Difference in B cell activation between dermatomyositis and polymyositis: analysis of the expression of RP105 on peripheral blood B cells.
BACKGROUND
It has previously been shown that RP105, a new B cell surface protein, is lost in activated human B cells.


OBJECTIVE
To investigate whether there is a difference in B cell activation between patients with dermatomyositis (DM) and those with polymyositis (PM) using RP105 as a marker.


METHODS
The population of RP105 negative B cells (activated B cells) in the peripheral blood mononuclear cells of seven patients with dermatomyositis (DM) and 11 with polymyositis (PM) was analysed by flow cytometry.


RESULTS
The percentage of RP105 negative B cells in the peripheral blood of patients with PM was low (5.8 (SD 2.4)%), similar to that of normal subjects. In contrast, all patients with DM showed increased RP105 negative B cell populations (33.0 (6.9)%). Bronchoalveolar lavage fluid from a patient with DM and active interstitial pneumonitis contained a large number of RP105 negative B cells.


CONCLUSIONS
These findings suggest that the expansion of RP105 negative B cells is a hallmark of DM, and that B cell activation in DM may be pathogenetically different from that in PM.
Kikuchi
Y
Y
Department of Internal Medicine, Saga Medical School, 5-1-1 Nabeshima, Saga 849-8501, Japan. kikuchi@post.saga-med.ac.jp
Koarada
S
S
Tada
Y
Y
Ushiyama
O
O
Morito
F
F
Suzuki
N
N
Ohta
A
A
Horiuchi
T
T
Miyake
K
K
Nagasawa
K
K
D000328:Adult; D000368:Aged; D015703:Antigens, CD; D000954:Antigens, Surface / Q000097:blood*; D001402:B-Lymphocytes / Q000276:immunology*; D015415:Biomarkers / Q000097:blood; D001992:Bronchoalveolar Lavage Fluid / Q000276:immunology; D003882:Dermatomyositis / Q000276:immunology; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D017563:Lung Diseases, Interstitial / Q000276:immunology; D008213:Lymphocyte Activation; D008297:Male; D008875:Middle Aged; D017285:Polymyositis / Q000276:immunology*
D015703:Antigens, CD; D000954:Antigens, Surface; D015415:Biomarkers; C092722:CD180 protein, human