Olfactomedin-4 autoantibodies give unusual c-ANCA staining patterns with reactivity to a subpopulation of neutrophils.
Testing for the presence of ANCAs in circulation is part of the clinical examinations routinely performed upon suspected autoimmune disorders, mainly vasculitis. The autoantibodies are typically directed toward neutrophil MPO or PR3. These are major granule-localized proteins, and similar to all hitherto-described ANCA antigens, they are expressed by all neutrophils, and ANCA-containing sera thus give rise to uniform reactivity toward all neutrophils in a sample. In this paper, we describe sera from 2 unrelated patients with diffuse inflammatory symptoms that gave rise to peculiar c-ANCA patterns, only reacting with a subpopulation (roughly 30%) of human neutrophils. By immunoblotting, both sera reacted to the same antigen, which was expressed in intracellular granules. The antigen could be released to the extracellular milieu through secretion but also through the formation of NETs. Neutrophils have long been considered a homogenous cell population, but it is becoming increasingly clear that distinct subpopulations, defined by the presence or absence of certain proteins, exist. One such marker that defines a neutrophil subset is the granule protein OLFM4. The unusual, subset-restricted c-ANCA sera reacted only with OLFM4-positive neutrophils, and MS analysis revealed that the autoantigen was, in fact, OLFM4. These data describe for the first time a c-ANCA pattern reactive to only a subpopulation of neutrophils and identify the granule protein OLFM4 as a novel autoantigen.
Departments of *Rheumatology and Inflammation Research and Oral Microbiology and Immunology, Sahlgrenska Academy at University of Gothenburg, Sweden; Clinical Immunology and Transfusion Medicine, Sahlgrenska University Hospital, Gothenburg, Sweden; and Department of Pulmonary Medicine, Norra Älvsborg County Hospital, Trollhättan, Sweden.
Firoozeh
F
Amirbeagi
Departments of *Rheumatology and Inflammation Research and Oral Microbiology and Immunology, Sahlgrenska Academy at University of Gothenburg, Sweden; Clinical Immunology and Transfusion Medicine, Sahlgrenska University Hospital, Gothenburg, Sweden; and Department of Pulmonary Medicine, Norra Älvsborg County Hospital, Trollhättan, Sweden.
Pontus
P
Thulin
Departments of *Rheumatology and Inflammation Research and Oral Microbiology and Immunology, Sahlgrenska Academy at University of Gothenburg, Sweden; Clinical Immunology and Transfusion Medicine, Sahlgrenska University Hospital, Gothenburg, Sweden; and Department of Pulmonary Medicine, Norra Älvsborg County Hospital, Trollhättan, Sweden.
Rille
R
Pullerits
Departments of *Rheumatology and Inflammation Research and Oral Microbiology and Immunology, Sahlgrenska Academy at University of Gothenburg, Sweden; Clinical Immunology and Transfusion Medicine, Sahlgrenska University Hospital, Gothenburg, Sweden; and Department of Pulmonary Medicine, Norra Älvsborg County Hospital, Trollhättan, Sweden.
Bo
B
Pedersen
Departments of *Rheumatology and Inflammation Research and Oral Microbiology and Immunology, Sahlgrenska Academy at University of Gothenburg, Sweden; Clinical Immunology and Transfusion Medicine, Sahlgrenska University Hospital, Gothenburg, Sweden; and Department of Pulmonary Medicine, Norra Älvsborg County Hospital, Trollhättan, Sweden.
Bengt A
BA
Andersson
Departments of *Rheumatology and Inflammation Research and Oral Microbiology and Immunology, Sahlgrenska Academy at University of Gothenburg, Sweden; Clinical Immunology and Transfusion Medicine, Sahlgrenska University Hospital, Gothenburg, Sweden; and Department of Pulmonary Medicine, Norra Älvsborg County Hospital, Trollhättan, Sweden.
Claes
C
Dahlgren
Departments of *Rheumatology and Inflammation Research and Oral Microbiology and Immunology, Sahlgrenska Academy at University of Gothenburg, Sweden; Clinical Immunology and Transfusion Medicine, Sahlgrenska University Hospital, Gothenburg, Sweden; and Department of Pulmonary Medicine, Norra Älvsborg County Hospital, Trollhättan, Sweden amanda.welin@gu.se.
Amanda
A
Welin
Departments of *Rheumatology and Inflammation Research and Oral Microbiology and Immunology, Sahlgrenska Academy at University of Gothenburg, Sweden; Clinical Immunology and Transfusion Medicine, Sahlgrenska University Hospital, Gothenburg, Sweden; and Department of Pulmonary Medicine, Norra Älvsborg County Hospital, Trollhättan, Sweden.
Johan
J
Bylund
D000368:Aged; D000369:Aged, 80 and over; D019268:Antibodies, Antineutrophil Cytoplasmic / Q000276:immunology*; D001323:Autoantibodies / Q000276:immunology*; D001324:Autoantigens / Q000276:immunology; D001327:Autoimmune Diseases / Q000276:immunology; D015153:Blotting, Western; D004797:Enzyme-Linked Immunosorbent Assay; D016179:Granulocyte Colony-Stimulating Factor / Q000276:immunology*; D006801:Humans; D008297:Male; D018613:Microscopy, Confocal; D009504:Neutrophils / Q000276:immunology*
D019268:Antibodies, Antineutrophil Cytoplasmic; D001323:Autoantibodies; D001324:Autoantigens; C454127:OLFM4 protein, human; D016179:Granulocyte Colony-Stimulating Factor
NETs; OLFM4; antineutrophil cytoplasmic antibodies; neutrophil extracellular traps; neutrophil subsets; phagocyte