Monocytes and T Lymphocytes Contribute to a Predominance of Interleukin 6 and Interleukin 10 in Systemic Lupus Erythematosus

Objective: To investigate the contribution of T lymphocytes and monocytes to cytokine production in systemic lupus erythematosus (SLE). Methods: Forty-five SLE patients and 19 healthy volunteers were included. Serum levels of tumor necrosis factor alpha (TNF alpha), interferon gamma (IFN gamma), interleukin (IL)-6, and IL10 were quantified by ELISA. The cytokine production capacities of peripheral blood mononuclear cells were assessed by culturing in vitro with PMA+Ionomycin or LPS. The intracellular cytokine expression was measured by flow cytometry in T lymphocytes and monocytes, respectively. The influence of the disease activity (measured as the SLE-disease activity index; SLEDAI) and the treatment the patients were receiving was evaluated. Results: Serum IL10, IL6, and TNF alpha levels were increased in patients (P <= 0.01), and a higher spontaneous (without stimuli) intracellular expression of IL10 in CD4+ and CD8+ T lymphocytes (P < 0.05) and of IL6 in monocytes (P = 0.01) were found. After stimulation, patients presented a higher percentage of CD4+ and CD8+ T lymphocytes producing IL4 and IL10 (P <= 0.01), and of monocytes producing IL6 (P = 0.04) and IL10 (P = 0.008). The SLEDAI score was positively correlated with the percentage of CD4+IL10+ and CD8+IL10+ T lymphocytes (P < 0.01), and inversely correlated with CD8+TNF alpha+ (P = 0.02), CD4+IFN gamma+ (P = 0.04) and CD8+IFN gamma+ (P = 0.002) T lymphocytes. Patients receiving high dose prednisone produced higher IL10, but they also were the patients with a more active disease. Conclusion: Monocytes and T lymphocytes (CD4+ and CD8+) contribute to an overproduction of IL6 and IL10 in SLE; this correlates with the disease activity but is independent of the treatment the patients are receiving. (C) 2009 Clinical Cytometry Society