Chimeric antibodies to proteinase 3 of IgG1 and IgG3 subclasses induce different magnitudes of functional responses in neutrophils.
BACKGROUND
Antineutrophil cytoplasmic antibodies (ANCA) are associated with small-vessel vasculitis and have been implicated in its pathogenesis. The subclass distribution of ANCA IgG deviates from normal patterns, and it has been suggested that the IgG3 subclass may have pathogenic potential over the IgG1 subclass and may be more likely to be associated with active disease and renal involvement.


OBJECTIVE
To deal with potential pathogenicity, chimeric antibodies were constructed of IgG1 and three subclasses with human IgG1 or three constant regions and a murine-derived variable region that binds an epitope within the ANCA antigen proteinase 3 (PR3) that is recognised by human autoantibodies.


METHODS
The antibodies were characterised for binding to PR3, including affinity and avidity, before being used as tools to explore their ability to activate human neutrophils for superoxide release, cytokine release, degranulation and ability to induce neutrophil adhesion under flow.


RESULTS
Both subclass antibodies elicited similar neutrophil responses for superoxide release, degranulation and interleukin (IL) 8 production, although quantitative responses showed that the IgG1 subclass favoured degranulation and the IgG3 subclass favoured IL8 production. Both antibodies were able to convert neutrophils from selectin-dependent rolling adhesion to integrin-dependent stationary adhesion in a flow assay.


CONCLUSIONS
These findings indicate that humanised antibodies directed against a single epitope of PR3 can recapitulate the effects of polyclonal human ANCA, which recognises multiple PR3 epitopes. Further, PR3-ANCA of both IgG1 and IgG3 subclasses can activate neutrophils, although the more potent IL8 response by IgG3 PR3-ANCA may encourage further neutrophil recruitment and amplify injury.
Colman
Rachel
R
Wellcome Trust Clinical Research Facility, University Hospital Birmingham Foundation Trust, Queen Elizabeth Hospital, Birmingham, UK.
Hussain
Abdullah
A
Goodall
Margaret
M
Young
Steven P
SP
Pankhurst
Tanya
T
Lu
Xiaomei
X
Jefferis
Royston
R
Savage
Caroline O S
CO
Williams
Julie M
JM
D000818:Animals; D019268:Antibodies, Antineutrophil Cytoplasmic / Q000276:immunology*; D000915:Antibody Affinity / Q000276:immunology; D002448:Cell Adhesion / Q000276:immunology; D002478:Cells, Cultured; D006224:Cricetinae; D016207:Cytokines / Q000276:immunology; D004306:Dose-Response Relationship, Immunologic; D000939:Epitopes / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000096:biosynthesis / Q000276:immunology*; D051379:Mice; D053146:Myeloblastin / Q000276:immunology*; D009504:Neutrophils / Q000276:immunology*; D010196:Pancreatic Elastase / Q000276:immunology; D017452:Receptors, IgG / Q000276:immunology; D015398:Signal Transduction / Q000276:immunology; D013481:Superoxides / Q000276:immunology
D019268:Antibodies, Antineutrophil Cytoplasmic; D016207:Cytokines; D000939:Epitopes; D007074:Immunoglobulin G; D017452:Receptors, IgG; D013481:Superoxides; D010196:Pancreatic Elastase; D053146:Myeloblastin