Increased production of soluble CTLA-4 in patients with spondylarthropathies correlates with disease activity.
BACKGROUND
Spondylarthropathies (SpA) are characterized by abnormal immune responses including T cell activation. Cytotoxic T lymphocyte associated molecule-4 (CTLA-4) is involved in down-regulating immune responses. A soluble form of CTLA-4 (sCTLA-4), resulting from an alternative splicing, has been identified and was found increased in several autoimmune diseases. Here, we evaluated circulating levels of sCTLA-4 as a marker of immune dysregulation in SpA. Intracellular CTLA-4 and levels of CTLA-4 transcript expression in peripheral blood lymphocytes (PBL) were also studied.


METHODS
Sera from 165 patients with SpA were evaluated for sCTLA-4 measurements. Results were compared with those from 71 patients with rheumatoid arthritis (RA) and 88 healthy subjects. In 32 patients with SpA, 22 patients with RA and 15 healthy controls, we analyzed the intracellular CTLA-4 expression in CD4+ T cells, CD8+ T cells, activated (HLA-DR+Foxp3-) CD4+ T cells, CD4+ regulatory (CD25+Foxp3+) T cells and in CD3 negative cells by flow cytometry. Expression of the full length (coding for membrane CTLA-4) and spliced form (coding for sCTLA-4) of CTLA-4 transcripts in PBL were analyzed by quantitative real-time polymerase chain reaction (QRT-PCR).


RESULTS
High levels of sCTLA-4 were found in the SpA group compared to the RA group and healthy controls (P < 0.0001). Soluble CTLA-4 serum levels strongly correlated with clinical index of disease activity BASDAI (r = 0.42, P < 0.0001) and C-reactive protein (CRP) levels (r = 0.17, P = 0.037). In contrast to RA patients, SpA patients did not exhibit changes in intracellular CTLA-4 expression in the different PBL subsets tested. Finally, the SpA group showed a preferential expression of the spliced CTLA-4 mRNA (P = 0.0014) in PBL.


CONCLUSIONS
SpA patients exhibit high levels of circulating sCTLA-4 that may result from an alternative splicing of CTLA-4 transcripts. This may influence immune activation and regulation in SpA.
Toussirot
Eric
E
Department of Rheumatology, University Hospital Jean Minjoz, Boulevard Fleming, Besançon cedex, France. etoussirot@chu-besancon.fr
Saas
Philippe
P
Deschamps
Marina
M
Pouthier
Fabienne
F
Perrot
Lucille
L
Perruche
Sylvain
S
Chabod
Jacqueline
J
Tiberghien
Pierre
P
Wendling
Daniel
D
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017398:Alternative Splicing; D015703:Antigens, CD / Q000096:biosynthesis* / Q000097:blood / Q000235:genetics; D060908:CTLA-4 Antigen; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000276:immunology / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D020033:Protein Isoforms / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D025242:Spondylarthropathies / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*; D016176:T-Lymphocyte Subsets / Q000276:immunology / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D055815:Young Adult
D015703:Antigens, CD; D060908:CTLA-4 Antigen; C556706:CTLA4 protein, human; D020033:Protein Isoforms