TOPLINE:

Early impairment of mucosal immunoglobulin A (IgA)-related immunity was associated with the later development of bronchiolitis obliterans syndrome (BOS) in lung transplant recipients; decreased secretory IgA levels and elevated serum secretory component levels predicted the subsequent onset of BOS.

METHODOLOGY:

• BOS is a leading cause of graft failure following lung transplantation and is often triggered by infections that impair airway immunity; IgA is crucial for airway defense, but posttransplant IgA-related immunity is poorly characterized.
• Researchers retrospectively analyzed lung transplant recipients to identify determinants of impaired IgA-related mucosal immunity favoring the development of BOS after transplantation.
• A total of 60 lung transplant recipients were included, of whom 30 were stable (mean age at transplant, 43.9 years; 16 women) and 30 developed BOS (mean age at transplant, 41.5 years; 11 women) during 3.5-year follow-up.
• Bronchoalveolar lavage fluid and serum samples were collected at 6 and 12 months post-transplant to measure total IgA, secretory IgA, and secretory component levels.
• Graft tissue samples from an additional 54 lung transplant recipients at various BOS stages were also evaluated for polymeric Ig receptor expression.

TAKEAWAY:

• Secretory IgA levels differed significantly between recipients who were stable and those with BOS at 12 months (P = .0018); among those with BOS, levels declined significantly between 6 and 12 months (P = .0004), and lower levels at 12 months correlated with a shorter time to BOS diagnosis (P = .01).
• Serum secretory component levels were higher in recipients who developed BOS than in those who were stable at 6 and 12 months (P < .05 for both); a decrease in secretory IgA levels and elevated serum secretory component levels at 12 months were significant determinants of BOS onset.
• Recipients who developed BOS had a higher incidence of infections than those who were stable (P = .0049).
• Polymeric Ig receptor expression was significantly lower in BOS group than in those who were stable, and it was more pronounced in end-stage BOS.

IN PRACTICE:

“[The study] findings highlight the potential relevance of both local (alveolar fluid) and systemic components of IgA-mediated immunity that predicted BOS development, and highlight potential pathways contributing to BOS after lung transplantation,” experts wrote in an editorial accompanying the article.

SOURCE:

This study was led by François M. Carlier, Pôle Pneumologie, ORL et Dermatologie, Institut de Recherche expérimentale et clinique, UCLouvain, Brussels, Belgium. It was published online on November 6, 2025, in European Respiratory Journal.

LIMITATIONS:

Bronchoalveolar lavage fluid samples were not available prior to lung transplantation. The independent effect of immunosuppressive therapy on secretory IgA levels was not directly assessed. Although elevated serum secretory component levels likely reflect increased airway epithelial permeability in patients with BOS, a digestive source could not be entirely excluded. Additionally, missing details on oral corticosteroid maintenance doses may have introduced bias.

DISCLOSURES:

This study was funded by the Vaincre la Mucoviscidose Funds, the Grégory Lemarchal Association, and the Fondation Mont-Godinne, Belgium. The authors reported having no potential conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.