Anti-HLA antibody binding to HLA class I molecules induces proliferation of airway epithelial cells: A potential mechanism for bronchiolitis obliterans syndrome

Objective: Development of anti-HLA antibodies is associated with development of bronchiolitis obliterans syndrome after lung transplantation. We sought to determine the mechanism by which anti-HLA antibodies affect the development of bronchiolitis obliterans syndrome. We postulated that anti-HLA antibodies bind to the donor lung epithelium and stimulate phosphorylation and proliferation. Methods: The A549 lung epithelial carcinoma cell line was cultured in serum-deficient medium to produce static growth. Then the cells were treated with anti-HLA sera from lung transplant recipients, pooled anti- HLA serum from highly sensitized patients, or normal human serum. The cells were also treated with the W6/32 mouse anti-HLA class I monoclonal antibody or control mouse IgG. Tritiated thymidine uptake was determined at 24, 48, and 72 hours. In parallel experiments the cells were treated as described above, and the levels of tyrosine phosphorylation were determined by Western blot analysis. Results: Cells treated with anti-HLA serum or the W6/32 monoclonal antibody exhibited significantly greater proliferation and tyrosine phosphorylation of proteins of approximately 170, 130, 110, and 70 kd compared with cells treated with normal human serum or mouse IgG, respectively. Conclusions: These data indicate that anti-HLA antibodies have the ability to stimulate airway epithelial cell proliferation and that they may play an important role in the development of bronchiolitis obliterans syndrome. Prevention of HLA sensitization and immunosuppression with agents capable of blocking indirect antigen presentation and the humoral immune response against the allograft may be pivotal in preventing the development of bronchiolitis obliterans syndrome after lung transplantation.