Immunoglobulin levels of children with bronchiolitis obliterans syndrome after hematopoietic cell transplantation

Background: The development of bronchiolitis obliterans syndrome (BOS) following allogeneic hematopoietic stem cell transplantation (allo-HCT) remains an unresolved clinical problem. However, developing a risk stratification tool for BOS risk is challenging as numerous factors contribute to its development. Moreover, allo-HCT may lead to a decrease in respiratory mucosal surface defense function, resulting in recurrent inflammation and fibrosis. Previous studies have shown that immunoglobulin G (IgG) and IgA levels significantly decrease after lung transplantation and are associated with BOS. Therefore, we hypothesized that immunoglobulin levels of patients may also decrease after allo-HCT, and may even be risk factor for the development of BOS. Methods: In this retrospective study, a total of 134 patients were enrolled. According to the presence of BOS, these patients were divided into BOS and non-BOS groups. Clinical information and immunoglobulin levels were analyzed between the two groups. Immunoglobulin levels of patients before and after transplantation were compared. Binary logistic regression and Cox regression were used to identify variables with independent prognostic significance. Results: ABO incompatible, human leukocyte antigen (HLA) mismatch, lung infection within 100 days post-transplantation, cytomegalovirus (CMV) serology positivity, and pre-transplant IgA immunoglobulin deficiency were risk factors for BOS after allo-HCT. Following transplantation, IgA and IgM levels significantly decreased, and many patients had levels below the reference values. In addition, the serum IgA levels prior to transplantation were lower in the BOS group than the non-BOS group. In multivariate models, pre-transplant IgA deficiency was a risk factor for BOS. Conclusion: Following allo-HCT, IgA and IgM levels decreased, and numerous patients had levels below the reference values. In multivariate models, pre-transplant IgA deficiency was identified as a risk factor for BOS.