.1172/jci.insight.187899) were reanalysed to spatially resolve T cell-enriched domains and gene expression patterns within the microenvironment. T cell regions were identified using canonical markers (CD3D, CD3E, TRAC, TRBC1) and validated against Human Lung Cell Atlas reference signatures. Results Analysis of immune cell populations revealed reduced T cells (p = 0.031) in LAM (n = 17) versus control (n = 14). T cell CD4 counts were reduced within the untreated LAM population (n = 9) versus control (n = 11). T cell CD4 expression marker analysis revealed increased PD-1 levels (p = 0.028) in LAM (n = 15) versus control (n = 11). T cell CD8 expression marker analysis also revealed increased PD-1 levels (p = 0.045), as well as increased CD25 levels (p = 0.044) in LAM versus control. Spatial transcriptomics revealed donor-specific T cell infiltration patterns: LAM1 showed compartmentalized perilesional positioning while LAM2 demonstrated diffuse stromal infiltration. Both donors exhibited significant upregulation of T cell-recruiting chemokines (CCL19 p 10−8, CXCL9 p 10−6, CCL5 p 0.05) in enriched domains, supporting CCR7/CXCR3-mediated peripheral-to-tissue trafficking. Conclusions T cell populations are abnormal in LAM, with reduced levels evident in the periphery. T cell subset expression markers reveal evidence of abnormal T cell activation and exhaustion. Spatial analysis confirmed heterogeneous T cell infiltration in LAM with robust chemokine-mediated recruitment signatures, supporting the hypothesis of peripheral T cell reduction to tissue trafficking. This abstract is funded by: None