A comparison of methods for detecting leukocyte antibodies in autoimmune neutropenia.

A six-month-old girl and an 18-month-old boy with autoimmune neutropenia due to anti-NA1 are described. The antibodies were detected by granulocyte microagglutination, and their disappearance in the girl coincided with a return of a normal neutrophil count. The autoantibodies in both patients also reacted in the granulocyte cytotoxicity (GC) assay, and in one patient, in the staphylococcal protein A (SPA) assay. However, neither the GC nor the SPA assays showed the anti-NA1 specificity found by agglutination, and the presence of GC and SPA antibodies did not coincide with neutropenia. These three leukocyte antibody techniques may detect different antibodies and have different clinical significances. This report provides additional evidence of the existence of autoimmune neutropenia and indicates that the clinical role of neutrophil antibodies detected by different serologic techniques is not yet established. Antibodies detected by granulocyte agglutination were clinically significant in these two patients with autoimmune neutropenia, while the results of testing with GC and SPA were not.