Fcgamma receptors mediate internalization of anti-Ro and anti-La autoantibodies from Sjögren's syndrome and apoptosis in human salivary gland cell line A-253.
BACKGROUND
The presence of serum anti-Ro and anti-La autoantibodies directed against the ribonucleoproteins Ro and La has been associated with Sjögren's syndrome (SS), an autoimmune rheumatic disease that targets salivary and lachrymal glands. There is increasing evidence of the direct involvement of autoantibodies in the pathogenesis of tissue injury and correlation of their presence with clinical manifestations in SS. The focus of this work was to explore the cellular apoptotic pathway triggered by binding and penetration of anti-Ro and anti-La autoantibodies in human salivary gland cell line A-253 and to identify the membrane receptors through which anti-Ro and anti-La could exert their effect.


METHODS
Anti-Ro and anti-La autoantibodies were purified from IgG fractions, obtained from eleven healthy volunteers and patients with primary Sjögren's syndrome, using Sepharose 4B-Ro and Sepharose 4B-La affinity columns. Flow cytometry, RT-PCR, western blot and confocal microscopy analysis were used to visualize the FCgammaRI, FCgammaRII and FCgammaRIII receptors on the A-253 cell membrane. DNA laddering and western blot analysis of caspases activation were studied to evaluate in A-253 cells treated with anti-Ro and anti-La autoantibodies.


RESULTS
The results yeilded the evidence of the presence of members of the Fcgamma receptors (FcgammaRs) family on the cell membrane of the human salivary gland cell line A-253. Furthermore, we demonstrated that, in the A-253 cell line, anti-Ro and anti-La autoantibodies can access the cells probably through Fcgamma receptors, and trigger apoptotis.


CONCLUSIONS
We conclude that anti-Ro and anti-La autoantibodies have pathogenic effects that could depend on binding to Fcgamma receptors.
Lisi
Sabrina
S
Department of Human Anatomy and Histology, University of Bari, Bari, Italy. s.lisi@anatomia.uniba.it
Sisto
Margherita
M
Soleti
Raffaella
R
Saponaro
Concetta
C
Scagliusi
Pasquale
P
D'Amore
Massimo
M
Saccia
Matteo
M
Maffione
Angela B
AB
Mitolo
Vincenzo
V
D017209:Apoptosis; D001323:Autoantibodies / Q000502:physiology*; D001324:Autoantigens / Q000276:immunology; D015153:Blotting, Western; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D004705:Endocytosis; D004789:Enzyme Activation; D005434:Flow Cytometry; D006801:Humans; D017452:Receptors, IgG / Q000032:analysis / Q000502:physiology*; D012261:Ribonucleoproteins / Q000276:immunology; D012469:Salivary Glands / Q000166:cytology*; D012859:Sjogren's Syndrome / Q000276:immunology*; D000097585:SS-B Antigen; D000099207:SS-A Antigen
D001323:Autoantibodies; D001324:Autoantigens; D020169:Caspases; D017452:Receptors, IgG; D012261:Ribonucleoproteins; D000097585:SS-B Antigen; D000099207:SS-A Antigen