Neutrophil antibody specificity in different types of childhood autoimmuneneutropenia

Autoimmune neutropenia (AIN) in children can be divided into 2 forms. In pr imary AIN, neutropenia is the sole abnormality, and although neutrophil cou nts are generally below 500 mu L-1, mild bacterial infections occur. Primar y AIN is mostly seen in young children and shows a self-limited course. AIN occurring in association with autoimmune diseases (secondary AIN) often sh ows more severe infectious complications. We analyzed clinical and serologi cal data from 28 pediatric patients with AIN to evaluate whether there is a possible relationship between specificity of the neutrophil autoantibodies and the clinical course of the disease. Specificity of the circulating ant ibodies was determined with the indirect granulocyte immunofluorescence tes t (GIFT) and a panel of phenotyped donor neutrophils. The samples were furt her analyzed in the monoclonal antibody immobilization of granulocyte antig ens assay (MAIGA) for neutrophil antigen (NA)1, NA2, CD11a, and CD11b speci ficity. With the indirect GIFT, an antibody specificity was deduced in 26 o f the 28 analyzed samples. In all but 3 sera from patients with primary AIN , NA1-(76%) or NA2-(10%) specific antibodies were detected with the indirec t GIFT. In 2 samples, the reactivity in the indirect GIFT was too weak to d raw conclusions, but the MAIGA showed NA1 and/or NA2 specificity of the ant ibodies. One serum, from a patient with primary AIN with a persistent neutr openia for more than 6 years, contained NA1, possibly pan-Fc gamma RIIIb, a nd CDIIa antibodies. In 4 sera from patients with primary AIN, weak antibod ies with CD11a or CD11b specificity were detected with the MAIGA. Sera from 7 patients with secondary AIN contained in all cases antibodies with pan-F c gamma RIIIb specificity, as deduced from the indirect GIFT results and ab sorbance/ elution experiments performed with 2 sera. The MAIGA confirmed th is for only 1 of the 5 tested sera, Furthermore, CD11a antibodies were dete cted in 1 of the 5 tested sera. In conclusion, our results indicate that pr imary AIN is usually associated with NA-specific antibodies, whereas second ary AIN seems to be associated with pan-Fc gamma RIIIb antibodies. Thus, ch aracterization of the antibodies in sera from children with AIN discriminat es patients with primary AIN from those with secondary AIN. (C) 1999 by The American Society of Hematology.