Intracytoplasmic Cytokine Expression and T Cell Subset Distribution in the Peripheral Blood of Patients with Ankylosing Spondylitis

Objective: To determine the role of inflammatory mediators in the pathogenesis of ankylosing spondylitis (AS), we investigated peripheral blood lymphocyte subsets and their intracellular cytokine production.

Methods: The percentages of T and B lymphocytes, natural killer (NK) cells, activated T lymphocytes, CD4+ T helper (Th), and CD8+ T cytotoxic (Tc) cells were determined by flow cytometry in 42 patients with AS compared to 52 healthy controls. In order to assess circulating Th1/Th2 and Tc1/Tc2 subsets, we used a whole-blood cytometric assay based on the intracellular interferon-gamma, interleukin 4 (IL-4), and IL-10 expression of the cells.

Results: In the peripheral blood, the frequencies of CD4+ T helper and CD56+ NK cells were higher in AS (54.8% and 16.2%, respectively) compared to controls (45.3% and 10.8%) (p < 0.05). The frequencies of Th0 (1.9% vs 0.8%) and Tc0 (2.1% vs 0.8%) cells were higher, while that of Tc1 cells was lower (26.6% vs 40.1%) in patients with AS versus controls (p < 0.05). The percentage of IL-10-producing Tc cells was significantly higher in AS (18.4%) versus controls (8.5%) (p < 0.05). Finally, the active phase of AS was associated with significantly lower percentage of IL-10-producing Tc cells in the peripheral blood (6.6%) compared to patients with inactive AS (23.1%).

Conclusion: Our results provide further evidence for an altered T cell subset distribution and intracytoplasmic cytokine balance in AS.