Background/Purpose: As demonstrated by the negative correlation between Treg frequency or suppressive function and SLE disease activity index score, it is tempting to speculate that a Treg defect contributes to dysregulated immune response in SLE. GATA-3 is not only indispensable for Th2 differentiation, but also plays critical roles in homeostasis and function of Tregs as exemplified when Treg-specific deletion of GATA-3 leads to spontaneous development of inflammatory disorder. GATA-3 deficient Tregs have reduced FoxP3 expression and are poised to express IL-17 in the presence of IL-6. However, roles of GATA-3 in lupus Treg biology remain undefined.

Methods: CD3⁺ T cells were isolated from 9 pairs of matched SLE and healthy control (HC) subjects. A part of the CD3⁺ T cells were stained with CD4, CD8, and CD25 followed by GATA-3 and FOXP3. The rest of the cells were cultured in RPMI culture media with 10% FCS, 1% Penicillin/Streptomycin, and 1% L-glutamine for 3 days in the presence of plate-bound anti-CD3 and soluble anti-CD28 with or without 100 nM rapamycin. After 3 days of culture period, cells were stained as previously described. GATA-3 expression by CD4⁺, CD8⁺, and CD4^–CD8^– double-negative (DN) T cells as well as CD4⁺CD25⁺FOXP3⁺Treg was assessed by flow cytometry. Mean fluorescence intensity was normalized to that of HC samples on day 0. Frequency of GATA-3⁺ cells was determined after 3-day T-cell-receptor stimulation.

Results: GATA-3 was overexpressed in freshly isolated SLE CD3⁺ T cells (Relative MFI: 1.22±0.08, p=0.013), CD8⁺ T cells (Relative MFI: 1.26±0.09, p=0.012), and DN T cells (Relative MFI: 1.70±0.33, p=0.033), whereas it was reduced in freshly isolated SLE Tregs (Relative MFI: 0.81±0.09, p=0.032). After 3-day T-cell-receptor stimulation, rapamycin suppressed GATA-3 expression by CD3⁺ T cells in HC (% GATA-3⁺ cells: 51.8±1.7% in rapamycin-untreated cells, 49.7±2.2% in rapamycin-treated cells, p=0.006), which appears to be the case in SLE (% GATA-3⁺ cells: 49.8±5.6% in rapamycin-untreated cells, 48.1±6.9% in rapamycin-treated cells). In contrast, rapamycin augmented GATA-3 expression by Tregs in HC (% GATA-3⁺ cells: 63.1±4.6% in rapamycin-untreated cells, 69.4±3.7% in rapamycin-treated cells, p=0.003) and appears to have restored that in SLE (% GATA-3⁺ cells: 61.1±6.3% in rapamycin-untreated cells, 62.8±7.6% in rapamycin-treated cells).

Conclusion: The data points to GATA-3 deficiency in SLE Treg as a potential mechanism underlying the functional incompetence. Rapamycin may correct Treg function by restoring GATA-3 expression in SLE.