The relationship between alloimmunization and posttransfusion granulocyte survival: experience in a chronic granulomatous disease cohort.

Chronic granulomatous disease (CGD) is a heterogeneous group of inherited disorders characterized by recurrent, often life-threatening, pyogenic infections.1–3 In CGD, abnormalities of the NADPH oxidase system result in failure of neutrophils to produce reactive oxygen intermediates.1–4 The lack of these oxygen species impairs the ability of neutrophils to destroy invading microorganisms and leads to granuloma formation. Interferon-γ (IFN-γ) is used prophylactically to prevent infections through mechanisms that are not well defined.5 Treatment of established infections in CGD is based on administration of antibacterial or antifungal therapy and surgical drainage when appropriate. Granulocyte transfusions have been given to augment the body's defense mechanisms when infections are severe or antimicrobial therapy is thought to be inadequate.2,6–8 Other modes of treatment under investigation include hematopoietic stem cell transplantation and gene therapy to incorporate normal genes for the oxidase system into hematopoietic stem cells.9,10 Although granulocyte transfusions are used empirically to treat patients with infections resulting from CGD, the efficacy of this treatment in patients who become alloimmunized is uncertain. Alloimmunization to both HLA and neutrophil-specific epitopes occurs in up to 78% of CGD patients who have received granulocyte transfusions,7,11 and these antibodies have been shown to destroy transfused granulocytes.12–14 Thus, a single course of granulocyte transfusions can adversely affect the ability to tolerate or obtain benefit from subsequent courses. Even in those who are not alloimmunized, it is difficult to evaluate the respective contributions of granulocytes and antimicrobials to improvements in the patient's condition. Alloimmunization is not the only risk associated with granulocyte transfusions. Acute systemic and pulmonary reactions, including fever, rigors, and respiratory distress, are well documented and are more common in the presence of alloimmunization.7,15–17 The risk of transmission of infectious agents, although very small, is present with any blood component. Despite the ability to prospectively identify alloimmunized patients, it has been difficult to predict which patients will gain clinical benefit from a course of granulocyte transfusions. Under certain conditions, it may be desirable to administer granulocytes to alloimmunized recipients if the potential benefits of therapy are assessed as outweighing the risks. A method that quickly and accurately identifies patients in whom acute severe reactions are likely to occur and clinical benefit would be unlikely would greatly enhance our ability to determine the best course of action. A flow cytometric assay using dihydrorhodamine 123 (DHR) can detect the presence of intact NADPH oxidase activity in neutrophils and quantitate the ability of such cells to undergo a normal respiratory burst.18–21 Since the respiratory burst is impaired in granulocytes from CGD patients, this assay can be used to quantitate and monitor the survival of transfused oxidase-positive granulocytes in these patients. We used the DHR assay as a supplement to HLA serologic screening in the identification of patients at high risk of acute transfusion reactions and at low likelihood of clinical benefit from such transfusions. Ten patients with CGD and life-threatening infections were serially evaluated with HLA serum screens and quantitative DHR assays during the course of daily granulocyte transfusion therapy.