To investigate the direct role of interleukin (IL) 6 in the development of rheumatoid arthritis, IL-6-deficient (IL-6 ؊͞؊) mice were backcrossed for eight generations into C57BL͞6 mice, a strain of mice with a genetic background of susceptibility for antigen-induced arthritis (AIA). Both histological and immunological comparisons were made between IL-6-deficient (IL-6 ؊͞؊) mice and wild-type (IL-6 ؉͞؉) littermates after the induction of AIA. Although all IL-6 ؉͞؉ mice developed severe arthritis, only mild arthritis was observed in IL-6 ؊͞؊ mice. Safranin O staining demonstrated that articular cartilage was well preserved in IL-6 ؊͞؊ mice, whereas it was destroyed completely in IL-6 ؉͞؉ mice. In addition, comparable mRNA expression for both IL-1␤ and tumor necrosis factor ␣, but not for IL-6, was detected in the inf lamed joints of IL-6 ؊͞؊ mice, suggesting that IL-6 may play a more crucial role in cartilage destruction than either IL-1␤ or tumor necrosis factor ␣. In immunological comparisons, both antigen-specific in vitro proliferative response in lymph node cells and in vivo antibody production were elicited in IL-6 ؊͞؊ mice, but they were reduced to less than half of that found in IL-6 ؉͞؉ mice. Lymph node cells of IL-6 ؊͞؊ mice produced many more Th2 cytokines than did IL-6 ؉͞؉ mice with either antigen-specific or nonspecific stimulation in in vitro culture. Taken together, these results indicate that IL-6 may play a key role in the development of AIA at the inductive as well as the effector phase, and the blockade of IL-6 is possibly beneficial in the treatment of rheumatoid arthritis.

Objective. To investigate the roles of interleukin-6 (IL-6) in the pathogenesis of rheumatoid arthritis (RA) by studying its effect on murine collagen-induced arthritis (CIA).Methods. IL-6-deficient (IL-6؊/؊) mice with a genetic background of susceptibility to CIA were generated by backcrossing them with DBA/1J mice for 8 generations. Clinical and immunologic features were compared between these mice and IL-6 wild-type (IL-6؉/؉) littermates with CIA.Results. Serum IL-6 levels increased during the development of CIA in IL-6؉/؉ mice. Two prominent peaks were observed. The first was coincident with the onset of arthritis, and the second one was observed during exacerbation of the disease. The onset of arthritis in IL-6؊/؊ mice was delayed for 2 weeks compared with that in IL-6؉/؉ mice, and the severity of arthritis, as indicated by the arthritis score, remained significantly lower in IL-6؊/؊ mice during the entire followup period (14 weeks), although all IL-6؊/؊ mice developed definite arthritis as did the IL-6؉/؉ mice. Histologic severity was also reduced in IL-6؊/؊ mice. In addition, radiologic changes such as osteopenia and bone erosion were reduced significantly in these animals. Both humoral and cellular responses to type II collagen (CII) in IL-6؊/؊ mice were reduced to about half those in IL-6؉/؉ mice. In addition, enhanced production of IL-4 and IL-10 in response to concanavalin A stimulation was observed in IL-6؊/؊ mice.Conclusion. IL-6 plays an important role in the development of CIA, and both suppression of specific immune responses to CII and a tendency to a shift toward a Th2 cytokine profile might contribute in part to the attenuation of CIA in IL-6؊/؊ mice. These findings suggest that blockade of IL-6 might be beneficial in the treatment of RA.

We showed that CD9, a member of tetraspanin superfamily proteins, is expressed in a specific membrane microdomain, called "lipid raft," and is crucial for cell fusion during osteoclastogenesis after activation of the RANK/RANKL system. Introduction: Osteoclasts are bone-resorbing multinuclear polykaryons that are essential for bone remodeling and are formed through cell fusion of mononuclear macrophage/monocyte lineage precursors. Although osteoclastogenesis has been shown to be critically regulated by the RANK/RANKL system, the mechanism how precursor cells fuse with each other remains unclear. We examined the function of CD9, a member of tetraspanin superfamily, which has previously been shown to form macromolecular membrane microdomains and to regulate cell-cell fusion in various cell types. Materials and Methods: We used RAW264.7, a macrophage/monocyte lineage cell line, which can differentiate into osteoclast-like polykaryons on the application of RANKL. Expression and distribution of CD9 was assessed by Western blotting, fluorescence-assorted cell sorting (FACS) and immunohistochemistry with light and electron microscopy. A specific neutralizing antibody and RNA interference were used to inhibit the function of CD9, and green fluorescent protein (GFP)-CD9 was exogenously expressed to enhance the effect of CD9. The distribution of CD9 in lipid microdomain was examined by biochemical (sucrose density gradient) isolation and imaging technique. Results: CD9 is expressed on cell surfaces of RAW264.7, which is enhanced by RANKL. Targeted inhibition of CD9 decreases the number of osteoclast-like cells. On the other hand, overexpression of CD9 promotes spontaneous cell fusion even in the absence of RANKL. CD9 is localized in detergent-insoluble "lipid raft" microdomain in RANKL stimulation, and disruption of lipid rafts markedly reduces the formation of osteoclast-like polykaryons. Immunohistochemical studies of bone tissues revealed the expression of CD9 in osteoclasts in vivo. Conclusions: These data suggest that function of tetraspanin CD9 and its expression in lipid rafts are crucial for cell fusion during osteoclastogenesis.

We have identified the genes whose expressions are augmented in the blood cells of the patients with systemic lupus erythematosus (SLE) using the 'stepwise subtraction' technique along with microarray analysis. The expression levels of these genes were assessed by quantitative real-time reverse transcription polymerase chain reaction (RT-PCR) in 31 SLE patients and 30 healthy controls. We found that the transcription levels of following eight genes were significantly increased in SLE patients; interferon (IFN)-alpha-inducible protein 27 (IFI27), IFN-alpha-inducible protein IFI-15K (G1P2), IFN stimulated gene 20 kDa (ISG20), epithelial stromal interaction 1 (EPSTI1), defensin-alpha (DEFA3), amphiregulin (AREG) and two genes of unknown function (BLAST accession nos AL050290 and AY358224 = SLED1). In comparison with idiopathic thrombocytopenic purpura (ITP), an organ-specific autoimmune disease, IFI27, G1P2 and SLED1 were preferentially upregulated in SLE. In contrast, AREG and AL050290 were more highly expressed in ITP than in SLE. We correlated changes in gene expression and clinical/laboratory features of SLE and found that expression of ISG20, EPSTI1 and SLED1 are significantly correlated with lymphocyte counts. Genes linked to IFN are well known to influence SLE, but several other novel genes unrelated to IFN signaling we report here would be useful to understand the pathophysiology of SLE.

The 105A/C polymorphism of the IL-18 gene may be associated with the pathogenesis of asthma.

We evaluated the diagnostic value of anti-cyclic citrullinated peptide 2 (anti-CCP2) antibodies and other potential diagnostic biomarkers (IgM rheumatoid factor, anti-agalactosyl IgG antibodies, matrix metalloproteinase 3, C-reactive protein) for predicting early development of rheumatoid arthritis (RA). Patients were defined as having recent-onset undifferentiated arthritis (UA) if they had developed arthritis in two or more joints within the previous 2 years and could not be classified with a well-defined arthropathy. Baseline levels of biomarkers were measured in blood samples collected at the entry of the study and the patients were followed for 1 year to monitor development of RA. Diagnoses of RA and non-RA arthropathies were made according to individual standard diagnostic criteria. A total of 146 patients were enrolled in the study. In the follow-up year, 18 patients developed RA, 54 developed non-RA arthropathies, and 60 remained in the UA category. The sensitivity and specificity of the presence of anti-CCP2 antibodies for the diagnosis of RA were 83.3 and 93.0%, respectively. The positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy of anti-CCP2 antibodies for RA (65.2, 97.2, and 91.7%, respectively) were higher than for any other biomarker. Combination of anti-CCP2 with any other biomarker only slightly improved each diagnostic value compared to the presence of anti-CCP2 alone. Among the anti-CCP2-positive patients, the average titer was significantly higher in those with RA than in non-RA or UA patients (163.7 +/- 138.4 vs 55.2 +/- 72.0 U/ml, p = 0.017). Anti-CCP2 antibodies are superior to any other single biomarker for predicting early development of RA in patients with recent-onset UA and the diagnostic value of anti-CCP2 alone is similar to that for biomarker combinations. Moreover, the anti-CCP2 antibody titer is useful to discriminate between patients at high risk for early developing RA from those at risk of developing non-RA arthropathies.

The salivary flow rate and EGF levels are decreased in SS, and this deterioration in saliva quality causes refractory intraoral manifestations. Our findings have provided new therapeutic targets for SS.

IgE synthesis by purified human B cells is induced by two signals: a class switching factor, most commonly interleukin (IL)-4, and the engagement of CD40, which is activated through its interaction with CD40 ligand (CD40L) expressed on activated T cells. Thus, the combination of IL-4 and anti-CD40 monoclonal antibody (mAb) has been shown to stimulate IgE production in vitro by highly purified B cells. In this T cell-independent system, strong homotypic aggregation of B cells is observed prior to the production of IgE. Flow cytometric analysis and cell binding assays showed that the stimulation of purified B cells with anti-CD40 mAb plus IL-4 resulted in a striking increase of intercellular adhesion molecule (ICAM)-1(CD54) expression, an induction of CD43 and an avidity change of lymphocyte functional antigen (LFA)-1(CD11a/CD18), with little augmentation of CD18 expression. Addition of anti-ICAM-1 mAb caused an inhibition of homotypic aggregation but augmented IgE synthesis by B cells stimulated with anti-CD40 mAb and IL-4, although it did not affect B cell proliferation or IL-6 production by the B cells. Among the mAb against counter-receptors for ICAM-1 tested, anti-CD11a mAb suppressed IgE synthesis, while anti-CD18 mAb and anti-CD43 mAb had little effect. The enhancing or inhibitory effect of anti-ICAM-1 mAb or anti-CD11a mAb on IgE production was achieved by the increased or decreased expression of germline C epsilon transcripts by B cells stimulated with anti-CD40 mAb and IL-4. These results indicate that B cell-B cell interaction through ICAM-1 and one of its counter receptors, LFA-1, regulates IgE synthesis by modulating C epsilon germ-line transcription.