Difference in B cell activation between dermatomyositis and polymyositis: analysis of the expression of RP105 on peripheral blood B cells
- Y Kikuchia,
- S Koaradaa,
- Y Tadaa,
- O Ushiyamaa,
- F Moritoa,
- N Suzukia,
- A Ohtab,
- T Horiuchid,
- K Miyakec,
- K Nagasawaa
- aDepartment of Internal Medicine, Saga Medical School, 5–1–1 Nabeshima, Saga 849–8501, Japan, bDepartment of Nursing, Saga Medical School, cDepartment of Immunology, Saga Medical School, dFirst Department of Internal Medicine, Faculty of Medicine, Kyushu University, 3–1–1 Maidashi, Higashi-ku, Fukuoka 812–8582, Japan
- Dr Kikuchi
- Accepted 3 May 2001
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.
CONCLUSION 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.