Abstract 21

Neutrophil antibodies can cause a variety of disorders including neonatal immune neutropenia, autoimmune neutropenia, immune neutropenia after bone marrow transplantation, drug-induced immune neutropenia and transfusion-related acute lung injury. No single technique is currently available that defects all clinically relevant neutrophil antibodies. A combination of granulocyte agglutination and immunofluorescence tests is currently the most effective means of detection. Due to the autolytic tendency of stored neutrophils, fresh carefully isolated neutrophils have to be used as test cells. The test neutrophils should be typed for the neutrophil antigens NA1, NA2, NB1, SH, and 5b. If it is not possible to determine alloantibody specificity from the reaction pattern with typed test cells, the serum should be tested in an antigen-specific assay based on monoclonal antibody-specific immobilization of granulocytes (MAIGA assay). To avoid cumbersome cell isolation for alloantibody identification, we have established stable mammalian cell lines expressing the neutrophil antigens NA1, NA2, and SH. About 30% of neutrophil autoantibodies show preferential binding to the NA1 antigen and they are best detected using neutrophils from NA1-homozygous donors or NA1 expressing mammalian cells. Autoantibodies are only detected in 74% of the sera during the first round of antibody screening. On the other hand, a positive direct antibody test of the patient's neutrophils cannot be considered as proof for the presence of autoantibodies because the patient's neutrophils are usually activated with increased expression of complement and Fcyreceptors resulting in unspecific IgG binding. Therefore, testing of the patient's sera at intervals for unbound neutrophil antibodies remains the best way for autoantibody detection.