CD4+ memory T cells (Tm) from rheumatoid arthritis peripheral blood (RAPB) or peripheral blood from normal donors produced IL-2, whereas fewer cells secreted IFN-γ or IL-4 after a brief stimulation. RAPB Tm contained significantly more IFN-γ producers than normal cells. Many rheumatoid arthritis (RA) synovial Tm produced IFN-γ alone (40%) and fewer cells produced IL-2 or IL-4. An in vitro model was employed to generate polarized T-helper (Th) effectors. Normal and RAPB Tm differentiated into both IFN-γ- and IL-4-producing effectors. RA synovial fluid (RASF) Tm demonstrated defective responsiveness, exhibiting diminished differentiation of IL-4 effectors, whereas RA synovial tissue (RAST) Tm exhibited defective generation of IFN-γ and IL-4 producers.

Regulatory T cells prevent autoimmunity by suppressing the reactivity of potentially aggressive self-reactive T cells. Contact-dependent CD4+ CD25+ 'professional' suppressor cells and other cytokine-producing CD4+ and CD8+ T-cell subsets mediate this protective function. Evidence will be reviewed that T cells primed with transforming growth factor (TGF)-β expand rapidly following restimulation. Certain CD4+ T cells become contact-dependent suppressor cells and other CD4+ and CD8+ cells become cytokine-producing regulatory cells. This effect is dependent upon a sufficient amount of IL-2 in the microenvironment to overcome the suppressive effects of TGF-β. The adoptive transfer of these suppressor cells generated ex vivo can protect mice from developing chronic graft-versus-host disease with a lupus-like syndrome and alter the course of established disease. These data suggest that autologous T cells primed and expanded with TGF-β have the potential to be used as a therapy for patients with systemic lupus erythematosus and other chronic inflammatory diseases. This novel adoptive immunotherapy also has the potential to prevent the rejection of allogeneic transplants.

In rheumatoid arthritis, T cells and B cells participate in the immune responses evolving in the synovial lesions. Interaction between T cells and B cells is probably antigen specific because complex microstructures typical of secondary lymphoid organs are generated. Differences between patients in forming follicles with germinal centers, T-cell–B-cell aggregates without germinal center reactions, or loosely organized T-cell–B-cell infiltrates might reflect the presence of different antigens or a heterogeneity in host response patterns to immune injury. Tertiary lymphoid microstructures in the rheumatoid lesions can enhance the sensitivity of antigen recognition, optimize the collaboration of immunoregulatory and effector cells, and support the interaction between the tissue site and the aberrant immune response. The molecular basis of lymphoid organogenesis studied in gene-targeted mice will provide clues to why the synovium is a preferred site for tertiary lymphoid tissue. B cells have a critical role in lymphoid organogenesis. Their contribution to synovial inflammation extends beyond antibody secretion and includes the activation and regulation of effector T cells.

The synovial tissue in rheumatoid arthritis (RA) patients is enriched with mature antigen presenting cells (APCs) and many T lymphocytes. Interactions between APCs and T cells are essential for the initiation and amplification of T-cell-dependent immune responses, and may therefore play an important role in the chronic inflammatory processes in the synovium. The nature of the antigen(s) involved in RA still remains elusive. However, interactions and signaling through the costimulatory molecules CD28-CD80/86 and CD40-CD40L are critical during APC–T cell interaction for optimal cell activation. This review discusses how such costimulatory signals can be involved in the initiation and amplification of the inflammatory reactions in the synovium. Blocking of the signaling pathways involved in APC–T cell interactions might provide a specific immuno-therapeutic approach for the treatment of RA.

IL-10 is an anti-inflammatory cytokine produced in the joint in rheumatoid arthritis by macrophages and infiltrating blood lymphocytes. Regulation of its expression is poorly understood, but previous findings have suggested that physical interactions with T cells may play a role. This report investigates signalling mechanisms involved in the production of macrophage IL-10 upon interaction with fixed, cytokine-stimulated T cells (Tck). Elutriated monocytes were differentiated to macrophages by macrophage-colony-stimulating factor (M-CSF) and co-cultured with fixed T cells chronically stimulated in a cytokine cocktail of IL-2/IL-6/tumour necrosis factor (TNF)-α in the presence or absence of wortmannin and LY294002, inhibitors of phosphatidylinositol 3-kinase (PI3K), or of rapamycin, an inhibitor of p70 S6-kinase (p70S6K). Spontaneous IL-10 production by rheumatoid arthritis synovial-membrane mononuclear cells (RA-SMCs) and co-cultures of rheumatoid arthritis T cells (RA-Ts) and macrophages was also assessed. RA-T and Tck induction of macrophage IL-10 production was suppressed by cell separation and inhibition of PI3K and p70S6K. PI3K involvement was also shown by phosphorylation of the downstream effector protein kinase B. Spontaneous IL-10 production by RA-SMCs was also inhibited by LY294002 and depletion of the nonadherent (T-cell-enriched) fraction of the cell population. IL-10 production in RA-SMCs and M-CSF-primed macrophages, activated by interaction with Tck, is PI3K- and p70S6K-dependent.

The immunodominant T-cell epitope that is involved in collagen-induced arthritis (CIA) is the glycosylated type II collagen (CII) peptide 256-270. In CII transgenic mice, which express the immunodominant CII 256-270 epitope in cartilage, the CII-specific T cells are characterized by a partially tolerant state with low proliferative activity in vitro, but with maintained effector functions, such as IFN-γ secretion and ability to provide B cell help. These mice were still susceptible to CIA. The response was mainly directed to the glycosylated form of the CII 256-270 peptide, rather than to the nonglycosylated peptide. Tolerance induction was rapid; transferred T cells encountered CII within a few days. CII immunization several weeks after thymectomy of the mice did not change their susceptibility to arthritis or the induction of partial T-cell tolerance, excluding a role for recent thymic emigrants. Thus, partially tolerant CII autoreactive T cells are maintained and are crucial for the development of CIA.

Mechanisms whereby T lymphocytes contribute to synovial inflammation in rheumatoid arthritis are poorly understood. Here we review data that indicate an important role for cell contact between synovial T cells, adjacent macrophages and fibroblast-like synoviocytes (FLS). Thus, T cells activated by cytokines, endothelial transmigration, extracellular matrix or by auto-antigens can promote cytokine, particularly TNFα, metalloproteinase production by macrophages and FLS through cell-membrane interactions, mediated at least through β-integrins and membrane cytokines. Since soluble factors thus induced may in turn contribute directly to T cell activation, positive feedback loops are likely to be created. These novel pathways represent exciting potential therapeutic targets.

Background The development and activation of CD4+ helper T cell (Th) subsets with distinct patterns of unbalanced production of cytokines play an important part in infectious, allergic and autoimmune diseases. Human neonatal cord blood CD4+ Th cells can be polarized into type 1 or type 2-like effector cells in vitro by culturing them in the presence of interleukin (IL)-12 or IL-4, respectively. We have exploited this experimental system to identify marker genes that are differentially expressed by polarized Th1 and Th2 cells. An oligonucleotide microarray specifically designed to screen for inflammation-related candidate genes was used and the differential expression was further validated with a quantitative real-time RT-PCR method. Results In addition to the previously described marker genes of Th cells, we report subtle changes in the expression of several other genes that represent growth factors, receptors and other signaling molecules in polarized Th1 and Th2 cell subsets. Additionally, we describe a novel set of genes as Th1/Th2 differentiation markers for cells activated by anti-CD3 and anti-CD28 antibodies. Conclusions This study demonstrates the power of the targeted use of microarrays in combination with quantitative real-time RT-PCR in identifying and validating new marker genes for gene expression studies.

The cytokine tumour necrosis factor (TNF)α is a vital mediator of the innate immune response, and a pleiotropic regulator of cellular function. Its involvement in rheumatoid arthritis is illustrated by the clinical benefits of TNFα blockade. Post-transcriptional regulation (the control of mRNA stability and translation) appears to play a critical role in the regulation of TNFα expression by mitogen activated protein kinase signal transduction pathways and by anti-inflammatory agents. The aim of this article is to review some recent advances in our understanding of these processes, and to speculate on mechanisms of regulation of TNFα and other pro-inflammatory genes.

Anti-tumor-necrosis-factor-α (TNF-α) monoclonal antibody was used to treat Tg197 transgenic mice, which constitutively produce human TNF-α (hTNF-α) and develop a progressive polyarthritic disease. Treatment of both young (7- or 8-week-old) and aged (27- or 28-week-old) mice commenced when at least two limbs showed signs of moderate to severe arthritis. The therapeutic efficacy of anti-TNF-α antibody was assessed using various pathological indicators of disease progression. The clinical severity of arthritis in Tg197 mice was significantly reduced after anti-TNF-α treatment in comparison with saline-treated mice and in comparison with baseline assessments in both young and aged mice. The treatment with anti-TNF-α prevented loss of body weight. Inflammatory pathways as reflected by elevated circulating hTNF-α and local expression of various proinflammatory mediators were all diminished by anti-TNF-α treatment, confirming a critical role of hTNF-α in this model of progressive polyarthritis. More importantly, the amelioration of the disease was associated with reversal of existing structural damage, including synovitis and periosteal bone erosions evident on histology. Repair of cartilage was age dependent: reversal of cartilage degradation after anti-TNF-α treatment was observed in young mice but not in aged mice.