Patients with systemic lupus erythematosus and secondary antiphospholipid syndrome have decreased numbers of circulating CD4⁺CD25⁺Foxp3⁺ Treg and CD3⁻CD19⁺ B cells

Abstract

Introduction: CD4+CD25+Foxp3+ regulatory T (Treg) cell depletion has been reported in systemic lupus erythematosus (SLE) and, recently, in primary antiphospholipid syndrome (APS); the issue has not been studied in SLE patients with secondary APS (SLE/APS) so far.

Objective: To quantify total lymphocytes, Treg cells, CD3+CD19- T cells and CD3-CD19+ B cells in SLE/APS patients and healthy controls.

Methods: Cell subtypes underwent immunophenotyping using specific monoclonal antibodies (anti-CD3 CY5, anti-CD4 FITC, anti-CD25, anti-Foxp3, anti-CD19 PE) and flow cytometry.

Results: Twenty-five patients with SLE/APS (mean age 43.5 years, 96% females, 96% caucasians, mean duration of disease 9.87 years, mean SLEDAI 10 ± 5.77) and 25 age and sex-matched controls entered the study. It was realized that the numbers of Treg and CD3- CD19+ B cells were significantly lower in SLE/APS patients than in controls (all p < 0.05).Treg and CD3-CD19+ B cells remained numerically low after controlling (ANCOVA) for percentage of total lymphocytes (p < 0.05). Decreasing levels of circulating Treg and CD3-CD19+ B cells correlated to higher scores of lupus activity (rs = -0.75, p < 0.0001; rs = -0.46, p = 0.021, respectively). Number of Treg cells and CD3-CD19+ B lymphocytes did not significantly differ in users or nonusers of chloroquine, azathioprine and corticosteroids (all p > 0.05).

Conclusions: In this preliminary study, patients with SLE and secondary APS showed depletion of Treg and CD3-CD19+ B cells; decreasing numbers of both subtypes correlated to a higher SLEDAI. Treg cells depletion might contribute to the autoimmune lesion seen in patients with SLE/APS. The reduced number of CD3-CD19+ B cells seen in these patients deserves more studies in order to get further elucidation.