Neutrophil antigens and antibodies in the diagnosis of immune neutropenias

Neutrophil specific antigens (NA) are expressed exclusively on human neutrophils and were identified using alloantibodies. Neutrophil specific antigens are polymorphic, and several of them (NA1, NA2, NB1, NB2, NC1, ND1, NE1, and 9A), are thought to define genes at different loci. Feto-maternal incompatibility of NA has resulted in alloimmune neonatal neutropenia. Also, NA are the target antigens for autoantibody production in infants and young children with autoimmune neutropenia of infancy and chronic idiopathic neutropenia in adults. Autoimmune neutropenia can occur secondary to several other diseases, including AIDS. Numerous assays are useful in detecting granulocyte antibodies in patients with neutropenia. Among these assays, granulocyte agglutination (GA) and granulocyte immunofluorescence (GIF) are available in some clinical laboratories. Both IgG and IgM agglutinins are detected by GA: in addition, IgG, IgM, and IgA are detected by GIF. Immune neutropenia (IN) occurs in all age groups. Originally thought to be rare, IN is being increasingly recognized in recent years. Further investigations should lead to a greater understanding of the role of NA in immune neutropenias and to identify as yet unknown NA specificities. With the availability of reproducible and sensitive assays to detect granulocyte antibodies and the increasing knowledge and understanding of various disease aspects of IN, proper diagnosis and appropriate clinical management are being applied.