Apoptotic cell clearance in systemic lupus erythematosus. II. Role of beta2-glycoprotein I.
OBJECTIVE
To analyze the contribution of beta2-glycoprotein I (beta2-GPI) to apoptotic cell recognition by antiphospholipid antibodies (aPL) and macrophages from patients with autoimmune disease.


METHODS
Phosphatidylserine expression by Jurkat cells undergoing apoptosis upon CD95 crosslinking or ultraviolet irradiation was verified by confocal microscopy of cells stained with fluorescein isothiocyanate-labeled annexin V. Beta2-GPI was purified by heparin/cationic-exchange chromatography and was biotinylated or used to purify beta2-GPI-specific antibodies by affinity chromatography. Binding to apoptotic cells was assessed by flow cytometry. The clearance of 3H-labeled, apoptotic cells by macrophages was assessed by beta counting.


RESULTS
The array of epitopes generated by beta2-GPI association with apoptotic cells specifically targets their recognition and is required for their opsonization by human aPL. Nevertheless, beta2-GPI is not required for apoptotic cell clearance by human macrophages in the absence of aPL.


CONCLUSIONS
The proinflammatory clearance of aPL-opsonized apoptotic cells, but not the nonphlogistic clearance of apoptotic cells by scavenger macrophages, depends on beta2-GPI.
Manfredi
A A
AA
Istituto Scientifico H. S. Raffaele, and Università di Milano, Milan, Italy.
Rovere
P
P
Heltai
S
S
Galati
G
G
Nebbia
G
G
Tincani
A
A
Balestrieri
G
G
Sabbadini
M G
MG
D017152:Antibodies, Antiphospholipid / Q000276:immunology; D017209:Apoptosis / Q000502:physiology*; D006023:Glycoproteins / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D019169:Jurkat Cells; D008180:Lupus Erythematosus, Systemic / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology*; D008264:Macrophages / Q000502:physiology; D009895:Opsonin Proteins / Q000276:immunology; D010718:Phosphatidylserines / Q000378:metabolism; D053482:beta 2-Glycoprotein I
D017152:Antibodies, Antiphospholipid; D006023:Glycoproteins; D009895:Opsonin Proteins; D010718:Phosphatidylserines; D053482:beta 2-Glycoprotein I