Remnants of secondarily necrotic cells fuel inflammation in systemic lupus erythematosus.
OBJECTIVE
Patients with systemic lupus erythematosus (SLE) are often characterized by cellular as well as humoral deficiencies in the recognition and phagocytosis of dead and dying cells. The aim of this study was to investigate whether the remnants of apoptotic cells are involved in the induction of inflammatory cytokines in blood-borne phagocytes.


METHODS
We used ex vivo phagocytosis assays comprising cellular and humoral components and phagocytosis assays with isolated granulocytes and monocytes to study the phagocytosis of secondarily necrotic cell-derived material (SNEC). Cytokines were measured by multiplex bead array technology.


RESULTS
We confirmed the impaired uptake of various particulate targets, including immunoglobulin-opsonized beads, by granulocytes and monocytes from patients with SLE compared with healthy control subjects. Surprisingly, blood-borne phagocytes from two-thirds of the patients with SLE took up SNEC, which was rarely phagocytosed by phagocytes from healthy control subjects or patients with rheumatoid arthritis. Supplementation of healthy donor blood with IgG fractions derived from patients with SLE transferred the capability to take up SNEC to the phagocytes of healthy donors. Phagocytosis-promoting immune globulins also induced secretion of huge amounts of cytokines by blood-borne phagocytes following uptake of SNEC.


CONCLUSIONS
Opsonization of SNEC by autoantibodies from patients with SLE fosters its uptake by blood-borne monocytes and granulocytes. Autoantibody-mediated phagocytosis of SNEC is accompanied by secretion of inflammatory cytokines, fueling the inflammation that contributes to the perpetuation of autoimmunity in SLE.
Muñoz
Luis E
LE
University Hospital of Erlangen, Department of Radiation Oncology, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen, Germany.
Janko
Christina
C
Grossmayer
Gerhard E
GE
Frey
Benjamin
B
Voll
Reinhard E
RE
Kern
Peter
P
Kalden
Joachim R
JR
Schett
Georg
G
Fietkau
Rainer
R
Herrmann
Martin
M
Gaipl
Udo S
US
D000328:Adult; D000368:Aged; D000888:Antibodies, Anti-Idiotypic / Q000378:metabolism; D017209:Apoptosis / Q000502:physiology*; D016022:Case-Control Studies; D016207:Cytokines / Q000378:metabolism; D004247:DNA / Q000276:immunology; D005260:Female; D006098:Granulocytes / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism; D007249:Inflammation / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology*; D008180:Lupus Erythematosus, Systemic / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009000:Monocytes / Q000378:metabolism / Q000473:pathology; D009336:Necrosis / Q000503:physiopathology; D010586:Phagocytes / Q000378:metabolism / Q000473:pathology; D010587:Phagocytosis / Q000502:physiology
D000888:Antibodies, Anti-Idiotypic; D016207:Cytokines; D007074:Immunoglobulin G; D004247:DNA