Downregulation of RCAS1 and upregulation of cytotoxic T cells affects synovial proliferation and apoptosis in rheumatoid arthritis.
OBJECTIVE
The main histological change in rheumatoid arthritis (RA) is the villous proliferation of synovial lining cells. This seems to be the result of the proliferation and apoptosis induced by immune balance. We studied the involvement of RCAS1 and the infiltration of cytotoxic T lymphocytes (CTL), and examined the synovium immunohistochemically to determine the involvement of proliferation and apoptosis in synovial lining cells, and their relationship with the activity of RATreg cells in the germinal center.


METHODS
We used double-immunological staining of Ki-67 and caspase-3 to investigate proliferation and apoptosis. We analyzed CTL, regulatory T cells (Treg), and receptor-binding cancer antigen expressed on SiSo cells (RCAS1), recently recognized to play a role in immune evasion. Proliferation and apoptosis were more frequently encountered in synovial lining cells in RA than in those in osteoarthritis (OA) that were used as a control.


RESULTS
High expression of RCAS1 was detected more frequently in the synovial lining cells of OA, but CTL infiltration into the synovium was rarely found. In RA, on the other hand, CTL were observed, while RCAS1 expression was lacking. We compared the presence of Foxp3-positive cells with the level of C-reactive protein (CRP) that served as an active inflammatory marker. Foxp3-positive cells in the germinal center and in CRP showed possible correlation in terms of the range of inflammatory states.


CONCLUSIONS
In RA, the lack of RCAS1 is thought to induce CTL infiltration through loss of the ability to evade immune attack, thus leading to apoptosis of the synovial lining cells. In addition, Treg cells may play a role in the downregulation of activated T cells.
Yoshida
Shiro
S
Department of Pathology, School of Medicine, Kurume University, Kurume, Japan. marine7blue@hotmail.com
Higuchi
Fujio
F
Ishibashi
Yumiko
Y
Goto
Masafumi
M
Sugita
Yasuo
Y
Nomura
Yuko
Y
Karube
Kennosuke
K
Shimizu
Kei
K
Aoki
Ryosuke
R
Komatani
Hideki
H
Hashikawa
Keiko
K
Kimura
Yoshizo
Y
Nakashima
Manabu
M
Nagata
Kensei
K
Ohshima
Koichi
K
D000951:Antigens, Neoplasm / Q000378:metabolism*; D017209:Apoptosis; D001172:Arthritis, Rheumatoid / Q000276:immunology* / Q000473:pathology; D002097:C-Reactive Protein / Q000032:analysis; D053148:Caspase 3 / Q000378:metabolism; D049109:Cell Proliferation; D015536:Down-Regulation; D051858:Forkhead Transcription Factors / Q000378:metabolism; D018858:Germinal Center / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D019394:Ki-67 Antigen / Q000378:metabolism; D013583:Synovial Membrane / Q000276:immunology* / Q000473:pathology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology* / Q000473:pathology; D050378:T-Lymphocytes, Regulatory / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D015854:Up-Regulation
D000951:Antigens, Neoplasm; C120762:EBAG9 protein, human; C418974:FOXP3 protein, human; D051858:Forkhead Transcription Factors; D019394:Ki-67 Antigen; D002097:C-Reactive Protein; D053148:Caspase 3