B cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL) are members of the tumour necrosis factor superfamily. We have examined circulating BAFF and APRIL in relation to serological deviations and lymphoid organization in the salivary glands of the chronic, autoimmune disorder Sjögren's syndrome. Lymphoid organization in the shape of ectopic germinal centers were detected in 33 of 130 consecutive minor salivary gland biopsies and coincided with increased focus score and elevated levels of serum IgG. Follicular dendritic cell networks, proliferation of mononuclear cells and altered B/T cell ratio also separated the two subgroups. Serum levels of sBAFF and sAPRIL were increased in Sjögren's syndrome compared to healthy blood donors, especially in anti-Ro/La+ patients. Though the differences could not be related to germinal center formation, positive correlations between serum levels of sBAFF and sAPRIL, focus score and IgG denotes their possible role in the disease progression of primary Sjögren's syndrome.

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Functionally impaired B cells play an important role in the pathogenesis of Sjögren's syndrome (SS). The aim of the study was to investigate the apoptosis susceptibility of peripheral blood B cells from patients with SS and the impact of B cell activating factor (BAFF) on the apoptosis capability of these cells in correlation with IgG production. Peripheral blood B cells were isolated and stained for apoptosis markers (Bax, Bcl-2) and members of the TNF-R superfamily, CD95 and CD40. The apoptosis frequency of cells bearing these markers were assessed. Also, the apoptosis capability of cultured B-lymphocytes was investigated in medium alone, with anti-CD95 or with soluble BAFF. Quantitative ELISA was performed to detect plasma levels of sBAFF. Furthermore, the level of circulating B-cell cytokines was measured. BAFF levels were compared between patients with normal and elevated IgG levels. In SS, Bcl-2 positive B cell counts were significantly higher then in controls, also in this population the apoptosis frequency was reduced. Apoptosis within Bax+ and CD40+ B cells were significantly decreased in patients. BAFF induced a significant antiapoptotic effect in SS; also this effect was clearly evident in B cells from SS with hypergammaglobulinaemia. Plasma BAFF levels were significantly higher in SS, mostly in patients with hypergammaglobulinaemia. Plasma B-cell cytokines were raised in SS. In Sjögren's syndrome B cells, a general antiapoptotic tendency might lead to prolonged B-cell survival driven at least partly by elevated levels of BAFF and supposedly by B-cell cytokines. Also, the exaggerated BAFF stimulation might lead to excessive immunoglobulin production. The B-cell apoptosis defects, the increased BAFF levels-correlating with hypergammaglobulinaemia-together with the raised B-cell cytokine levels indicates the disturbed B-cell biology in the disease.

SUMMARY:Because peripheral blood mononuclear cells play an important role in the perpetuation of the autoimmune process in rheumatoid arthritis (RA) and because the maintenance of these cells might be caused by the dysregulation of apoptosis, we investigated the apoptosis susceptibility of peripheral blood mononuclear cells from patients with RA. Freshly separated peripheral blood lymphocytes were stained for apoptosis markers (CD95, Bax, Bcl-2, TNF receptor) and for an activation marker (CD45-RO), and the apoptosis frequency of cells bearing these markers were assessed by the terminal-deoxynucleotidyl transferase-mediated dUTP digoxigenin nick end labeling method and nuclear condensation analysis with laser scanning cytometry. Also, the ability of CD4 ϩ and CD8 ϩ T-cell populations to undergo apoptosis was investigated with 24-hour culture in medium alone or with different apoptosis inducers (anti-CD3, anti-CD95, anti-TNF receptor). Laser scanning cytometry analysis was used to enumerate the phenotype and apoptosis ratios of both freshly isolated and cultured lymphocytes. Quantitative ELISA was performed to detect plasma levels of TNF-␣ and soluble Fas ligand. Furthermore, we studied the relationship between marked apoptotic defects in patients with RA and the severity of clinical disease. CD4 ϩ T-cell counts in patients with RA were elevated compared with controls. A decreased rate of anti-CD95-mediated apoptosis was found within the CD4 ϩ and CD8 ϩ lymphocytic subpopulations. In patients with RA, decreased Bax expression and decreased apoptosis rate within the Bax-positive cells were found, whereas Bcl-2 expression was elevated. The CD45-RO expression was higher, whereas the apoptosis within CD45-RO ϩ cells were decreased in RA. Evaluation of plasma soluble Fas ligand revealed significantly decreased levels in patients compared with controls. The reduced susceptibility to CD95-mediated apoptosis may contribute to the expansion of an activated CD4 ϩ lymphocyte subpopulation and thus to the maintenance of peripheral autoreactive T-cell clones in RA. We also revealed a relationship between in vitro demonstrated lymphocyte apoptosis defects and clinical disease activity.

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