Spatial transcriptomics reveals differences in bronchus-associated lymphoid tissue composition in stable and...

Area of Science:

• Transplantation immunology
• Pulmonary pathology
• Spatial transcriptomics

Background:

• Lung allograft rejection is graded by pathologists using transbronchial biopsies (TBBx) per ISHLT criteria.
• Lymphocytic bronchiolitis (LB) diagnosis is challenging due to overlap with bronchus-associated lymphoid tissue (BALT).
• The role of BALT in lung transplant tolerance and rejection remains unclear.

Purpose of the Study:

• To characterize lymphoid aggregates in ISHLT acute cellular rejection (ACR) grades A0 and A3.
• To investigate the relationship between BALT and lung allograft rejection.
• To explore the diagnostic utility of spatial transcriptomics in differentiating BALT and rejection.

Main Methods:

• Review of TBBx for BALT presence.
• Selection of A0 and A3 biopsies for spatial transcriptomics and multiplex immunofluorescence.
• Computational analysis of spatial transcriptomics data for neighborhood analysis and cell cluster identification.

Main Results:

• Spatial transcriptomics identified BALT and rejection lesions, revealing distinct immune cell enrichments in A0 (CXCL9/10+ T, PDL1/L2+ myeloid) and A3 (NKG7+CD8+ T) BALT.
• Higher CXCL9/10 expression in BALT correlated with A0 grade.
• A3 BALT and rejection lesions exhibited significant similarities, with computational methods detecting occult lymphoid aggregates in rejecting lung parenchyma.

Conclusions:

• A link exists between the BALT immune microenvironment and lung allograft rejection.
• Lymphoid infiltration in A3 allografts may be more widespread than visible on H&E staining.
• Spatial transcriptomics offers a powerful tool for characterizing immune infiltrates in lung allografts.