Antibodies, antineutrophilic cytoplasmic

Definition
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Group of predominantly antilysosomal autoantibodies (mostly IgG), which are primarily detected using indirect immunofluorescence techniques. Three different fluorescence patterns are observed, which leads to the classification into three subtypes: cANCA (classical ANCA), pANCA (perinuclear ANCA), atypical ANCA (aANCA or xANCA) (see Table 1).
Occurrence in vasculitis, chronic inflammatory rheumatic syndromes, chronic liver and intestinal diseases and infections. ANCA-associated vasculitides include Wegener's granulomatosis, Churg-Strauss syndrome and microscopic polyangiitis.

General information
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ANCA cytokine sequence theory: Under proinflammatory cytokine influence, translocation of intracellular ANCA target antigens onto the cytoplasmic membrane of neutrophils and monocytes and secretion of adhesion molecules (e.g. ICAM) of neutrophils and endothelial cells. Degranulation of granulocytes with endothelial cell damage and consecutive necrotizing vasculitis. Blocking of the natural deactivation of the receptor molecule protease 3 by ANCA. For vasculitis with additional symptoms in the upper respiratory tract, lung and/or kidney, ANCA-associated vasculitis must be considered, see Table 2.

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Diagnosis
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The standard screening method is ANCA detection with indirect immunofluorescence technique (fluorescent antibodies against granulocyte-bound ANCA). ELISA, RIA, immunoblotting and immunoprecipitation are also possible.

Literature
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Day CJ et al (2003) New developments in the pathogenesis of ANCA-associated vasculitis. Clin Exp Rheumatol 21(6 Suppl 32): S35-48
Gross WL et al (1995) ANCA-associated vasculitis. Dermatologist 46: 511-524
Kallenberg CG et al (2002) New insights into the pathogenesis of antineutrophil cytoplasmic autoantibody-associated vasculitis. Autoimmune Rev 1: 61-66
Keogh KA et al (2003) Churg-Strauss syndrome: clinical presentation, antineutrophil cytoplasmic antibodies, and leukotriene receptor antagonists. On J Med 115: 284-290

Tables
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ANCA subtypes, target antigens and associated diseases (according to Gross WL and Schmitt WH)

Acronym	Target antigen(s)	Associated diseases
cANCA	Proteinase 3 = PR3	Wegener's granulomatosis; more rarely in microscopic polyangiitis, Churg-Strauss syndrome and amoeba-induced liver abscess
pANCA	myeloperoxidase (MPO)	Microscopic polyangiitis, renal vasculitis (idiopathic rapid-progressive GN)
	lactoferrin, cathepsin G, elastase, lysozyme	Inflammatory rheumatic diseases like rheumatoid arthritis and vasculitis, SLE, Sjögren's syndrome
a/pANCA	BPIa (= CAP57)?	Ulcerative colitis, primary sclerosing cholangitis, 10-20% Crohn's disease

ANCA in vasculitis, collagenosis and other rheumatic diseases (according to Gross WL and Schmitt WH)

	Entity	CANCA [%]	pANCA [%]	Target antigen(s)
Vasculitides	Wegener's granulomatosis (initial phase)	50	< 5	PR3a
	Wegener's granulomatosis (generalisation)	90	< 5	PR3a
	Churg-Strauss Syndrome	20	20	PR3, MPOa
	Microscopic polyangiitis	10	60
	Purpura Beauty Enoch	-	< 5
	cryoglobulinemic vasculitis	-	-
	Leucocytoclastic vasculitis	-	-
	polyarteritis nodosa	< 5	< 5
	Kawasaki's Arteritis	-	-
	Giant Cell Arteritis	-	5
	Takayasu arteritis	-	-

Collagenoses and related inflammatory rheumatic diseases	SLE	-	25	LF, HLE, LZb
	Sjögren's Syndrome	-	25	LF, HLE, CG, LZb
	Polymyositis	-	< 10
	Rheumatoid Arthritis	-	20	LF, HLE, CG, LZb
	rheumatoid vasculitis	-	50	LF, HLE, CG, LZb
	Felty Syndrome	-	50	LF, HLE, CG, LZb
	Spondylarthritides	-	< 10