PR3 Antibodies | MPO Antibodies | GBM Antibodies

PR 3 Antibodies

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Performance folders
EliA PR3 S, MPO S (pdf)
EliA PR3, MPO, GBM (pdf)
Varelisa ANCA (pdf)

Antigens

Antineutrophil cytoplasmic antibodies (ANCA) can be subdivided into cytoplasmic ANCA (cANCA) and perinuclear ANCA (pANCA). The main antigen for the cANCA reactivity is the enzyme proteinase 3 (PR3).

PR3 is a cationic protein consisting of 228 amino acid residues and belonging to the trypsin family of serine proteases. Expressed only in primates and humans, PR3 has various functions, including proteolysis of elastin, haemoglobin, fibronectin, laminin and collagen type IV, and antimicrobial activities, etc.

PR3 in Phadia, now Immunodiagnostics, assays is purified from human neutrophils. 

In EliA PR3 S (sensitive) the wells are coated with the antigen using an anchor technique that substantially increases the sensitivity of the test.

Disease association, antibody prevalence and specificity

• Glomerulonephritis with polyangiitis (GPA), formerly called Wegener's granulomatosis, dependent on disease activity: about 50% in inactive disease, nearly 100% in the active generalization phase of GPA, specificity >95% 
• Microscopic polyangiitis: small percentage 
• Eosinophilic glomerulonephritis with polyangiitis (EGPA), formerly called Churg-Strauss syndrome: 10-30%
• Polyarteritis nodosa: 8-10%  
• Idiopathic crescentic glomerulonephritis: 30%

Information about the diseases

In general, anti-MPO and anti-PR3 do not occur in the same patient concurrently. The detection of c-ANCA with clear PR3 activity is 99% specific for necrotizing small vessel vasculitis.

When is the measurement recommended?

• Suspicion of idiopathic systemic vasculitis, which will arise in the following conditions:
• Presence of visible vascular lesions such as purpura, necrotic fingertips, etc. 
• Presence of more or less typical symptoms such as necrotizing inflammation in the upper airways (GPA), hypereosinophilia with non-allergic asthma (eosinophilic glomerulonephritis with polyangiitis), etc. 
• Rapidly progressive glomerulonephritis
• Presence of symptoms and signs of inflammation such as fever, raised ESR and C-reactive protein level, etc., without identifiable cause or localization

Antibody isotype

IgG

Detection methods

ELISA (with coated PR3) or indirect immunofluorescence (IIF). 90% of cANCA-positive sera are also positive in PR3 ELISA, and vice versa.

References

Gross WL, Csernok E, Szymkowiak CH (1996)  |  Harris A, Chang G, Vadas M, Gillis D (1999)  |  Boomsma MM, Stegeman CA, ven der Leij MJ (2000)   

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MPO antibodies

Promotion material

Performance folders
EliA PR3 S, MPO S (pdf)
EliA PR3, MPO, GBM (pdf)
Varelisa ANCA (pdf)

Antigens

Antineutrophil cytoplasmic antibodies (ANCA) can be subdivided into cytoplasmic ANCA (cANCA) and perinuclear ANCA (pANCA). The main antigen for the pANCA reactivity is the enzyme myeloperoxidase (MPO). MPO is present in and is a marker enzyme of the azurophilic granules of neutrophils. It catalyses the production of hypochloric acid, which is effective in killing phagocytized bacteria and viruses.

MPO makes up almost 5% of the total protein of a neutrophilic granulocyte. It is a covalently linked dimer with a molecular weight of about 140 kDa.

MPO in Phadia, now Immunodiagnostics, assays is purified from human neutrophils.

Antibody specificity and prevalence

• Idiopathic necrotizing and crescentic glomerulonephritis without immune deposits (= pauci-immune): in about 65% 
• Microscopic polyangiitis: 45 % 
• Eosinophilic glomerulonephritis with polyangiitis (EGPA), formerly called Churg-Strauss syndrome: about 60% 
• Glomerulonephritis with polyangiitis (GPA), formerly called Wegener's granulomatosis (WG): 10% 
• Polyarteritis nodosa: about 15% 
• Goodpasture syndrome: about 30-40% 
• SLE: about 8%, but more common in drug-induced lupus

Information about the diseases

In general, anti-MPO and anti-PR3 do not occur in the same patient concurrently. The detection of p-ANCA with clear MPO activity is 99% specific for necrotizing small vessel vasculitis. In contrast, p-ANCA with negative or low positive MPO reactivity are not associated with vasculitis.
A.Wiik, Denmark, suggested the latter be renamed neutrophil-specific autoantibodies rather than ANCA to avoid misinterpretation of results (Carette S., 2004, J Rheumatol 31:792-4).

Disease activity

The relative risk of relapse increases with ANCA positivity.

Table: ANCA persistence or rise should influence therapeutic decision.
(Data from presentation by Jayne J, Geneva, 2002)

ANCA titres are higher during active diseases than in remission.

When is the measurement recommended?

• Suspicion of idiopathic systemic vasculitis, which will arise in the following conditions:
• Presence of visible vascular lesions such as purpura, necrotic fingertips, etc. 
• Presence of more or less typical symptoms such as necrotizing inflammation in the upper airways (GPA), hypereosinophilia with non-allergic asthma (eosinophilic glomerulonephritis with polyangiitis), etc. 
• Rapidly progressive glomerulonephritis 
• Presence of symptoms and signs of inflammation such as fever, raised ESR and C-reactive protein level, etc., without identifiable cause or localization

Antibody isotypes

IgG

References

Kallenberg CGM (1996)  |  Harris A, Chang G, Vadas M, Gillis D (1999)  |  Savage COS, Harper L, Cockwell P, Adu D, Howie AJ (2000)   

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GBM Antibodies

Promotion material

Performance folder
EliA PR3, MPO, GBM (pdf)

Antigens

The main function of the glomerular basement membrane (GBM) of the kidney is ultrafiltration of blood. Type IV collagen is a typical component of the GBM, has self-aggregating properties and forms a matrix in which the other basement membrane molecules are integrated. Type IV collagen forms trimers composed of three subunits of alpha chains. Because the antibodies are directed to epitopes of the so-called non-collagenous domain (NCI domain) hidden inside the protein in its native structure, denatured antigen must be used for the detection of GBM antibodies.

The Varelisa GBM Antibodies and EliA GBM are the first assays using human recombinant NCI domain of collagen IV alpha 3 chain.

Antibody specificity and prevalence

• Rapidly progressing glomerulonephritis (with or without lung haemorrhage) (15%) 
• Goodpasture's syndrome (one of three specific criteria) 
• ANCA-associated vasculitides

Information about Goodpasture's syndrome

In Goodpasture's syndrome, it is important to initiate therapy before renal damage has advanced too far. Early recognition is therefore mandatory and can be confirmed with the use of sensitive assays.

Disease activity

Relatively high antibody titres may persist in patients in clear clinical remission and decline only slowly over a year or so. In general, renal transplantation should be postponed until antibody titration is negative to avoid a recurrence of the disease in the transplant recipient. 

When is the measurement recommended?

• Suspicion of Goodpasture's syndrome 
• Patients with glomerulonephritis 
• Positive ANCA results 
• Before kidney transplantation: indication of a high risk of acute renal failure (poor prognosis)

Antibody isotypes

IgG

References

Hellmark T, Segelmark M, Bygren P, Wieslander J (1996)  |  Kluth DC, Rees AJ (1999)  |  Gibson IW, More IAR (1998)

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