AntiNeutrophil

Antineutrophil refers to any antibody or other immune factor that targets neutrophils, a type of white blood cell central to innate immunity. In clinical immunology, antineutrophil antibodies can be autoantibodies produced by the patient against its own neutrophils or alloantibodies formed against neutrophils from another individual. These antibodies can cause neutropenia by promoting destruction or clearance of neutrophils, leading to an increased risk of infections. A well-known subset is anti-neutrophil cytoplasmic antibodies (ANCA), which target cytoplasmic enzymes within neutrophils and are associated with certain vasculitic diseases.

Mechanisms and subtypes: Antineutrophil antibodies may bind to surface antigens on neutrophils, triggering complement activation, opsonization, or phagocytic clearance. ANCA, a specific and clinically important group, are detected by Immunofluorescence and antigen-specific assays targeting enzymes such as myeloperoxidase (MPO) and proteinase 3 (PR3). The term also encompasses alloantibodies in alloimmune neutropenia, including neonatal alloimmune neutropenia, where maternal antibodies cross the placenta to affect the infant’s neutrophils, and antibodies formed after transfusion or transplantation.

Clinical relevance: Antineutrophil antibodies are associated with various conditions, including autoimmune neutropenia (congenital or acquired), drug-induced neutropenia, and immune neutropenia following transplantation or transfusion. Their presence is interpreted in the context of clinical findings, as they may be transient or of uncertain significance in some individuals.

Diagnosis and management: Diagnosis relies on serologic testing for antineutrophil antibodies, techniques to detect neutrophil-bound antibodies, and, when relevant, ANCA testing for MPO and PR3. Management focuses on treating infections, addressing the underlying cause, and may involve immunomodulatory therapy or growth factors such as granulocyte colony-stimulating factor in selected cases.