Increased IL-22- and IL-17A-Producing Mucosal-Associated Invariant T Cells in the Peripheral Blood of Patients With Ankylosing Spondylitis

To analyze the frequency, surface phenotype, and cytokine secretion of CD4+ T cells in peripheral blood mononuclear cells (PBMCs) from patients with ankylosing spondylitis (AS) compared with both healthy control subjects and patients with rheumatoid arthritis (RA). Eight-color flow cytometry was used to analyze the surface phenotype and cytokine production of PBMCs from 20 patients with AS, 12 patients with RA, and 16 healthy control subjects, following stimulation ex vivo with phorbol myristate acetate and ionomycin for 5 hours. Secretion of interleukin-17 (IL-17) by PBMCs was measured by enzyme-linked immunosorbent assay, following stimulation with anti-CD3/CD28 for 4 days. The percentages of IL-17-positive CD4+ T cells and IL-22-positive CD4+ T cells were increased in the PBMCs of both patients with AS and patients with RA compared with healthy control subjects, whereas there were no differences in the percentages of interferon-gamma (IFNgamma)-positive or IL-10-positive CD4+ T cells. Likewise, concentrations of IL-17 in supernatants from patients with AS were significantly higher compared with those from healthy control subjects. In patients with RA, the concentrations of IL-17 were increased but not significantly. There was a correlation between the percentages of IL-17-positive CD4+ T cells detected in PBMCs and the amounts of IL-17 in culture supernatants (r=0.414, P=0.0034). All IL-17-producing cells were CD4+CD45RO+; most expressed both CCR6 and CCR4, but only 50% expressed the IL-23 receptor (IL-23R). Nevertheless, there was a positive relationship between the percentage of IL-23R-positive CD4+ T cells and the frequency of IL-17-positive CD4+ T cells or IL-22-positive CD4+ T cells (r=0.57, P<0.0001 and r=0.46, P=0.001, respectively). A significant proportion of cells that produced IL-17 also produced IL-22 and IFNgamma, but none produced IL-10. The frequencies of IL-17-positive and IL-22-positive CD4+ T cells were increased in PBMCs from patients with AS and patients with RA, resulting in secretion of higher quantities of IL-17 by PBMCs following stimulation. These data support the hypothesis that Th17 cells, particularly when present in excess of IL-10-producing cells, are involved in the pathogenesis of inflammatory arthritis.

Biological agents have dramatically improved treatment options for patients with severe psoriasis. Etanercept (tumor necrosis factor [TNF] receptor–immunoglobulin fusion protein) is an effective treatment for many psoriasis patients, and blockade of TNF is considered to be its primary action. However, in this clinical trial, we show that etanercept has early inhibitory effects on a newly appreciated type of T cells: T helper type 17 (Th17) cells. Etanercept reduced the inflammatory dendritic cell products that drive Th17 cell proliferation (interleukin [IL] 23), as well as Th17 cell products and downstream effector molecules (IL-17, IL-22, CC chemokine ligand 20, and β-defensin 4). In contrast, Th1 cellular products and effector molecules (interferon γ, lymphotoxin α, and myxovirus resistance 1) were reduced late in disease resolution. This study suggests a role for Th17 in addition to Th1 cells in the pathogenesis of psoriasis. Th17 cells may be particularly important in driving epidermal activation in psoriatic plaques, whereas Th1 cells must also be eliminated for final disease resolution.

A distinct subset of proinflammatory CD4+ T cells that produce interleukin-17 was recently identified. These cells are implicated in different autoimmune disease models, such as experimental autoimmune encephalomyelitis and collagen-induced arthritis, but their involvement in human autoimmune disease has not yet been clearly established. The purpose of this study was to assess the frequency and functional properties of Th17 cells in healthy donors and in patients with different autoimmune diseases. Peripheral blood was obtained from 10 psoriatic arthritis (PsA), 10 ankylosing spondylitis (AS), 10 rheumatoid arthritis (RA), and 5 vitiligo patients, as well as from 25 healthy donors. Synovial tissue samples from a separate group of patients were also evaluated (obtained as paraffin-embedded sections). Peripheral blood cells were analyzed by multiparameter flow cytometry and immunohistochemistry. Cytokine production was examined by enzyme-linked immunosorbent assay and intracellular cytokine staining using specific monoclonal antibodies. Synovial tissue was examined for infiltrating T cells by immunohistochemical analysis. We found increased numbers of circulating Th17 cells in the peripheral blood of patients with seronegative spondylarthritides (PsA and AS), but not in patients with RA or vitiligo. In addition, Th17 cells from the spondylarthritis patients showed advanced differentiation and were polyfunctional in terms of T cell receptor-driven cytokine production. These observations suggest a role of Th17 cells in the pathogenesis of certain human autoimmune disorders, in particular the seronegative spondylarthritides.