Increase of RP105-lacking activated B cells in the peripheral blood and salivary glands in patients with Sjögren's syndrome.
OBJECTIVE
To quantify the activated B cells in the peripheral blood and salivary glands of patients with Sjögren's syndrome (SS) by analyzing the expression of RP105 molecule on the B cells.


METHODS
The expression of RP105 on the peripheral blood B cells of patients with SS (19 cases) was analyzed by flow cytometry. RP105-positive and negative B cells were sorted and cultured in vitro and the amount of immunoglobulins (IgG and IgM) produced in the supernatant was measured by enzyme-linked immunosorbent assay (ELISA). Salivary gland biopsy samples from 9 SS patients were histologically evaluated and the sequential frozen sections were separately immunostained by anti-RP105 and anti-CD20 monoclonal antibodies.


RESULTS
A significantly higher proportion of peripheral blood RP105-negative B cells was found in SS patients than in healthy individuals. RP105-negative, but not positive, B cells from SS patients were capable of producing IgG and IgM spontaneously in vitro, which was enhanced by the addition of Staphylococcus aureus Cowan I strain (SAC) or IL-6. Salivary glands from 2 of 9 SS patients were found to have lymphoid follicles whose germinal centers consisted of RP105-negative B cells. Moreover, a larger proportion of B cells extensively infiltrating the area other than lymphoid follicles was also RP105-negative.


CONCLUSIONS
RP105-negative B cells, a subset of highly activated and well differentiated B cells, which are increased in number in the peripheral blood and extensively infiltrate salivary glands, may be responsible for the production of class-switched immunoglobulin in SS. In addition, those cells might be associated with the inflammation and tissue damage of the salivary glands.
Kikuchi
Y
Y
Department of Internal Medicine, Faculty of Medicine, Saga University, Japan. kikuchi@post.saga-med.ac.jp
Koarada
S
S
Nakamura
S
S
Yonemitsu
N
N
Tada
Y
Y
Haruta
Y
Y
Morito
F
F
Ohta
A
A
Miyake
K
K
Horiuchi
T
T
Nagasawa
K
K
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015703:Antigens, CD / Q000032:analysis* / Q000097:blood; D001402:B-Lymphocytes / Q000737:chemistry*; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis; D007075:Immunoglobulin M / Q000032:analysis; D008213:Lymphocyte Activation / Q000502:physiology; D018655:Lymphocyte Count; D008297:Male; D008875:Middle Aged; D012469:Salivary Glands / Q000166:cytology*; D012859:Sjogren's Syndrome / Q000097:blood / Q000473:pathology*
D015703:Antigens, CD; C092722:CD180 protein, human; D007074:Immunoglobulin G; D007075:Immunoglobulin M