Expression profile of leukocyte genes activated by anti-neutrophil cytoplasmic autoantibodies (ANCA).
BACKGROUND
Anti-neutrophil cytoplasmic autoantibodies (ANCA) induce neutrophil activation in vitro with release of injurious products that can mediate necrotizing vasculitis in vivo. The importance of ANCA IgG F(ab')2-antigen binding versus Fcgamma receptor engagement in this process is controversial. We propose that ANCA-antigen binding affects cell signaling pathways that can result in changes of gene expression.


METHODS
Microarray GeneChip analysis and real-time, quantitative PCR (TaqMan(R)) was used to probe for transcripts in leukocytes from patients (in vivo gene expression study) and in leukocytes treated with ANCA IgG or ANCA-F(ab')2 (in vitro gene expression study).


RESULTS
Microarray gene chip analysis showed that ANCA IgG and ANCA-F(ab')2 stimulate transcription of a distinct subset of genes, some unique to whole IgG, some unique to F(ab')2 fragments, and some common to both. DIF-2, COX-2, and IL-8 were identified as genes responsive to ANCA signaling and were selected for in depth evaluation. In vitro DIF-2 and IL-8 were increased by both ANCA IgG and F(ab')2, but COX-2 only by MPO-ANCA F(ab')2. In vivo DIF-2 levels were increased in leukocytes of ANCA patients, which correlated strongly with disease activity and ANCA titer. DIF-2 was not increased in patients in remission or in disease control patients (systemic lupus erythematosus and IgA nephropathy). COX-2 gene expression was significantly increased in patients with active disease, while IL-8 was increased in remission.


CONCLUSIONS
The data indicate that leukocyte genes are activated in vitro by both ANCA Fc and ANCA F(ab')2 pathways and that in vitro activation mimics changes in circulating leukocytes of patients with ANCA disease. Increased levels of DIF-2 in patient leukocytes strongly correlate with severity of disease in kidney tissue. The observations indicate a previously unrecognized role for DIF-2 in ANCA-mediated inflammation, which raises the possibility that DIF-2 has an important role in other types of inflammation.
Yang
Jia Jin
JJ
Division of Nephrology, Department of Medicine, The University of North Carolina, Chapel Hill, North Carolina 27599, USA. jjyang@med.unc.edu
Preston
Gloria A
GA
Alcorta
David A
DA
Waga
Iwao
I
Munger
William E
WE
Hogan
Susan L
SL
Sekura
Stephen B
SB
Phillips
Brian D
BD
Thomas
Robin P
RP
Jennette
J Charles
JC
Falk
Ronald J
RJ
D019268:Antibodies, Antineutrophil Cytoplasmic / Q000276:immunology*; D051017:Apoptosis Regulatory Proteins; D015267:Churg-Strauss Syndrome / Q000276:immunology; D015870:Gene Expression / Q000276:immunology*; D014890:Granulomatosis with Polyangiitis / Q000276:immunology; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics; D007140:Immunoglobulin Fab Fragments / Q000276:immunology; D007074:Immunoglobulin G / Q000276:immunology; D066298:In Vitro Techniques; D008565:Membrane Proteins; D009363:Neoplasm Proteins / Q000235:genetics; D018375:Neutrophil Activation / Q000276:immunology*; D009504:Neutrophils / Q000276:immunology*; D020411:Oligonucleotide Array Sequence Analysis; D013481:Superoxides / Q000378:metabolism; D015533:Transcriptional Activation / Q000276:immunology
D019268:Antibodies, Antineutrophil Cytoplasmic; D051017:Apoptosis Regulatory Proteins; C099815:IER3 protein, human; D017874:Immediate-Early Proteins; D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D013481:Superoxides