Impaired function of regulatory T-cells (Treg) leads to a failure in immune tolerance and triggers
autoimmunity. We analyzed whether the deficiency in Treg in systemic lupus erythematosus (SLE) is accompanied
by an increase in effector T-cell responses. We studied the frequencies of IL-17A (Th17) and IFNg (Th1)
producing CD4+ T-cells by flow cytometric detection of intracellular cytokines in PMA/ionomycin stimulated
blood lymphocytes from seven patients with active SLE, eight with SLE in remission, and 11 healthy controls.
Circulating Treg were evaluated as CD4+CD25+ lymphocytes expressing FoxP3. There was no difference in the
percentage of Treg cells between the groups, but their absolute counts were decreased in active SLE (5 [1–7]
cells/μL) compared to inactive SLE (11 [6–15]; p = 0.05) and healthy controls (16 [10–20]; p < 0.01). Both the
frequency and numbers of Th1 cells were decreased in SLE compared to controls. No difference was observed
in the number of Th17 cells, which resulted in a decreased Th1/Th17 ratio. In parallel, a higher Treg/Th17 ratio
in healthy controls (2.2 [1.8–3.6]) compared to active SLE (1.1 [1.0–2.1]; p < 0.05) was observed. There was
a correlation between the number of Treg cells and disease activity status (SLEDAI, r = –0.59). SLE patients in
the active phase of the disease are characterized by a deficiency in Treg cells and decreased Treg/Th17 ratio. This
suggests that the imbalance between major T-cells subsets might be responsible for an increased proinflammatory
response in the exacerbation of SLE. (Folia Histochemica et Cytobiologica 2011; Vol. 49, No. 4, pp. 646–653
