Analysis of the CD8+ T cell response to the G1 domain of aggrecan in ankylosing spondylitis.
BACKGROUND
CD4+ T cell responses to the G1 domain of aggrecan in patients with ankylosing spondylitis (AS) were recently reported. Whether such an immune response can be seen in the CD8+ subpopulation has not yet been determined.


OBJECTIVE
To determine if HLA-B27 restricted G1-specific CD8+ T cells are present in AS and to analyse immunodominant CD8+ T cell epitopes.


METHODS
Peripheral blood mononuclear cells of 45 patients with AS were stimulated with overlapping 18-mer peptides covering the whole G1 protein. Results were compared with those for patients with rheumatoid arthritis (RA) and healthy controls. For epitope analysis, G1-specific interferon gamma positive (IFNgamma+) T cells were isolated by magnetic activated cell sorting. After in vitro expansion, CD8+ T cells were restimulated with 14 subpools of G1 peptides. T cells responding to G1 peptide subpools were quantified by flow cytometry according to IFNgamma secretion. Predicted peptides were subsequently confirmed by stimulation with single peptides.


RESULTS
G1-specific CD8+ T cell responses were found in 29/45 (64%) patients with AS, 18/35 (51%) patients with RA, but not in healthy controls. Five CD8+ T cell epitopes were identified as immunodominant in five patients. However, the T cell response was not HLA-B27 restricted. Nonamer peptides with an HLA-B27 binding motif did not induce a T cell response.


CONCLUSIONS
A G1 peptide-specific CD8+ T cell response is present in AS but also in patients with RA. It does not seem to be HLA-B27 restricted. Whether such a response has a role in the pathogenesis of AS needs clarification.
Zou
J
J
Department of Gastroenterology and Rheumatology, Charité Berlin, Campus Benjamin Franklin, Hindenburgdamm 30, 12200 Berlin, Germany.
Appel
H
H
Rudwaleit
M
M
Thiel
A
A
Sieper
J
J
D000328:Adult; D053674:Aggrecans; D001172:Arthritis, Rheumatoid / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D002478:Cells, Cultured; D018984:Epitopes, T-Lymphocyte / Q000276:immunology; D016326:Extracellular Matrix Proteins / Q000276:immunology*; D005434:Flow Cytometry; D015796:HLA-B27 Antigen / Q000032:analysis; D006801:Humans; D016056:Immunodominant Epitopes / Q000276:immunology; D007371:Interferon-gamma / Q000097:blood; D037181:Lectins, C-Type; D008213:Lymphocyte Activation / Q000276:immunology; D008875:Middle Aged; D011509:Proteoglycans / Q000276:immunology*; D013167:Spondylitis, Ankylosing / Q000276:immunology*
D053674:Aggrecans; D018984:Epitopes, T-Lymphocyte; D016326:Extracellular Matrix Proteins; D015796:HLA-B27 Antigen; D016056:Immunodominant Epitopes; D037181:Lectins, C-Type; D011509:Proteoglycans; D007371:Interferon-gamma