Acute cellular rejection and humoral sensitization in lung transplant recipients

Despite the recent development of many new immunosuppressive agents for use in transplantation, acute cellular and humoral rejection represent extremely prevalent and serious complications after lung transplantation. Acute cellular rejection, defined as perivascular or bronchiolar mononuclear inflammation, affects over 50% of lung transplant recipients within the first year. Furthermore, the frequency and severity of acute rejections are the most important risk factors for the subsequent development of bronchiolitis obliterans syndrome (BOS), a condition of progressive airflow obstruction that severely limits survival after lung transplantation. Treatment options for cellular rejection include high-dose methylprednisolone, antithymocyte globulin, or alemtuzumab. Emerging evidence also suggests that humoral rejection occurs in lung transplantation, characterized by local complement activation or the presence of antibody to donor human leukocyte antigens and is associated with an increased risk for BOS. Treatment options for humoral rejection include intravenous immunoglobulin, plasmapheresis, or rituximab. Herein, we review the clinical presentation, diagnosis, mechanisms, and treatment of cellular and humoral rejection after lung transplantation.