Intracellular and surface RANKL are differentially regulated in patients with ankylosing spondylitis.
Ankylosing spondylitis (AS) is characterized by ankylosis of axial joints but osteoporosis is also a well-reported feature. T cells have been implicated as a source of receptor activator of NFkappaB ligand (RANKL) in inflammatory bone diseases. Hence, we assessed whether T cells in patients with AS act as a source of RANKL too. Therefore, we investigated the expression of RANKL on T cells from 21 patients with AS by flow cytometry. Bone mineral density (BMD) was evaluated by quantitative computer tomography (QCT) and dual X-ray absorptiometry (DXA) and correlated with serum levels of osteoprotegerin (OPG) and RANKL. BMD was decreased in 45% of all patients when measured with DXA (48% with QCT) and correlated negatively with OPG. Expression of intracellular RANKL was increased on CD4+ (84 vs. 70%) and CD8+ (85.2 vs. 65.3%, P < 0.05) T cells in patients with AS, whereas expression of membrane-bound RANKL was significantly lower (CD4+: 2.2 vs. 8.5% and CD8+: 0.7 vs. 3.2%, P < 0.01). Our results indicate that surface and intracellular RANKL production is differentially regulated on T cells of patients with AS.
Stupphann
Daniela
D
Department of Pathophysiology, Center of Physiology and Pathophysiology, Medical University of Vienna, Vienna, Austria. daniela.stupphann@meduniwien.ac.at
Rauner
Martina
M
Krenbek
Dagmar
D
Patsch
Janina
J
Pirker
Thomas
T
Muschitz
Christian
C
Resch
Heinrich
H
Pietschmann
Peter
P
D015502:Absorptiometry, Photon; D000328:Adult; D000368:Aged; D015519:Bone Density / Q000276:immunology; D001851:Bone Diseases, Metabolic / Q000000981:diagnostic imaging / Q000276:immunology / Q000378:metabolism; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism*; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000000981:diagnostic imaging / Q000276:immunology / Q000378:metabolism; D053244:Osteoprotegerin / Q000097:blood; D053245:RANK Ligand / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism; D013167:Spondylitis, Ankylosing / Q000000981:diagnostic imaging / Q000276:immunology* / Q000378:metabolism*
D053244:Osteoprotegerin; D053245:RANK Ligand; D011956:Receptors, Cell Surface; C505688:TNFSF11 protein, human