Activation of the interferon-gamma signaling pathway in systemic lupus erythematosus peripheral blood mononuclear cells.
OBJECTIVE
To investigate interferon-gamma (IFNgamma) signaling in peripheral blood mononuclear cells (PBMCs) from patients with systemic lupus erythematosus (SLE) by analyzing IFNgamma receptor (IFNgammaR) expression, STAT-1 expression and phosphorylation, and the regulation of IFNgamma-inducible genes.


METHODS
Fluorocytometry was used to investigate expression of STAT-1, pSTAT-1, CD95, HLA-DR, class I major histocompatibility complex (MHC), IFNgamma-inducible 10-kd protein (IP-10), monokine induced by IFNgamma (Mig), and IFNgammaR in PBMCs from SLE patients and healthy individuals. STAT-1 phosphorylation was determined by fluorocytometry and Western blotting after stimulation with IFNalpha or IFNgamma. Quantitative polymerase chain reaction was used to assess messenger RNA (mRNA) expression of the IFNgamma-inducible genes IP-10 and Mig shortly after preparation or after stimulation with IFNgamma in monocytes.


RESULTS
STAT-1 expression was increased in PBMCs from SLE patients and correlated significantly with disease activity and with the IFN-inducible expression of CD95 and HLA-DR. STAT-1 expression also showed a trend toward association with class I MHC expression. In addition, the expression of other IFNgamma-inducible genes, such as IP-10 or Mig, was increased in SLE monocytes. While STAT-1 phosphorylation in SLE PBMCs and PBMCs from healthy individuals was similar after IFNalpha stimulation, incubation with IFNgamma induced STAT-1 phosphorylation only in SLE lymphocytes. Moreover, SLE monocytes showed a considerably higher increase in pSTAT-1 expression upon IFNgamma stimulation than monocytes from healthy individuals. Increased responsiveness of SLE monocytes to IFNgamma was also confirmed on the mRNA level, where expression of the IFN-inducible, STAT-1-dependent genes IP-10 and Mig was more efficiently increased in SLE cells. However, IFNgammaR was similarly expressed on SLE lymphocytes and monocytes and those from healthy individuals.


CONCLUSIONS
In addition to supporting the role of IFNs in SLE immunopathogenesis in general, the findings of the present study support a role of IFNgamma in this disease.
Karonitsch
Thomas
T
Department of Rheumatology, Internal Medicine III, Medical University of Vienna, Vienna, Austria. thomas.karonitsch@meduniwien.ac.at
Feierl
Eva
E
Steiner
Carl Walter
CW
Dalwigk
Karolina
K
Korb
Adelheid
A
Binder
Nikolaus
N
Rapp
Alfred
A
Steiner
Günter
G
Scheinecker
Clemens
C
Smolen
Josef
J
Aringer
Martin
M
D015153:Blotting, Western; D054357:Chemokine CXCL10; D054370:Chemokine CXCL9 / Q000032:analysis; D015870:Gene Expression; D006684:HLA-DR Antigens / Q000032:analysis; D006801:Humans; D007371:Interferon-gamma / Q000502:physiology*; D007963:Leukocytes, Mononuclear / Q000737:chemistry / Q000502:physiology*; D008180:Lupus Erythematosus, Systemic / Q000097:blood*; D008285:Major Histocompatibility Complex; D010766:Phosphorylation; D016133:Polymerase Chain Reaction; D017471:Receptors, Interferon / Q000032:analysis; D050794:STAT1 Transcription Factor / Q000032:analysis; D015398:Signal Transduction; D019014:fas Receptor / Q000032:analysis; D000096743:Interferon gamma Receptor
D054357:Chemokine CXCL10; D054370:Chemokine CXCL9; D006684:HLA-DR Antigens; D007371:Interferon-gamma; D017471:Receptors, Interferon; D050794:STAT1 Transcription Factor; D019014:fas Receptor; D000096743:Interferon gamma Receptor; C114753:CXCL10 protein, human