Impaired IgA Mucosal Immunity Following Lung Transplantation: A Potential Trigger for Bronchiolitis Obliterans Syndrome.

Carlier, François;Detry, Bruno;Ambroise, Jérôme;Heddebaut, Nicolas;COLT Consortium;et.al.
(2025) The European respiratory journal — Vol. 66, n° 5, p. 2402212 (2025)

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Abstract
Bronchiolitis obliterans syndrome (BOS) limits long-term survival after lung transplantation (LuTx) and may be triggered by infections. As immunoglobulin (Ig)A is crucial to ensure adequate mucosal immunity, we explored whether IgA-related mucosal immunity is impaired in BOS. Sixty LuTx recipients from the COLT cohort were retrospectively included. All participants were in stable condition within the first year post-transplant. At 3.5 years post-LuTx, 30 remained stable and 30 had developed BOS. Bronchoalveolar lavage fluid (BALF) and sera collected pre-transplant and at 6 (M6) and 12 months (M12) post-transplant were assessed for monomeric IgA, secretory (S)-IgA, secretory component (SC) and cytokine profiling. Second, bronchiolar polymeric Ig receptor (pIgR) expression and subepithelial IgA-producing B-cell numbers were compared across graft tissue samples from 54 LuTx recipients classified as stable, pre-BOS, BOS or end-stage BOS. S-IgA levels in BALF decreased between M6 and M12 (p=0.0001) and were reduced in BOS patients at M12 (p=0.0018). Patients with lower S-IgA levels had higher infection rates. BOS patients exhibited elevated SC levels in serum (p<0.01). Both reduced S-IgA in BALF and increased SC in serum were associated with higher risk of BOS. Lastly, a reduction in bronchiolar pIgR expression was observed in BOS patients (p=0.0001), that paralleled BOS severity. This study demonstrates an early impairment of mucosal IgA immunity in LuTx patients, which was linked to the later development of BOS, suggesting that IgA-related markers may serve as early predictors of BOS onset.
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Carlier, F., Detry, B., Ambroise, J., Heddebaut, N., Plante-Bordeneuve, T., Daumerie, A., Longchampt, E., Falque, L., Reynaud-Gaubert, M., Hirschi, S., Mornex, J.-F., Demant, X., Tissot, A., Le Pavec, J., Bunel, V., Lair, D., Pretolani, M., Vallée, A., Pilette, C., & Brugière, O. (2025). Impaired IgA Mucosal Immunity Following Lung Transplantation: A Potential Trigger for Bronchiolitis Obliterans Syndrome. The European respiratory journal, 66(5), 2402212. https://doi.org/10.1183/13993003.02212-2024 (Original work published 2025)