The pIgR/IgA system alteration: an early biomarker for bronchiolitis obliterans syndrome?

<bold>Aims:</bold> Chronic allograft dysfunction (CLAD) hampers longterm survival after lung transplantation (LT). Current CLAD diagnosis criteria fail to detect early pathologic mechanisms. We explored whether the alterations of the pIgR/IgA system observed in obtructive CLAD (BOS) could serve as biomarkers of early BOS. <bold>Methods:</bold> We collected clinical data from LT recipients for whom serum and bronchoalveolar lavage fluid (BALF) were collected at predefined time points prior to the diagnosis of functional stability (n=30) or BOS (n=30). BALF secretory (S-)IgA and serum secretory component were assessed in a previous study(1). <bold>Results:</bold> Using the Youden index, we show that low BALF S-IgA levels at 12 months post-LT and high serum secretory component levels at 6 and 12 months post-LT are strongly associated with the occurence of BOS in the 3-year follow-up (Figure). Similarly, high serum levels at both time points were associated with all-cause mortality, although with less statistical constistency due to the limited number of deaths during the follow-up. <bold>Conclusions:</bold> High serum secretory component levels and low BALF S-IgA, measured before the functional diagnosis of CLAD/BOS, are strongly associated with the occurence of CLAD/BOS. Further studies are required to explore their potential role as biomarkers of early disease. (1) Carlier FM et al. Altered pIgR/IgA mucosal immunity in BOS. J Heart Lung Transplant, 42:4 Supplement, 2023, S140