Investigating the role of the interleukin-23/-17A axis in rheumatoid arthritis.

OBJECTIVE: IL-23 is a pro-inflammatory cytokine proposed to be central to the development of autoimmune disease. We investigated whether IL-23, together with the downstream mediator IL-17A, was present and functional in RA in humans. METHODS: RA synovial cells were cultured in the presence or absence of antibodies directed against IL-23p19 or -23R and -17. IL-23, -12, -17, and their receptors, and IL-6, -1beta and TNF-alpha were measured by ELISA and/or PCR. RESULTS: Small amounts of cell-associated IL-23 (median 110 pg/ml) were detected in RA synovial cultures, and found to be functional as IL-23R blockade resulting in a significant inhibition of TNF-alpha (57%), IL-1beta (51%) and IL-6 (30%). However, there was a considerable variability between individual patient samples, and anti-IL-23p19 was found to be considerably less effective. IL-17A protein was detected in approximately 40% of the supernatants and IL-17A blockade, in IL-17A-producing cultures, resulted in a small but significant inhibition of TNF-alpha (38%), IL-1beta (23%) and IL-6 (22%). Addition of recombinant IL-23 to cultures had a variable effect on the spontaneous production of endogenous IL-17A with enhancement observed in some but not all cultures, suggesting that either the low levels of endogenous IL-23 are sufficient to support cytokine production and/or that the relevant Th17 cells were not present. CONCLUSIONS: These results suggest that although IL-23 may have pathogenic activity in a proportion of patients with late-stage RA, it is not abundantly produced in this inflammatory tissue, nor does it have a dominant role in all patient tissues analysed.

Glucocorticoids and the emerging importance of T cell subsets in steroid refractory diseases.

Glucocorticoids remain the first-line treatment for a range of autoimmune and allergic diseases. However, 30% of patients fail to achieve disease control at tolerable systemic doses and continue to have an increased immune response with poor clinical outcome. This steroid refractory (SR) phenotype has previously been attributed to enhanced expression of inactive glucocorticoid receptor isoforms and cytokine-mediated suppression of glucocorticoid (GC) signaling, in particular by interleukin-2. These mechanisms are discussed, with emphasis on recent evidence for the role of the CD4(+)CD25(int) and GC-induced T regulatory cell subsets in perpetrating SR disease.

Steroid refractory CD4+ T cells in patients with sight-threatening uveitis.

PURPOSE: A discrete subpopulation of steroid refractory (SR) CD4(+) T cells has recently been identified in patients with SR ulcerative colitis (UC). The purpose of this study was to test whether this subpopulation is also present in patients with clinically defined SR uveitis. As interleukin (IL)-2 experimentally mediates the SR phenotype, the combined effects of dexamethasone (Dex) and a range of IL-2 targeting immunosuppressive agents were also investigated. METHODS: Peripheral blood mononuclear cells (PBMCs) from 27 patients with uveitis and 4 normal volunteers were cultured for 5 days with CD3-CD28 beads. In vitro steroid refractivity or responsiveness was determined by the presence or absence of a subpopulation of SR CD4(+) cells (as previously reported for UC) that continued to proliferate or not in the presence of Dex. The patients were concurrently classified by a masked investigator as having clinically SR (threshold for disease reactivation, >or=10 mg prednisone daily) or steroid sensitive (SS) disease. RESULTS: There was 78% (21/27) agreement between the in vitro and clinical classifications of SR and SS disease (kappa coefficient = 0.56, P = 0.002). This finding corresponds to a positive predictive value of 90% and a negative predictive value of 71%. In normal volunteers, basiliximab, daclizumab, and AG490 achieved an equivalent augmentation of CD4(+) cell suppression in combination with Dex. CONCLUSIONS: As in UC, patients with SR uveitis have a subpopulation of SR CD4(+) cells that are a potential target for intervention with anti-IL-2 therapies, including inhibitors of JAK/STAT signaling. The identification of SR T cells also has potential clinical application as a biomarker for SR disease.

CD4+CD25(int) T cells in inflammatory diseases refractory to treatment with glucocorticoids.

Up to 30% of patients with autoimmune, allergic, and lymphoproliferative diseases are refractory to glucocorticoid therapy. The present study was undertaken to investigate whether such steroid resistance (SR) is limited to a subpopulation of CD4(+) T cells and, as IL-2 is a putative driver of SR, whether T cell SR is associated with CD25 expression. We show that SR patients have a characteristic subgroup of activated CD4(+) T cells that continue to proliferate despite exposure to high-dose Dexamethasone (Dex), demonstrate that CD4(+)CD25(-) cells are exquisitely sensitive to Dex whereas CD4(+)CD25(int) cells are highly SR, and further find that the combination of an anti-CD25 mAb with Dex enhances suppression of T cell proliferation compared with each agent alone. We therefore conclude that SR is not a general property of all lymphocytes but resides in T cell subpopulations, which are prevalent in SR patients and express intermediary levels of CD25. As a result, we propose a new paradigm for SR disease in which glucocorticoid therapy positively selects SR cells, generating a population of drug-resistant lymphocytes that perpetuate on-going inflammation.