François Fossiez

Human interleukin-17 : A T cell-derived proinflammatory cytokine produced by the rheumatoid synovium

OBJECTIVE To investigate the presence and role of interleukin-17 (IL-17) in rheumatoid arthritis (RA), and its regulation by antiinflammatory cytokines. METHODS The production of IL-17 was measured in supernatants of RA, osteoarthritis (OA), and normal synovial tissue pieces cultured ex vivo. Quantification of IL-17 was performed using a specific biologic assay. IL-17 gene expression was investigated by reverse transcriptase-polymerase chain reaction (RT-PCR)-techniques. Immunohistochemistry was used to evaluate the frequency of IL-17-positive cells in synovium. The secretion of IL-17 by synovium was measured in the presence of IL-4, IL-13, and IL-10. In addition, the contributions of exogenous and endogenous IL-17 to IL-6 production by RA synovium were studied. RESULTS Functional IL-17 was spontaneously produced by 16 of 18 RA (mean +/- SEM 41.7+/-11.4 units/ml), 2 of 12 OA (5.3+/-4.5 units/ml), and 0 of 3 normal synovial explant cultures. IL-17 messenger RNA expression was demonstrated by RT-PCR in 4 of 5 RA and 0 of 3 OA synovial samples. By immunostaining of RA synovium, IL-17-producing cells were found in the T cell-rich area. Addition of both IL-4 and IL-13 completely inhibited the production of IL-17, whereas IL-10 had no effect. Addition of exogenous IL-17 to RA synovium resulted in an increase in IL-6 production, whereas that of a blocking anti-IL-17 antibody reduced production of IL-6. CONCLUSION The T cell cytokine IL-17 was found to be highly produced by RA, but not by OA, synovium. Its production and function were down-regulated by IL-4 and IL-13. These results indicate that IL-17 contributes to the active, proinflammatory pattern that is characteristic of RA. Through the contribution of IL-17, some Th1-like T cells appear to mediate synovial inflammation.

Identification of Mouse Langerin/CD207 in Langerhans Cells and Some Dendritic Cells of Lymphoid Tissues

Human (h)Langerin/CD207 is a C-type lectin of Langerhans cells (LC) that induces the formation of Birbeck granules (BG). In this study, we have cloned a cDNA-encoding mouse (m)Langerin. The predicted protein is 66% homologous to hLangerin with conservation of its particular features. The organization of human and mouse Langerin genes are similar, consisting of six exons, three of which encode the carbohydrate recognition domain. The mLangerin gene maps to chromosome 6D, syntenic to the human gene on chromosome 2p13. mLangerin protein, detected by a mAb as a 48-kDa species, is abundant in epidermal LC in situ and is down-regulated upon culture. A subset of cells also expresses mLangerin in bone marrow cultures supplemented with TGF-β. Notably, dendritic cells in thymic medulla are mLangerin-positive. By contrast, only scattered cells express mLangerin in lymph nodes and spleen. mLangerin mRNA is also detected in some nonlymphoid tissues (e.g., lung, liver, and heart). Similarly to hLangerin, a network of BG form upon transfection of mLangerin cDNA into fibroblasts. Interestingly, substitution of a conserved residue (Phe244 to Leu) within the carbohydrate recognition domain transforms the BG in transfectant cells into structures resembling cored tubules, previously described in mouse LC. Our findings should facilitate further characterization of mouse LC, and provide insight into a plasticity of dendritic cell organelles which may have important functional consequences.

Expression and activity of IL-17 in cutaneous T-cell lymphomas (mycosis fungoides and sezary syndrome)

Interleukin‐17 (IL‐17) is a proinflammatory cytokine mainly produced by activated CD4+ CD45RO T cells. In mice, we have demonstrated that, depending on the model, IL‐17 may act as a tumor growth‐promoting or ‐inhibiting factor. In order to address the relevance of these models in human tumors, we look for the natural expression and activity of IL‐17 in mycosis fungoides (MF) and Sezary syndrome (SS). These cutaneous T‐cell lymphomas were selected because they are usually CD3+ CD4+ CD45RO+, a phenotype similar to nontransformed T cells producing IL‐17. We show that in vitro activated malignant T cells derived from MF or SS patients express IL‐17 mRNA and secrete this cytokine. However, IL‐17 does not act in vitro as a growth factor for MF or SS cell lines. In addition, 5 out of 10 MF/SS biopsies expressed IL‐17 mRNA, while this cytokine was not detected in normal skin. IL‐17 was not observed in the biopsies derived from 2 patients initially identified as MF, whereas an upregulation of this cytokine was clearly demonstrated during progression of the disease in these patients. An association between IL‐17 expression and polymorphonuclear neutrophil infiltration was also recorded in this group of MF/SS patients. A more detailed analysis of 2 patients with a pustular form of MF and SS revealed that IL‐17 may participate in the recruitment of polymorphonuclear neutrophils via a paracrine mechanism involving keratinocyte‐released IL‐8. This study is the first report demonstrating that some human tumor cells could express IL‐17, a cytokine that represents an early event in the development of the inflammatory reaction within the tumor microenvironment, a process that may influence tumor phenotype and growth.

Generation and characterization of a human monoclonal autoantibody that acts as a high affinity interleukin-1α specific inhibitor

Interleukin-1 (IL-1) defines two polypeptides, IL-1α and IL-1β, that possess a wide spectrum of biological effects. Two natural antagonists of IL-1 action have been characterized: the IL-1 receptor antagonist (IL-1Ra) and a soluble form of the type II IL-1 receptor. Neutralizing autoantibodies to IL-1α have also been detected in sera of healthy individuals and patients with autoimmune or inflammatory diseases. To characterize such antibodies molecularly, we attempted to generate B cell clones producing anti-IL-1α human monoclonal antibody (HuMAb) by combining Epstein-Barr virus-immortalization and CD40-activation of B lymphocytes from individuals with circulating anti-IL-1α. We describe herein the generation and properties of a natural IgG4κ anti-IL-1α monoclonal autoantibody, HuMAb X3, that bound specifically to human IL-1α, but not to IL-1β and IL-1Ra, with a high affinity (Kd = 1.2 × 10−10 M). HuMAb X3 inhibited IL-1α binding to IL-1 receptors and neutralized biological activities of both recombinant and natural forms of IL-1α. A recombinant form of HuMAb X3 was found to display identical specific IL-1α antagonism. The presence of somatic mutations within X3 variable regions suggests an antigen-driven affinity maturation. This study extends the demonstration of the presence of high affinity neutralizing anti-IL-1α autoantibodies that can function as a third type of IL-1 antagonist.

HIGH LEVELS OF NEUTRALIZING AUTOANTIBODIES AGAINST IL-1ALPHA ARE ASSOCIATED WITH A BETTER PROGNOSIS IN CHRONIC POLYARTHRITIS : A FOLLOW-UP STUDY

Neutralizing autoantibodies to interleukin (IL)‐1α were detected in a subset of chronic polyarthritis patients characterized by an increased proportion of patients with primary Sjögrens syndrome or self‐limiting inflammatory arthritis, diseases with a much better prognosis than rheumatoid arthritis (RA). The evolution of anti‐IL‐1α antibody levels was followed over 3 years. Incidence and levels were higher in patients with a benign form of polyarthritis. In these patients levels remained stable or increased over the follow‐up period. In contrast, incidence and levels were lower and some RA patients became negative. Negative correlations were observed between the levels of anti‐IL‐1α antibodies and the clinical and biological indices of disease activity. The relative risk factor of developing RA was 12 in the absence of high anti‐IL‐1α antibody levels and 18.2 when associated with the presence of HLA‐DR4. In conclusion, the presence of anti‐IL‐1α autoantibodies appears to be protective and their detection could represent a marker of good prognosis for destruction.

Control of tumor development by intratumoral cytokines.

The local immune reactions may influence the clinical outcome of human tumors. In carcinoma of the cervix, high gene expression of IL6 with tumor invasiveness whereas lack of gene expression of IFNbeta is correlated with poor prognosis. In colorectal cancer, lack of expression of IFNbeta is associated with the presence of distant metastasis and poor survival. The production of IL17 and IL18, inducers of IL6 and IFNbeta respectively is regulated in these tumors and may control the levels of the effector cytokines, i.e. IL6 and IFNbeta. The mechanisms by which these cytokines act are linked to the recruitment of effector cells such as macrophages.

Increased incidence of neutralizing autoantibodies against interleukin-1α (IL-1α) in nondestructive chronic polyarthritis

Cytokines such as IL-1 and tumor necrosis factor a (TNFa) play a critical role in chronic joint inflammation and destruction. To study their regulation, we looked for circulating antiproinflammatory cytokine autoantibodies in 318 patients with chronic arthritis by immunoprecipitation with protein G. Anti-IL-1α but not anti-IL-1β or anti-TNFα IgG antibodies were detected in 9% of blood donors and 18.9% of chronic arthritis patients. These antibodies were found more commonly and at a higher level in patients with nondestructive arthritis. Negative correlations were observed between the antibody levels and indices of disease activity and joint destruction. There was a negative association between the presence of anti-IL-1α antibodies and that of HLA-DR4. These circulating anti-IL-1α antibodies were not complexed with IL-1α and could block specifically the biological activity of IL-1α and its binding to membrane IL-1 receptors. These results indicate that these antibodies are beneficial, suggesting their contribution in the clinical presentation.